Materials Science · Cross-listed from physics.optics
Plasma Etch Process Optimization for Photonic-Grade Diamond-on-Insulator Substrates and Thickness Evaluation using Colorimetry
Tianyin Chen, Alessio Miranda, Leyla Rami et al. (+2 more)
Diamond color-center
qubits integrated with photonic
circuits can be initialized, manipulated, entangled, and read individually with high fidelity, making them attractive for large-scale modular
quantum computers,
quantum networks, and distributed
quantum sensing. However, the limited size of heteroepitaxially grown single-
crystal diamond (SCD) and photonic-grade diamond-on-
insulator (DOI) substrates remains a challenge for integration with existing manufacturing processes. Here, we develop a
plasma etch recipe to thin direct-bonded (100) SCD membranes (<50 $\mu$m) into large-area, thin-film DOI substrates, and demonstrate free-standing photonic chiplets fabricated from the resulting DOI. The ICP-RIE recipe preserves diamond bonding, provides sufficient micromasking and surface-quality control, and enables thin-film DOI manufacture. We thin a 10 $\mu$m diamond plate bonded to SiO$_2$/Si and obtain a photonic-grade DOI substrate with diamond thickness $\leq$300 nm. The DOI film is around 300 nm thick over 0.5 $\times$ 0.5 mm$^2$, with surface roughness < 0.5 nm, while the bonding interface remains intact. Diamond photonic chiplets are fabricated on this DOI substrate using a standard two-step lithography process, without complex thin-film transfer, under-etching, or pedestal formation. We also present a colorimetric study of diamond visibility on SiO$_2$ and quantify color differences across thicknesses in common colorimetric spaces. This analysis enables automatic diamond-thickness extrapolation from standard optical microscope images with 5 nm resolution, in good agreement with white-light interferometry (WLI) measurements. The DOI substrate and colorimetric thickness-evaluation method provide an effective fabrication platform and reliable validation route for scalable manufacturing of diamond nanophotonic devices, opening a path toward large-scale integrated
quantum systems.
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All authors Tianyin Chen, Alessio Miranda, Leyla Rami, Ryoichi Ishihara, Salahuddin Nur
Strongly Correlated Electrons
Superconductivity and non-Fermi liquid metals in a charge-1/3 anyon fluid
Zhengyan Darius Shi and T. Senthil
We revisit the charge-1/3 anyon fluid obtained by doping the $\nu = 2/3$ Jain fractional Chern
insulator (FCI). In the standard composite
fermion description, the doped anyons fractionalize into three translation-related
flavors of secondary composite
fermions, whose gauge-mediated interactions drive a robust inter-
flavor pairing instability. In our previous work, we analyzed a
flavor-asymmetric paired state and obtained a charge-ordered
Fermi liquid. Inspired by a recent paper, we consider an alternative
flavor-symmetric paired state and show that it is an SC* state: a charge-$2e$ condensate that coexists with residual $\mathbb{Z}_2$ topological order. The weak and strong pairing regimes share the same intrinsic topological order but differ in
chiral central charge, giving $c_- = 7/2$ and $c_- = 2$. We further show how other proposed effective field theories fit within the same composite
fermion description, and argue that across the doping driven FCI-to-
superconductor transition, localized anyons evolve into Bogoliubov quasiparticles rather than
vortices. At low doping, we identify an approximate SU(3)-symmetric regime in which the system instead realizes a non-
Fermi liquid $\mathbb{Z}_3$ Orthogonal Metal with three charge-1/3
fermion pockets and no sharp electron quasiparticle. Finally, we comment on the energetics of various possible ground states and discuss implications for experiments in moire materials.
