Mesoscale and Nanoscale Physics
Surface-Selective Probe of Spin-Triplet Superconductivity in Rhombohedral Graphene
Kilian Krötzsch, Zekang Zhou, Kryštof Kolář et al. (+6 more)
Superconductivity in rhombohedral
graphene has been observed across many layer numbers, with mounting evidence pointing toward
spin-triplet pairing, yet complementary probes of the superconducting
spin structure remain needed. Here we use one-sided WS$_2$ proximity in rhombohedral pentalayer
graphene (R5G) as a surface-selective
spin-orbit probe. The induced Ising
spin-orbit coupling is strongest for carriers localized near the WS$_2$ interface, allowing the displacement field to tune the overlap between superconducting carriers and the
spin-orbit perturbation. We observe a strongly asymmetric superconducting landscape: two robust pockets, SC1 and SC2, survive only on mutually opposite signs of displacement field, while a third pocket, SC3, is substantially weaker. Gate-tracking features,
quantum oscillations, and self-consistent band-structure calculations identify the layer polarization and
Fermi-surface character of the relevant carriers. The robust superconducting states are absent or strongly weakened when the active high-DOS carriers are polarized toward the WS$_2$ interface. Since Ising
spin-orbit coupling is compatible with time-reversed
spin-singlet pairing but competes with same-
spin intervalley triplet pairing by canting or pinning the parent
spin texture, this surface-selective suppression provides additional evidence for
spin-triplet superconductivity involving both hole-like and electron-like carriers. Our results establish one-sided TMD proximity as a displacement-field-tunable probe of superconducting
spin structure in rhombohedral
graphene.
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All authors Kilian Krötzsch, Zekang Zhou, Kryštof Kolář, Yonggen Li, Kenji Watanabe, Takashi Taniguchi, Moty Heiblum, Cyprian Lewandowski, Mitali Banerjee
Mesoscale and Nanoscale Physics
Magnetic-field control of Fermi polaron fine structure and polarization in strained monolayer semiconductors
Zakhar A. Iakovlev
The theory of attractive
Fermi polaron energy spectrum fine structure and polarization in doped two-dimensional
semiconductors in external
magnetic field is developed.
Fermi polaron $g$ factor renormalization due to correlations with the valley-polarized
Fermi sea of resident charge carriers is calculated. We study the competition between Zeeman and strain-induced splittings in monolayers under uniaxial strain. The control of strain,
magnetic field and electron density allows continuous tuning of energy splitting and eigenstate polarization. Linearly polarized strain-induced split doublet exhibits quadratic Zeeman shift changing to linear Zeeman splitting with elliptical polarization with the increase of
magnetic field. We identify a critical
magnetic field above which resident charge carriers become fully valley polarized and only one circularly polarized
Fermi polaron state remains. Within the Green's function approach we calculate energy levels and Stokes parameters of attractive
Fermi polaron states and introduce a simplified effective two-level model allowing us to study analytically the interplay of Zeeman and pseudo-Zeeman splitting. We calculate absorption and reflection spectra, including circular and linear dichroism in the trion spectral range. These results show that real and strain-induced pseudomagnetic fields provide complementary tools for controlling the optical response of many-body excitonic quasiparticles in two-dimensional
semiconductors.
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Strongly Correlated Electrons
Local magnetic order in vacancy-disrupted spin ice Ho2TiO5
Raju Baral, Haidong Zhou, Qiang Zhang et al. (+2 more)
We investigate how local
magnetic correlations evolve when the classical pyrochlore
spin-ice Ho2Ti2O7 is transformed into the partially disordered stuffed compound Ho2TiO5.
Neutron scattering measurements were analyzed using real-space
magnetic pair distribution function, reciprocal-space reverse Monte Carlo, and half-polarized
neutron powder diffraction methods to connect the average
crystal structure with local
magnetic correlations. Both compounds retain long-range $Fd-3m
symmetry, but in Ho2TiO5 this average structure distorts locally through Ho-O, Ti-O and O-O bond-length disorder associated with partial Ho/Ti occupancy. Despite this disorder, half-polarized
neutron powder diffraction shows that the Ho moments retain local <111> rangle Ising anisotropy and form
spin-in/
spin-out configurations on the tetrahedral network. In Ho2Ti2O7, real- and reciprocal-space analyses reveal a nearly ideal two-in/two-out
spin-ice state at 0.3K, with 95% of tetrahedra satisfying the ice rule, followed by progressive thermal disordering on warming. In Ho2TiO5, most tetrahedra are magnetically incomplete because some tetrahedral vertices are occupied by nonmagnetic Ti rather than Ho; nevertheless, the dominant incomplete configurations are 2-in/1-out and 1-in/2-out, which are locally compatible with the ice rule if the missing Ho
spin is restored. The single-ion <111> Ising anisotropy is therefore retained throughout, while the collective ice ordering is strongly disrupted: Ho2TiO5 is a vacancy-disrupted
spin ice in which a local ice-rule tendency persists on a topologically incomplete
magnetic network.