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Statistical Mechanics · Cross-listed from quant-ph
Interaction geometry and ground-state properties of sparse quantum lattice models
Alex Gunning, Sebastian Schmid, Zhengxiao Liu et al. (+3 more)
We investigate how interaction geometry shapes the low-energy phases of sparse tunable long-range
quantum models. We focus on a class of graphs whose degree grows logarithmically with system size, and show how
symmetry and frustration in graph connectivity can drive, suppress, and reshape ground-state phase transitions. The central examples are power-of-$p$ graphs, where even and odd values of $p$ exhibit qualitatively distinct behaviour: even-$p$ graphs inherit the rich phase structure of the power-of-two model, while odd-$p$ graphs are governed by
geometric frustration. Fibonacci graphs provide a contrasting case, lacking the discrete self-similarity of the power-of-$p$ family but exhibiting a direct
geometric mapping between the short- and long-range limits. Across our models, we find that phase structure and criticality are governed by the same effective-geometry principle, unifying our framework for experimentally motivated long-range
quantum systems.
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All authors Alex Gunning, Sebastian Schmid, Zhengxiao Liu, Sridevi Kuriyattil, Aydin Deger, Andrew J. Daley
Mesoscale and Nanoscale Physics
Simulating multi-node Weyl semimetals in a Mixed Floquet lattice
Goutham Vinjamuri, Ashutosh Dubey and Ankur Das
In this work, we simulate Weyl semimetal phases with multi-nodes containing 2, 4, 6, and 8 Weyl nodes, in a mixed Floquet synthetic
lattice generated by driving a one-dimensional chain with two incommensurate drives. In contrast to the integer-quantized response of Chern
insulators, we obtain a momentum-resolved power-transfer signature, where coupling the drives to fixed momenta results in quantized power-transfer for each 2D slice corresponding to that momentum, thereby locating the Weyl nodes in the low-frequency limit. Further, we explicitly show for the Weyl phase with 2 nodes, in the adiabatic limit, the half-filled state exchanges energy between the two drives at a rate that converges to the projected Weyl-node separation equal to the
Fermi-arc length of the Weyl semimetal.
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Mesoscale and Nanoscale Physics
Charge imprinting biases topology of correlated insulator in hBN-aligned rhombohedral multilayer graphene
Lei Qiao, Xin Lu, Fu-Chun Zhang et al. (+1 more)
Rhombohedral multilayer
graphene aligned with hexagonal boron nitride (RMG-hBN) hosts correlated Chern phases, but the microscopic role of hBN stacking remains unclear, especially when the active carriers are displaced away from the moiré interface. Using Hartree-Fock calculations over layer numbers, twist angles, displacement fields, fillings, and hBN
alignments, we show that correlated
insulators are most robust at small twist angles and intermediate layer number ($N\simeq 6$), where bandwidth suppression is balanced by layer delocalization of the wavefunctions of the active carriers. Under moiré-distant conditions at filling $\nu=1$, the
topology of the insulating state is strongly biased by charge imprinting: the hBN
alignment shapes the occupied valence-band charge texture near the interface via moiré potential, which acts through long-range Coulomb interactions as a remote electrostatic template for doped conduction electrons. Depending on the
alignment, this template favors either triangular charge localization associated with trivial
insulators or honeycomb-like charge networks compatible with Chern
insulators. Our results identify valence-band charge textures as a microscopic route by which a remote moiré interface controls correlated
topology in multilayer
graphene.
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All authors Lei Qiao, Xin Lu, Fu-Chun Zhang, Jianpeng Liu
Materials Science
Breaking symmetry to create a parallel-plate varactor dielectric with unparalleled microwave performance
Florian Bergmann, Matthew R. Barone, Zishen Tian et al. (+24 more)
Voltage-tunable capacitors (varactors) are key to microwave
circuits. Tunable dielectric varactors outperform competing technologies in almost every relevant metric but usually suffer from high dielectric loss. In contrast, Ruddlesden-Popper (RPs) dielectric thin films have remarkably low microwave loss. Unfortunately, their crystallographic
symmetry has until recently dictated an in-plane device structure, precluding the favorable out-of-plane parallel-plate varactor design for minimized size and maximized electric field in the tunable dielectric. Guided by theory, we report RPs akin to the widely studied tunable microwave dielectric BaxSr1-xTiO3. Assembling these same atoms into the first RP phase with broken out-of-plane
symmetry, we achieve a low-loss, out-of-plane tunable dielectric thin film. The highest performing film, (ATiO3)nAO film with A = Ba0.45Sr0.55 and n = 8, unlocks a tenfold improvement in the figure of merit for out-of-plane tunable dielectrics at 10 GHz, paving the way for a new generation of tunable monolithic microwave integrated
circuits.