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All authors Raju Baral, Haidong Zhou, Qiang Zhang, Benjamin A. Frandsen, Stuart Calder
Mesoscale and Nanoscale Physics
Wavelength-Selective control of Atomic Scale Au Contacts
Werner Brämer-Escamilla, Floralba Lopez, Laila Procel et al. (+3 more)
We demonstrate wavelength-selective control of atomic motion in a mechanically controllable Au break junction. Excitation at $\lambda_{\mathrm{form}}\simeq 530~{\rm nm}$ drives gap closure and metallic bridge formation, whereas excitation at $\lambda_{\mathrm{rup}}\simeq 407~{\rm nm}$ drives neck thinning, bridge rupture, and subsequent gap opening. Unlike conventional optical switching in metallic contacts, where illumination primarily acts via thermal expansion, the present experiment reveals oppositely directed atomic drift at different wavelengths. Time-resolved conductance traces allow us to distinguish two dynamical regimes. In the tunneling regime, exponential conductance transients measure the drift velocity of the gap coordinate for both gap closure and gap opening. In the metallic regime, the Sharvin relation converts linear $\sqrt{G/G_0}$ transients into radial neck-growth and neck-thinning velocities of comparable magnitude. These results establish optically selected atomic drift as a mechanism for reversible control of metallic nanocontacts and provide a quantitative route to follow plasmon-assisted atomic rearrangements in real time.
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All authors Werner Brämer-Escamilla, Floralba Lopez, Laila Procel, David Llerena, Carlos Sabater, Ernesto Medina
Superconductivity
Two-phonon pairing and superconductivity in $SrTiO_3$
Antonio Santacesaria, Cristiano Muzzi, Maria Eleonora Temperini et al. (+3 more)
We explore the possibility that the two-
phonon pairing mechanism proposed by Ngai can explain superconductivity in doped strontium titanate (STO). The two-
phonon deformation potential is evaluated using two distinct theoretical estimates based on first-principles calculations and two empirical estimates based on experimental data, yielding very large values of the same order of magnitude. We derive the effective electron-electron interaction mediated by two-
phonon exchange. Crucial to our computations is the strong dispersion of the involved soft
phonons. Because the scale of the two-
phonon interaction is much larger than the
Fermi energy, the Migdal
theorem does not apply. We obtain a one-loop Eliashberg equation that can be solved in the weak-coupling limit. We find that despite the significant electron-
phonon matrix element, phase space considerations considerably reduce the effective coupling. A two-
phonon mechanism can not be excluded based on the $T_c$ magnitude, but its value is dominated by the high-energy-frequency physics and is weakly affected by the soft-
phonon behavior. The theory predicts a $T_c$ that monotonously increases with doping, which is not in accordance with the experiment. We identify the conditions for a two-
phonon mechanism to be effective in other materials and discuss possible candidates.
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All authors Antonio Santacesaria, Cristiano Muzzi, Maria Eleonora Temperini, Paolo Barone, Maria N. Gastiasoro, José Lorenzana
Materials Science · Cross-listed from physics.optics
Self-Focusing Control for Depth-Precise Wafer Slicing of 4H-SiC in Femtosecond Laser Processing
Dong Hee Kang, Jaeseung Lim, Mishfaqur Rahman et al. (+4 more)
4H-SiC has emerged as a third-generation chip material because its superior thermal conductivity and high breakdown field enable the material to achieve high power density and higher switching frequencies in power-electronics applications. As chip architectures evolve toward 3D and heterogeneous integration, the mechanical and thermal design space tightens while yield risks grow. In particular, advanced packages require mid-process wafer thinning to < 100 $\mu$m to shorten interconnects and control thermo-mechanical stress. Femtosecond
laser slicing for 4H-SiC wafers offers a non-contact processing approach to produce thin layers with low defects, while strong optical nonlinearities obscure the relationship between the
laser parameters and the resulting slicing quality. Here, we systematically investigate Kerr-induced self-focusing using a femtosecond
laser in 4H-SiC slicing by combining experiments, a semi-empirical analytical model, and numerical ray optics simulations. We demonstrate that the interplay between pulse energy and processing depth governs the self-focusing behavior, which directly correlates with post-separation surface texture parameters and separation stress, thereby linking nonlinear beam propagation to slicing quality. Based on this relationship, we define a processability map in the pulse energy with self-focusing depth space over a normalized irradiance background. Analytically, the model extends the Marburger formula to focused beams by replacing the power ratio with a normalized irradiance. Ray optics simulations capture the
geometric features at the self-focusing point and are validated against experimental observations. Within physically defined thresholds, the processability map directly connects
laser parameters to separation stress and surface texture metrics, providing practical guidance for depth control beyond trial-and-error.
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All authors Dong Hee Kang, Jaeseung Lim, Mishfaqur Rahman, Seongheum Han, Jae-Hak Lee, Seungman Kim, Jihoon Jeong
Mesoscale and Nanoscale Physics
Controllable interaction between photons and distant spins via vacuum Rabi oscillations
Xiao Xue, Jurgen Dijkema, Tobias Bonsen et al. (+7 more)
Vacuum Rabi oscillations between a single
photon and a single
spin demonstrate the capability of harnessing light-matter interaction at the level of a single
quantum of energy. Since the observation of strong
spin-
photon coupling in gate-defined
quantum dots, probing this interaction in the time-domain has been a major objective. Here, we carefully engineer a device composed of two spatially separated double
quantum dots hosting single electron
spin qubits and a superconducting cavity to accommodate microwave
photons. We observe multiple
vacuum Rabi oscillations between each
spin qubit and the cavity. By concatenating
vacuum Rabi oscillations involving the two
spins, an energy excitation in one
qubit can be emitted as a
photon and then transferred to the other
qubit. When a single
photon is emitted, the cavity is prepared in a Fock state, leading to an accelerated
vacuum Rabi frequency. These results serve as building blocks not only in exploring light-matter interactions, but also in interfacing
semiconductor spin qubits to photonic links.
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All authors Xiao Xue, Jurgen Dijkema, Tobias Bonsen, Patrick Harvey-Collard, Maximilian Rimbach-Russ, Sander L. de Snoo, Guoji Zheng, Amir Sammak, Giordano Scappucci, Lieven M. K. Vandersypen
Materials Science
Generalized Space Groups from Internal Configuration Spaces
Zeying Zhang, Zhenye Li, Zhi-Ming Yu et al. (+2 more)
We develop a unified construction of generalized space groups for
crystals with unconventional internal degrees of freedom. Starting from the full group $G_P$ of allowed internal transformations and the stabilizer $P$ of a reference object, we determine the pointwise and setwise
symmetries, $J$ and $K$, of the allowed configuration set. Goursat's lemma then couples the internal quotient $K/J$ to a spatial quotient. The framework includes ordinary,
magnetic,
spin, and color space groups as special cases. As an example, we consider a dodecahedral object with $P=I\simeq A_5$, for which we obtain the nontrivial pair $T\triangleleft O$ with $O/T\simeq\mathbb Z_2$. The resulting generalized space group hosts a point node with topological charge $|C|=12$.
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All authors Zeying Zhang, Zhenye Li, Zhi-Ming Yu, Gui-Bin Liu, Yugui Yao
Materials Science
Physics-Informed Machine Learning for Refractory Alloy Design
Blaise Awola Ayirizia, Bimal K C and Jorge A. Munoz San Martin
Refractory complex concentrated
alloys (CCAs) exhibit exceptional mechanical properties at elevated temperatures, but their vast compositional space (approximately 10^15 possible combinations) poses significant challenges for experimental exploration. We develop a physics-informed machine learning framework combining
quantile gradient boosting with Born stability constraints to predict eight mechanical properties (bulk modulus B, shear modulus G, Vickers hardness Hv, elastic constants C11, C12, C44, Young's modulus E, and Poisson's ratio nu) of refractory CCAs. Using 393 density functional theory (DFT)-computed
alloys from a 10-element design space (Cr, Hf, Mo, Nb, Re, Ta, Ti, V, W, Zr), we achieve coefficient of determination (R^2) values of 0.89 to 0.97 with mean absolute errors of 0.85 to 14.74 GPa across six properties on a held-out test set (n = 59). Remarkably, all test predictions satisfy the Born stability criteria (100% compliance), demonstrating the efficacy of physics-informed constraints. Compositional screening in valence electron concentration (VEC)-atomic size mismatch (delta) space identifies high-performance candidates, with MoReW exhibiting the highest predicted shear
rigidity (C44 = 139 GPa). Elemental analysis reveals that rhenium appears in 100% of the top-performing
alloys, molybdenum in 90%, and chromium in 80%, establishing quantitative design rules: VEC = 6.0 to 6.4, delta < 10%, and Re-Mo-Cr ternary systems maximize shear resistance. This physics-informed screening framework enables accelerated discovery of mechanically stable, high-performance refractory
alloys from the trillion-scale compositional space.
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Materials Science
From phase transformation to amorphization: damage accumulation in Yb-implanted $\beta-Ga_2O_3$
Joanna Matulewicz, Renata Ratajczak, Ewa Grzanka et al. (+11 more)
This study provides a comprehensive analysis of the radiation response and structural
evolution of differently oriented$\beta-Ga_2O_3$ single
crystals subjected to Yb ion implantation over a wide fluence range from $5 \times 10^{12}$ to $1 \times 10^{16}$~cm$^{-2}$ ($0.04$–$74$~dpa). A multi-technique approach (RBS/c, PAS, HRTEM, and HRXRD) was employed to investigate the mechanisms of damage accumulation. The results reveal a multi-stage process of defect
evolution. At a critical threshold of around $0.4$~dpa, the accumulation of
lattice strain triggers a phase transformation from monoclinic $\beta$-Ga$_{2}$O$_{3}$ to a defective spinel structure of $\gamma$-Ga$_{2}$O$_{3}$. Notably, the formation of this new phase is accompanied by strain relaxation. With further irradiation, defects develop within the
crystal structure of $\gamma$-Ga$_{2}$O$_{3}$. The associated atomic reorganization at this stage is reflected by a distinct dip in the damage accumulation curve and the appearance of stacking faults in the subsurface region of the implanted layer. In contrast to previous reports suggesting high radiation stability of this phase, the present study clearly demonstrates that continuous defect accumulation results in a significant increase in both displaced atoms and vacancy-type defects, with a strong depth dependence in their type and density. Ultimately, at an irradiation level of approximately $7$~dpa, the surface layer amorphizes. With further irradiation, the amorphous layer expands, gradually replacing the transient $\gamma$-Ga$_{2}$O$_{3}$ phase. These findings reveal that the radiation tolerance of gallium
oxide is highly sensitive to ion-specific interactions and strain-induced instabilities, thereby challenging the previously assumed robustness of this material under high-fluence ion irradiation.