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All authors Florian Bergmann, Matthew R. Barone, Zishen Tian, Aiden Ross, Gerhard H. Olsen, Meagan C. Papac, Samuel Freed, Bryan T. Bosworth, Nicholas R. Jungwirth, Eric J. Marksz, Tomasz Karpisz, Noah Schnitzer, Lopa Bhatt, David A. Muller, Dylan Sotir, Akash Surampalli, Veronica Goian, Christelle Kadlec, Stanislav Kamba, Asher Hansen, Nathan Rongitsch, Dmitri A. Tenne, Ichiro Takeuchi, Long-Qing Chen, Lane W. Martin, Nathan D. Orloff, Darrell G. Schlom
Mesoscale and Nanoscale Physics · Cross-listed from physics.app-ph
Determination of the intrinsic mechanical quality factor in high-stress silicon nitride resonators
Geena Benga, Vincent Dumont, Wei Wang et al. (+6 more)
Recent advances in silicon nitride nanomechanical resonators have pushed mechanical quality factors to ultra-high values by combining stress-induced dissipation dilution with mode-shape engineering. Neither mechanism alters the intrinsic quality factor $Q_{\mathrm{intr}}$. Targeting the intrinsic loss itself therefore remains an untapped route to even higher $Q$. Doing so first requires reliable quantification of $Q_{\mathrm{intr}}$, which has proven challenging. Here we present a robust methodology that quantifies $Q_{\mathrm{intr}}$ by combining automated mode identification with systematic ringdown measurements over a large number of mechanical modes. Applied to high-stress silicon nitride membranes, it reveals a systematic dependence of $Q_{\mathrm{intr}}$ on thickness that cannot be described using established models, particularly in the ultra-thin limit. We account for this trend with a phenomenological model that incorporates a thickness-dependent loss channel. Together, our method and model open a route toward a microscopic understanding of intrinsic dissipation and toward directly mitigating its loss channels.
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All authors Geena Benga, Vincent Dumont, Wei Wang, Nicola Cavalleri, Ariane Giesriegl, Silvan Schmid, Christian L. Degen, Antonius Armanious, Alexander Eichler
Materials Science
Effective masses, Burstein-Moss shift, and bandgap renormalization in degenerate Al-doped ZnO from broadband ellipsometry and Hall measurements
S. Mishra, L. A. Enrique, D. Cespedes et al. (+7 more)
A comprehensive methodology is developed to extract electron and hole effective masses in degenerate
semiconductors through a simultaneous global fit of carrier concentration dependence of bandgap and
plasma energy, explicitly incorporating band nonparabolicity. Broadband spectroscopic ellipsometry combined with
Hall effect analyses enables accurate determination of the bandgap,
plasma energy and carrier concentrations. The dielectric function of sputtered Al-doped ZnO thin films are modeled in the fundamental absorption region using an Elliott based model with overlapping excitonic transitions and Urbach tails, while free carrier absorption is described by a modified sernelius formula. Wide carrier concentrations are achieved via controlled deposition and post-annealing, revealing changes in electron effective masses and deviations from
parabolic dispersion. Two nonparabolic models are compared, Pisarkiewicz, assuming spherically symmetric band with a step-function approximation of the
Fermi-Dirac distribution and Nilsson, incorporating thermal and
impurity effects. The latter is shown to capture accurately band nonparabolicity, yielding effective masses and nonparabolicity parameter consistent with bandgap
evolution. This approach quantitatively separates Burstein-Moss shift and bandgap renormalization, reproducing carrier dependent bandgap shifts across a wide concentration range. Neglecting valence band contributions introduces systematic bias. Bandgap renormalization is further evaluated using plasmon pole and random phase approximations, underscoring the importance of many-body screening. This framework also enables determination of the Mott critical concentration and the fundamental absorption edge onset. Collectively, these results establish a reliable methodology for extracting band-structure parameters and bandgap shifts, extendable to other transparent conducting
oxides.