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All authors Joanna Matulewicz, Renata Ratajczak, Ewa Grzanka, Maciej Oskar Liedke, Damian Kalita, Eric Hirschmann, Andreas Wagner, Mikolaj Grabowski, Michal A. Strozyk, Cyprian Mieszczynski, Przemyslaw Jozwik, Ulrich Kentsch, Rene Heller, Frederico Garrido
Soft Condensed Matter
Geometry-Controlled Motility of Microswimmers in elementary microfluidic confinements
Marvin Brun-Cosme-Bruny, Philippe Peyla and Salima Rafai
The motility of microswimmers in confined environments is a fundamental problem in active matter physics, with direct implications for microfluidic applications and the understanding of microorganism behavior in complex natural habitats. Although the run-and-tumble dynamics of flagellated microalgae such as Chlamydomonas Reinhardtii (CR) are well characterized in bulk suspension, the extent to which elementary
geometric confinements alter their swimming remains insufficiently understood, particularly regarding the relative contributions of steric contact versus hydrodynamic interactions. Here, we experimentally investigate the trajectories of individual CR
cells in a diversity of PDMS microfluidic geometries of growing complexity using single-particle tracking and statistical analysis. We show that
cells in straight channels accumulate near walls and align along the channel axis, a behavior qualitatively reproduced by steric Active Brownian Particle simulations, yet showing a confinement-dependent velocity enhancement consistent with hydrodynamic wall coupling. In circular cavities with diameter below the persistence length L_0 ~350 microns,
cells transition from bulk active Brownian exploration to quasi-circular wall-following trajectories. In dumbbell geometries, inter-compartment dwell length reflect purely
geometric predictions, evidencing no measurable hydrodynamic contributions even for strong confinements. Together, these results demonstrate that environmental geometry can selectively amplify or suppress motility modes in active biological suspensions, opening avenues for the passive control of microswimmer transport in engineered microfluidic networks.
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Strongly Correlated Electrons
Antisymmetric Dynamical Spin Correlations: Spin-Space-Group Constraints and Frequency-Moment Sum Rules
Tsutomu Momoi
Polarized inelastic
neutron scattering probes the handedness of
magnetic excitations through the
spin-component-antisymmetric part of the dynamical
spin-structure-factor tensor. We derive its
symmetry constraints under
unitary and antiunitary residual operations of
magnetic space groups and
spin-space groups. These constraints determine the allowed tensor components, their parity under momentum reversal, and
symmetry-enforced nodes. We then introduce the corresponding antisymmetric commutator spectral function and derive exact zero-temperature sum rules for its frequency moments. The zeroth moment is fixed by the uniform magnetization. For Heisenberg or XXZ exchange
Hamiltonians, the first moment of the $xy$ component is fixed by a momentum-weighted static vector chirality. For compensated collinear antiferromagnets, the antisymmetric dynamical structure factor is forbidden when inversion or a translation relates the opposite-
spin sublattices. In rotation-related altermagnets, however, an $xy$ component that is even under momentum reversal is allowed at generic wave vectors. Finite antisymmetric spectral weight can therefore coexist with vanishing zeroth and first moments of the commutator spectral function. In a planar helix, by contrast, a residual antiunitary
spin-space-group
symmetry makes the allowed $xy$ component odd under momentum reversal. Its first moment is generally nonzero and is fixed by a momentum-weighted static vector chirality through the first-moment sum rule. Linear
spin-wave calculations for representative altermagnetic and helical models explicitly realize these
symmetry and sum-rule constraints.
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Disordered Systems and Neural Networks
Analytical results of Typical Medium Theory for the Bethe lattice with Cauchy disorder
A. Östlin, I. Titvinidze, M. Kollar et al. (+2 more)
We present a combined numerical and analytically tractable realization of the typical medium theory (TMT) for Anderson localization on the infinite-connectivity Bethe
lattice with Cauchy-distributed on-site disorder. Exploiting the special properties of the Cauchy distribution and the Bethe
lattice, we derive an analytical expression for the typical density of states (TDOS) and obtain a simplified TMT self-consistency scheme. We show that the TDOS at the band center decreases linearly with disorder strength and vanishes at the critical disorder $W_c=D/2$. The resulting $\omega$–$W$ phase diagram reveals the continuous collapse of the mobility edge and the disappearance of extended states.
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All authors A. Östlin, I. Titvinidze, M. Kollar, D. Jones, L. Chioncel
Materials Science
Guided Synthesis of EMT Zeolites by Machine Learning
Emmanuel A. Olanrewaju, Santosh Adhikari, Zhiyin Niu et al. (+4 more)
Zeolites are microporous crystalline materials with diverse frameworks, widely used in industrial applications such as petroleum refining and molecular separation. Unlike most zeolites, EMT can be synthesized under mild conditions (at low temperatures and without the use of organic structure-directing
agents), making it attractive for cost-effective and environmentally sustainable production. However, the specific synthesis conditions that selectively produce EMT rather than similar frameworks like FAU are not yet well established. In this work, we develop machine learning (ML) models to guide the discovery of synthesis conditions for EMT zeolites. Our
dataset comprises 174 experimental synthesis attempts, recording reaction time, temperature, silica and alumina sources, Si/Al stoichiometric ratio, and other synthesis parameters. We apply both classical ML methods and pretrained foundation models to predict zeolite framework outcomes from these synthesis parameters. Feature importance analysis identifies critical parameters for EMT formation, validating known synthesis principles. Leveraging the ML models, we explore the synthesis space and identify six promising new conditions for EMT formation. Experimental validation confirms EMT crystallization in five cases, including two with Si/Al stoichiometric ratios outside the training
dataset's range. Evaluation on independent literature-reported synthesis conditions further demonstrates the generalizability of the model. This work demonstrates a data-driven approach to accelerating zeolite synthesis, closing the loop between ML prediction and experimental validation.
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All authors Emmanuel A. Olanrewaju, Santosh Adhikari, Zhiyin Niu, Michael Nikolaou, Jeremy C. Palmer, Jeffrey D. Rimer, Mingjian Wen
Disordered Systems and Neural Networks
A Spectral Route to Directed-Polymer Glasses
Sen Mu, Abbas Ali Saberi and Mehran Kardar
A finite density of mutually avoiding directed
polymers in a quenched random medium is a minimal model of glassy line matter. The dilute theory, solved by replica Bethe ansatz, predicts an interaction free energy proportional to $\rho^2$ and disorder cumulants with distinct power-law dependences on the density $\rho$, but direct numerical tests have been hindered by the combinatorially large many-
polymer transfer
matrix. We recast the problem as filling logarithmic
eigenvalues of a single-
polymer transfer-
matrix product, obtaining the quenched free energy, its cumulants, and a disorder-induced linear spectral edge consistent with the replica prediction.
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Soft Condensed Matter
Synthetic paracrine signaling of colloids drives self-assembly limit cycles
Tim E. Veenstra, René van Roij, Pepijn G. Moerman et al. (+1 more)
Developing synthetic materials that exhibit life-like behavior, such as internally driven cycles, remains a central challenge in active matter. Here, we introduce a minimal colloidal model of chemical signaling in which particles produce diffusing signaling molecules that selectively promote or inhibit attractive interactions among neighboring particles. This bio-inspired, paracrine-like signaling mechanism generates context- and history-dependent many-body interactions that break time-reversal
symmetry and drive the system far from
equilibrium, leading to the spontaneous emergence of autonomous, internally sustained limit cycles in the composition of particle clusters. Using computer simulations, we map the resulting nonequilibrium phase behavior and identify distinct dynamical regimes controlled by the rates of signal production and degradation, together with the
diffusion range of the signaling molecules. Among these, we find a robust oscillatory state in which particle clusters autonomously assemble in a cyclic fashion, driven entirely by internal feedback loops. Our results establish paracrine-signaling colloids as a minimal, physically realizable platform for programmable nonequilibrium materials with life-like functionality and provide a general route toward synthetic active matter with self-regulated collective dynamics.
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All authors Tim E. Veenstra, René van Roij, Pepijn G. Moerman, Marjolein Dijkstra
Strongly Correlated Electrons
Cavity control of quantum phase transitions in a two-dimensional Kondo lattice
Jun Mochida, Atac Imamoglu and Yuto Ashida
Cavity
quantum electrodynamics offers a route to control
quantum phases by using
vacuum fluctuations of confined electromagnetic fields. In particular, planar cavities based on polar van der Waals materials can generate strongly confined modes and are promising for controlling two-dimensional correlated materials. Recently, moiré materials have become central platforms for studying two-dimensional heavy-
fermion systems and their
quantum phase transitions. Kondo
lattices provide a prototypical model for studying
quantum phase boundaries, driven by competition between Kondo screening and the ordering of local
magnetic moments. We show that a cavity-induced interaction can shift the
quantum phase transitions between a heavy-
fermion phase and an
antiferromagnetic phase in a two-dimensional Kondo
lattice through a momentum-dependent self-energy of the conduction bands. For the longitudinal projected field motivated by h-BN
hyperbolic phonon polaritons, the self-energy favors Kondo hybridization and expands the heavy-
fermion region. Transverse and circular in-plane model structures give distinct effects, with the transverse case relatively favoring the magnetically ordered phase and the circular case lying between the longitudinal and transverse cases. These results indicate that electromagnetic
vacuum fluctuations can effectively modify the control parameters of strongly correlated two-dimensional Kondo materials.
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Strongly Correlated Electrons · Cross-listed from hep-th
Gabriel Cuomo, Simone Giombi and Luigi Tizzano
The lightlike Wilson line cusp underlies the Sudakov double logarithm and is a central ingredient in gauge-theory factorization. We ask what replaces this behavior for general conformal line defects in Lorentzian signature. We argue that, when the defects admit local endpoint operators, the cusp anomalous dimension has a finite large-boost limit fixed by the scaling dimensions of the corresponding defect-creation operators. We further analyze the distinct analytic continuations of the cusp, elucidate their physical interpretations, and derive a positivity condition on the Lorentzian cusp anomalous dimension. We test these predictions in several perturbative examples, including pinning-field defects and
spin impurities, and discuss their possible implications for gauge theories.