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All authors S. Mishra, L. A. Enrique, D. Cespedes, E. Perez, E. Serquen, F. Bravo, P. Llontop, F. Ruske, L. Korte, J. A. Guerra
Disordered Systems and Neural Networks · Cross-listed from cs.LG
Critical Percolation as a Synthetic Data Model for Interpretability
Aryeh Brill and Tom Ingebretsen Carlson
Neural networks learn features that reflect the hierarchical, multi-scale structure of natural data. Synthetic
datasets used to evaluate interpretability methods typically lack this structure, limiting their value as realistic toy models. To close this gap, we introduce a family of synthetic
datasets consisting of hierarchical functions defined on critical mean-field percolation clusters embedded in a high-dimensional data space. The percolation data consists of sparse, low-dimensional fractal clusters with a power-law size distribution. Latent variables modeling a taxonomic hierarchy generate each data point's target value. The data model is analytically tractable with known critical exponents that fix its properties without requiring hyperparameter tuning. We leverage a mapping between percolation clusters, random trees, and additive coalescence to propose an almost linear-time
algorithm to jointly sample a random tree and its hierarchical latent decomposition, enabling data generation at arbitrary scale. Using probing experiments, we find that the model's ground-truth latent variables can be linearly decoded from neural network activations. Together, sparsity, self-similarity, power-law statistics, and analytical tractability make critical percolation a principled testbed for interpretability research.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Phase locking nuclear spins in silicon with spin-orbit coupling
Habitamu Y. Walelign, Manas Ranjan Sahu and John M. Nichol
Because they have such long coherence times,
nuclear spins have extraordinary potential for use in
quantum information processing devices. However, coherent
nuclear spin control generally requires external phase references, such as microwave control fields. Here, we phase-lock a $^{29}$Si
nuclear spin ensemble in a silicon
quantum dot using only the internal electronic
spin-orbit coupling as a phase reference. When driven with the
quantum-dot electrons, the
nuclear spins align themselves to a phase determined by the electronic
spin-orbit coupling and the timing of the drive protocol. This enables us to measure the coherent precession and inhomogeneous dephasing of the
nuclear spins. We corroborate our results with detailed numerical simulations of the many-body electron
nuclear system. Our work opens new routes for coherently controlling solid-state
nuclear spin ensembles.
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Mesoscale and Nanoscale Physics
Diagnosing the origin of quantum oscillation beating in graphene
Akash Adhikary, Sunit Das, Divya Sahani et al. (+2 more)
Magnetic quantum oscillations are usually periodic in inverse
magnetic field, and their amplitude can show beating when two nearby frequencies interfere. In
graphene-based hexagonal systems, such beating can arise from strain-induced pseudomagnetic fields, unequal valley populations, valley-dependent energy shifts,
spin-orbit coupling-induced band splitting, or Kekulé distortions. Here, we show that the carrier density and
magnetic field dependence of the beating nodes can distinguish these mechanisms. Starting from Onsager's quantization relation, we derive scaling relations for the critical carrier density $N_c$ for the beating nodes as a function of critical
magnetic field $B_c$. A pseudomagnetic field gives $N_c\propto B_c^2$, whereas a density-independent valley imbalance gives $N_c\propto B_c$. A constant Dirac-band energy splitting by Zeeman-like
spin-orbit coupling also gives quadratic field scaling, but with a different node sequence: $N_{c,j}\propto(2j+1)B_{c,j}^2$ for a pseudomagnetic field and $N_{c,j}\propto(2j+1)^2B_{c,j}^2$ for energy splitting, where $j$ labels the beating node indices. These results provide quantitative constraints on different microscopic origins of valley- and
spin-dependent band splittings in
graphene-based systems.
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All authors Akash Adhikary, Sunit Das, Divya Sahani, Aveek Bid, Amit Agarwal
Materials Science
Tunable Flat Bands and magnetism in Triangulene-based Superatomic Graphene
Wenya Zhai, Tingfeng Zhang, Fengkun Chen et al. (+8 more)
Superatomic
graphene platforms host a rich portfolio of flat-band-driven exotic
quantum properties, yet their experimental realization remains challenging. Here, we report the bottom-up on-surface synthesis of superatomic
graphene using phosphorus-doped triangulene as building blocks. Scanning tunneling microscopy and spectroscopy measurements resolve the well-defined honeycomb
lattice of as-fabricated superatomic
graphene and demonstrate the characteristic Dirac band and flat band electronic structures. Density functional theory calculations reveal that the flat bands originate from the in-plane p$_x,_y$-like frontier orbitals of the phosphorus-doped triangulene units, leading to intrinsic half-metallic behavior. Furthermore, oxygen functionalization of the molecular precursor enables deterministic modulation of the electronic structure and
magnetic ordering. This work establishes a general platform for designing correlated
quantum materials with tunable flat band properties.
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All authors Wenya Zhai, Tingfeng Zhang, Fengkun Chen, Xiuqin Lu, Yunlong Xia, Zengfu Ou, Ye Chen, Donghui Guo, Meifang Zhu, Zhengfei Wang, Jingcheng Li
Superconductivity
Highly crystalline superconducting TiN resonators grown on thermally reconstructed sapphire
Thomas J. Smart, Marc Neis, Janine Lorenz et al. (+15 more)
High quality crystalline growth of a thin film on sapphire requires sufficient substrate preparation, often achieved via the use of aggressive chemical cleaning. Direct thermal reconstruction of the sapphire substrate via a CO$_2$
laser beam may allow for an alternative way to prepare the substrate for epitaxy without the use of any chemical processing. Within this work, we demonstrate that thermal annealing of sapphire into its ($\sqrt{31}$$\times$$\sqrt{31}$)$R$$\pm$9{\deg} reconstruction is a valid alternative preparation technique for sapphire substrates. TiN films grown via
plasma-assisted molecular beam epitaxy upon these substrates exhibit greater crystallinity than those grown on chemically cleaned sapphire substrates. Superconducting resonators fabricated from these films exhibit similar performance, with many possessing internal quality factors at single
photon levels greater than 10$^6$ for both substrate preparation methods.
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All authors Thomas J. Smart, Marc Neis, Janine Lorenz, Marcello P. Guardascione, Roudy Hanna, Michael Schleenvoigt, Yuan Gao, Joscha Domnick, Benjamin Bennemann, Abdur Rehman Jalil, Jin Hee Bae, Harsh Bhardwaj, F. Stefan Tautz, Felix Lüpke, Detlev Grützmacher, Rami Barends, Pavel A. Bushev, Peter Schüffelgen
Strongly Correlated Electrons
Fractional excitations in Kitaev quasi-one-dimensional chain
Ritwika Majumder
The Kitaev honeycomb model has attracted significant interest due to its
quantum spin liquid ground state, fractionalized Majorana excitations, and topological properties. Motivated by these features, we introduce a quasi-one-dimensional Kitaev-like
spin chain derived from a truncated honeycomb geometry. The resulting Majorana band structure contains both dispersive and flat bands, with a gap closing at a critical anisotropy that separates trivial and
chiral topological phases. Under open boundary conditions, the topological regime hosts zero-energy edge modes protected by
chiral symmetry, placing the system in the BDI
symmetry class with a quantized winding number. In the excited spectrum, localized plaquette modes emerge near zero energy and can be tuned by introducing domains of negative plaquettes. The dynamical
spin correlation function reveals broad continua associated with fractionalized excitations, together with characteristic low-energy spectral weight from edge Majorana modes. These features distinguish the present system from conventional Heisenberg
spin chains and provide experimentally relevant fingerprints of
chiral topological order. Our model thus establishes a conceptual bridge between the two-dimensional Kitaev
spin liquid and Kitaev's one-dimensional
quantum wire.