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Materials Science
Machine Learning-Guided Screening of Advantageous Solvents for Solid Polymer Electrolytes in Lithium Metal Batteries
Jiadong Shen, Junjie Chen, Xiaosa Xu et al. (+8 more)
Trace residual solvents in solid
polymer electrolytes (SPEs) significantly affect electrolyte and interface properties, where optimal selection enhances ionic conductivity and transference numbers. However, solvent complexity hinders general screening methods. We establish a universal criterion linking electronic (HOMO, LUMO) and macroscopic properties (dielectric constant, dipole moment, polarizability) via machine learning on an approximately 10,000-solvent
dataset from high-throughput DFT. Two solvents, N-methoxy-N-methyl-2,2,2-trifluoroacetamide and 2,2,2-trifluoro-N,N-dimethylacetamide, were identified. Experimental incorporation of trace N-methoxy-N-methyl-2,2,2-trifluoroacetamide into a poly(vinylidene fluoride-co-hexafluoropropylene)
matrix achieves a 4.5 V window, 5.5x10^-4 S cm^-1 conductivity (30 C), and 0.78 Li+ transference number. The
cell retains 86.7% capacity over 500 cycles (LiFePO4) and 98.7% after 200 cycles at 2C (LiNi0.9Co0.05Mn0.05O2), outperforming 2,2,2-trifluoro-N,N-dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone, and dimethyl sulfoxide. This synergy enables balanced ion transport, wide stability, and cycling durability, advancing safer, high-energy lithium metal batteries. Our integrated approach establishes a solvent screening paradigm for rational SPE design, accelerating next-generation battery development.
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All authors Jiadong Shen, Junjie Chen, Xiaosa Xu, Jin Li, Zhenyu Wang, Pengzhu Lin, Zixiao Guo, Yu Wang, Jing Sun, Baoling Huang, Tianshou Zhao
Mesoscale and Nanoscale Physics
Machine Learning Bandgap Prediction of Nanoporous Graphenes with Water
Sneha Mittal, Alan E. Anaya Morales, Victor Rosendal et al. (+1 more)
The structure and dynamical behavior of water confined at or within nanostructures is a topic central to many fields, from biology to emerging electronics such as carbon nanostructures. Nanoporous
graphene (NPG) containing periodic nanoscale pores with specific
topologies has emerged as a promising material in carbon-based nanoelectronics; however, its interaction with ambient water remains poorly understood. Here, we combine density functional theory (DFT), ab initio molecular dynamics (AIMD), and interpretable machine learning (ML) to reveal how water controls
quantum transport in NPGs. Depending on the local hydration structure, the bandgap varies by more than a factor of two across NPG and nitrogen-doped hybrid (h-NPG) systems. To uncover the underlying mechanism, we develop Smooth Overlap of Atomic Positions (SOAP)-based black-box and physics-informed grey-box ML models. The Gaussian process regression model achieves near-DFT accuracy while enabling physical interpretation. Analysis identifies water dipole orientation, water-substrate distance, water center-of-geometry, and ribbon-resolved dipole moments as the dominant factors controlling bandgap modulation across NPG and h-NPG systems.
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All authors Sneha Mittal, Alan E. Anaya Morales, Victor Rosendal, Mads Brandbyge
Strongly Correlated Electrons
Microscopic Origin of Random Singlet Behavior in B-site Disordered Spin-1/2 Perovskite BaCu_1/3Nb_2/3O_3 Revealed by EXAFS and Thermodynamics
Sagar Mahapatra, Francesco De Angelis, Martin Etter et al. (+5 more)
We report a combined structural and thermodynamic study of the ABO$_3$-type disordered perovskite BaCu$_{1/3}$Nb$_{2/3}$O$_3$ (BCNO), whose B site is jointly occupied by Cu and Nb in the $1:2$ ratio. Using synchrotron powder x-ray diffraction (XRD) and x-ray absorption fine structure (XAFS) spectroscopy, we investigate the microscopic nature of Cu$^{2+}$/Nb$^{5+}$ disorder on the pseudo-cubic B-sublattice and its relation to the emergent random-singlet (RS) behavior evidenced at low temperatures. While XRD reveals no long-range Cu/Nb ordering and average site occupancy consistent with stoichiometry, XAFS reveals a peculiar local chemical order characterized by preferential heteroatomic Cu$:$Nb correlations. This local arrangement strongly suppresses direct Cu$:$Cu linkages, despite the Cu concentration being close to the percolation threshold of a cubic
lattice. The resulting exchange network explains the absence of
spin-glass freezing or long-range
magnetic order in the presence of substantial
antiferromagnetic interactions, as indicated by a Curie-Weiss temperature $\Theta_{CW}\approx -50$ K. Instead, the
magnetic susceptibility $\chi(T)$ and specific heat $c_p(T)$ exhibit power-law behavior and characteristic single-parameter $T/H$ scaling over broad temperature and
magnetic-field ranges, consistent with random-singlet phenomenology. Notably, at very low temperatures, the specific heat behavior transitions from $T^{1-\gamma}$ ($\gamma \approx 0.6$ from the $T/H$ scaling) in zero-field to a T-linear dependence under high field, indicating a crossover to a distinct low-energy regime whose microscopic origin remains to be established.
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All authors Sagar Mahapatra, Francesco De Angelis, Martin Etter, Edmund Welter, M. P. Saravanan, Rajeev Rawat, Carlo Meneghini, Surjeet Singh
Quantum Gases
Quantum Impurities as Probes of Finite-Temperature Fluctuations in Two-Dimensional Bose Gases
Victor Velasco, Gabriele Spada, Giovanni Midei et al. (+2 more)
Two-dimensional
quantum gases provide a distinctive setting in which enhanced thermal fluctuations, finite-size effects, and two-body bound-state formation are intrinsically intertwined. In this work, we study a single attractive
impurity immersed in a finite, weakly interacting two-dimensional Bose gas, where finite size stabilizes a nonzero condensate fraction by introducing an infrared momentum scale, thereby enabling a Bogoliubov description of the bath. Using a hybrid approach that combines finite-temperature many-body scattering theory with input from path-integral Monte Carlo, we analyze the
impurity quasiparticle energy across the condensate and normal regimes. The infrared scale generates a
phonon-activation temperature below which the
impurity energy remains nearly temperature independent. Once the resolved
phonon modes become thermally populated, their contribution competes with condensate depletion, producing a nonmonotonic temperature dependence of the polaron energy. These results suggest that attractive Bose polarons may serve as sensitive probes of finite-size thermal fluctuations,
phonon dressing, and bound-state physics in low-dimensional Bose gases.
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All authors Victor Velasco, Gabriele Spada, Giovanni Midei, Andrea Perali, Luis A. Peña Ardila
Materials Science
Epitaxial SiGeSn alloys for CMOS-compatible thermoelectric devices
Patrizio Graziosi, Damiano Marian, Andrea Tomadin et al. (+7 more)
The integration of thermoelectric devices into mainstream microelectronic technological platform could be a major breakthrough in various fields within the so-called Green-IT realm. In this article, the thermoelectric properties of heteroepitaxial SiGeSn
alloys, a novel CMOS compatible material system, are evaluated to assess their possible application in thermoelectric devices. To this purpose, starting from the experimentally low
lattice thermal conductivity of SiGeSn/Ge/Si layers of about $\sim$1-2 W/m$\cdot$K assessed by means of 3-$\omega$ measurements, the figure of merits are calculated through the use of Boltzmann transport equation, taking into account the relevant inter-valley scattering processes, peculiar of this multi-valley material system. Values for the figure of merit $ZT$ exceeding $1$ have been obtained for both p- and n- type material at operating temperatures within the 300—400 K range, i.e. at a typical On-Chip temperatures. In this interval, the predicted power factor also features very competitive values of the order of 20 $\rm{\mu W/cm\cdot K^2}$. Our finding indicates that this new class of Si-based materials has extremely good prospects for real-world applications, and can further stimulate scientific investigation in this ambit.
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All authors Patrizio Graziosi, Damiano Marian, Andrea Tomadin, Stefano Roddaro, Omar Concepción, Johnny Tiscareño-Ramírez, Agnieszka Anna Corley-Wiciak, Dan Buca, Giovanni Capellini, Michele Virgilio
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Entangling Topological Invariants
Kazuki Ikeda and Yaron Oz
An isolated occupied multiplet may admit local tensor-product descriptions without a globally consistent subsystem structure. We characterize the obstruction by comparing the transition functions of the occupied multiplet with those generated by independent basis changes in the two candidate subsystems. When a decomposition into rank-one sectors over a closed surface is specified, the resulting quotient removes row- and column-additive Chern data and yields mixed Chern classes. Momentum-dependent mixing of the sector labels adds the Gauss–Codazzi
curvature of the moving lines, while in the label-conserving limit the mixed class is measured by a crossed Thouless pump. When only the factor dimensions $p$ and $q$ are specified, the comparison is made at the level of the clutching map of a rank-$pq$ bundle over $S^4$. Product frames generate winding numbers in $q\mathbb Z+p\mathbb Z$, so global factorization is possible exactly when $C_2$ is divisible by $\gcd(p,q)$; in particular, odd $C_2$ obstructs a $2\times2$ factorization. We illustrate the two settings with finite eight-level
Hamiltonians and give pumping and occupied-projector
tomography protocols for their readout.
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Mesoscale and Nanoscale Physics
Enhancement of far-field thermal emission via polaritonic cavity modes
Maelie Coral, Jose Ordonez-Miranda, Georges Hamaoui et al. (+5 more)
Controlling thermal emission is crucial for applications involving thermophotovoltaics, thermal sensing, imaging, and camouflage. While prior studies focused on the emission of thermally excited guided modes (TEGMs) inside cavities, their contribution to the far-field radiation outside cavities has remained unexplored. Here, we demonstrate a tunable far-field thermal channel enabled by TEGMs arising from the coupling of surface
phonon-polaritons and cavity resonances. By combining infrared emissivity experiments with fluctuational electrodynamics simulations, we identify distinct spectral features marking the conversion of two-dimensionally confined polaritonic modes into three-dimensional radiative channels. We find that silicon cavities covered with SiO2 enhance the emissivity by up to 200% near the polaritonic spectral resonance, whereas bare silicon cavities yield only broadband enhancement. These findings provide experimental evidence of TEGMs and establish a simple cavity architecture as an effective and scalable platform for tailoring thermal radiation without complex nanofabrication.
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All authors Maelie Coral, Jose Ordonez-Miranda, Georges Hamaoui, Roman Anufriev, Laurent Jalabert, Masahiro Nomura, Yannick De Wilde, Sebastian Volz
Statistical Mechanics
Lower bounds on entropy production from dynamical correlation functions
Paul Raux, Alexander M. Maier and Udo Seifert
Entropy production is a key property in
stochastic thermodynamics. For partially observed and coarse-grained systems, its inference is challenging and typically rests on proven lower bounds. We derive two versions of such bounds based on the asymmetry of experimentally accessible two-time correlation functions of coarse-grained state observables. For non-
equilibrium steady states, the bound is valid for arbitrary correlation lag. For time-dependent processes, it requires the limit of vanishing lag. These bounds hold true for any system that follows either a Markovian dynamics or a coupled set of overdamped Langevin equations on some underlying, unobservable level of description. We illustrate the bounds for both types of dynamics and discuss their optimization and potential tightness.
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Materials Science
Toward two dimensional MoS2 electrets
Eugenio Lunedei, Andrea Liscio, Francesco Borgatti et al. (+8 more)
Here, we show that controlled sulfur vacancy engineering converts monolayer MoS2 into an electret, imparting the ability to store quasi-permanent electrostatic charge within a single atomic layer. Sulfur vacancies are generated with submicrometer spatial control by stamp-assisted electrode-free electrochemical nanolithography, yielding programmable defect densities from 10 10 to 10 13 1 cm-2. The resulting vacancy domains act as deep electron traps and produce surface charge densities up to 1 uCcm-2, with charge retention in the order of hundreds days under ambient conditions. Kelvin probe and electric force microscopies directly reveal stable electrostatic patterns that replicate the lithographic motif. The same vacancy landscape simultaneously defines
exciton-quenching regions, generating co-localized optical and electrostatic contrast and reducing the apparent
exciton lifetime from 15 ns to 180 ps through enhanced nonradiative recombination. The persistence of the optical response over one year identifies sulfur vacancies, rather than transient charge states, as the origin of the patterned functionality. These results establish defect-engineered MoS2 as the first two-dimensional electret and demonstrate that atomic vacancies can be exploited as functional elements for encoding electrostatic and excitonic behavior in a single atomic layer.
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All authors Eugenio Lunedei, Andrea Liscio, Francesco Borgatti, Edoardo Chini, Pasquale DAngelo, Fiorenza Esposito, Niccolo Borghi, Matteo Mannini, Denis Gentili, Luca Seravalli, Massimiliano Cavallini
Soft Condensed Matter
Theory of Handedness Selection in Helices of Chiral Polymers and Biopolymers
Biman Bagchi
Helices are among the most common ordered structures in biological and synthetic
polymers, but their formation involves more than local conformational preference. A finite helix must nucleate, grow, resist breaking, and maintain a selected handedness against thermal fluctuations. We develop a three-state Ising-like transfer-
matrix theory in which each segment is coil-like, right-handed helical, or left-handed helical. This formulation separates ordinary helix–coil cooperativity from the persistence of handedness. The right–left symmetric problem decomposes into symmetric and antisymmetric sectors, giving two characteristic lengths: the helical correlation length $\xi_H$ and the
chiral persistence length $\xi_\chi$. In the strongly helical rare-wall limit, $\xi_\chi\simeq (1/2)\exp[\beta(K+J)]$. A local
chiral bias, motivated by the Ramachandran landscape, is then amplified over finite helical domains.
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Materials Science
Strain Tuning of Orbital-Driven Giant Magnetoresistance in van der Waals ferrimagnet Mn$_3$Si$_2$Te$_6$
Abdul Ahad, Miuko Tanaka, Shunta Aoki et al. (+7 more)
Strain engineering of magnetotransport offers a powerful strategy for uncovering emergent electronic and domain phenomena in
quantum magnetic materials, while providing a promising pathway toward next-generation mechanically programmable spintronic technologies. Van der Waals magnets are particularly attractive in this context because their high crystallinity and mechanical flexibility allow exceptionally large, precisely controllable strain, enabling access to strain-induced functionalities unattainable in conventional solids. Here, we report systematic strain control of the van der Waals magnet Mn$_3$Si$_2$Te$_6$, which exhibits an unconventional colossal magnetoresistance whose microscopic origin remains under debate. We demonstrate in situ large-strain modulation of the electrical resistance in bulk
crystals and show that the effect can be consistently explained by strain-tunable
chiral orbital-current domains. Furthermore, measurements on exfoliated flake devices containing a single
chiral domain reveal direct strain control of the electronic structure affected by orbital
magnetic moment, establishing a unified microscopic mechanism for the unconventional colossal magnetoresistance. These results identify strain as an exceptionally effective control parameter for tailoring electronic and
magnetic states in van der Waals magnets and provide a conceptual framework for realizing
spin-straintronic functionalities based on orbital degrees of freedom.
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All authors Abdul Ahad, Miuko Tanaka, Shunta Aoki, Darius-Alexandru Deaconu, Varun Shah, Tenta Kitamura, Hao Ou, Mohammad Saeed Bahramy, Jiang Pu, Toshiya Ideue
Soft Condensed Matter
Control of collective activity to crystallize an oscillator gas
Marine Le Blay, Joshua H.K. Saldi and Alexandre Morin
Motility-induced phase separation occurs in assemblies of self-propelled units when activity is coupled negatively to density. In contrast, the consequences of a positive coupling between density and activity on the collective behaviour of active matter remain unexplored. Here, we show that collective activity can emerge from such a positive coupling among non-motile building blocks. We perform experiments with self-sustained oscillators powered by contact-charge electrophoresis. Although the oscillators are non-motile by design, they spontaneously form an active gas when confined together. The super-elastic nature of collisions constitutes a positive density-activity coupling and underlies the active gas properties. Elucidating the origin of binary collisions allows us to precisely control the structure of the active gas and its eventual crystallization. Beyond considering the overlooked positive coupling between density and activity, our work suggests that rich collective properties can emerge not only from the
symmetry of interactions between active building blocks, but also from their adaptable and responsive behaviour.
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