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Strongly Correlated Electrons
All-In-All-Out Pyrochlore Iridates as Noncollinear Spin-Orbit Coupled Counterparts of Altermagnets
Yang Yang, Turan Birol, Rafael M. Fernandes et al. (+1 more)
Altermagnets are collinear magnetically ordered states that exhibit momentum-dependent
spin splitting in the absence of net magnetization and
spin-orbit coupling (SOC). Related
spin-splitting patterns, however, can also emerge in noncollinear
magnetic systems with large SOC. Here we show, via a microscopic model, that the all-in-all-out (AIAO) state in pyrochlore iridates constitutes a noncollinear counterpart of a $d$-wave altermagnet stabilized by strong SOC. Starting from a microscopic $j_{\mathrm{eff}} = 1/2$ tight-binding model on the pyrochlore
lattice, we demonstrate that electronic interactions favor the AIAO phase and analyze its
symmetry properties. We show that the AIAO order parameter transforms as an $A_{2g}^{-}$ octupolar
magnetic moment, breaking time-reversal
symmetry while preserving inversion and zero net magnetization. Using group-theory analysis and mean-field calculations, we demonstrate that this
symmetry enforces both a
spin-polarized momentum-dependent lifting of band degeneracies that is similar to that of a collinear $d$-wave cubic altermagnet, but also a band splitting at zero-momentum. We show that the latter feature is captured by a low-energy model similar to the Luttinger-Kohn model for cubic
semiconductors. Our results identify pyrochlore iridates as a platform for noncollinear counterparts of altermagnetism and provide a general
symmetry framework for
spin-split phenomena in
spin-orbit coupled materials.
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All authors Yang Yang, Turan Birol, Rafael M. Fernandes, Natalia B. Perkins
Soft Condensed Matter
Multi-particle gates on driven one-dimensional paths: probing deep traps
Harsh Jain, Shankar Ghosh and Archishman Raju
We study single-file transport of driven overdamped colloidal particles on a periodic path with deep potential wells. In the small trap limit (i.e., trap size smaller than particle size), the particle current transitions from zero to finite as the number of particles on the path exceeds a critical number $n_c$. Beyond this threshold, $n_c$ particles cluster behind the trap, demonstrating collective correlated motion. The remaining `extra' particles circulate, giving a finite current. We study this phenomenon numerically using overdamped Brownian dynamics simulations, and present an experimental realization of this behaviour for micron-scale colloidal particles driven in an optical
vortex. Using our experimental observations, we present results characterizing potential wells as deep as several hundred $k_BT$.
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Quantum Gases
Arrival times of an atomic Bose-Einstein condensate
Pascal Naidon, Lucas Happ and Denis Boiron
The times of flight of an atomic Bose-Einstein condensate are theoretically investigated in the experimentally unexplored regime corresponding to detection close to the trap of the condensate. In this regime, there is no consensus on how to calculate the distribution of times of arrival onto the detector. For non-interacting particles, distinct theoretical predictions have been made in the past. This work analyses how these predictions are modified for an interacting Bose-Einstein condensate. For this purpose, a time-dependent Gross-Pitaevskii equation is solved analytically and numerically.
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Superconductivity
Spin transport in a normal meta-altermagnetic superconducting nanowire junction
Xing-Jian Yi, Yi-Xin Dai, Yue Mao et al. (+1 more)
Spin triplet
superconductors are considered a promising platform for dissipationless
spin transport, where
spin currents are carried by
spin triplet Cooper pairs. In this paper, we propose that the
spin triplet superconductivity and
spin supercurrent can be engineered in an altermagnetic superconducting nanowire, where a one-dimensional nanowire is placed on the surface of an s-wave
superconductor and in proximity to the altermagnet. Using the nonequilibrium Green's function method, we demonstrate a nonzero equal
spin Andreev reflection coefficient at the normal metal-altermagnetic superconducting nanowire interface, thereby verifying the injection of
spin triplet Cooper pairs. Furthermore, we systematically investigate the
spin transport properties in this hybrid system under a
spin bias. Our results demonstrate that these properties can be effectively tuned by the chemical potential and
spin bias orientation. Our proposal provides a pathway toward realizing dissipationless
spin transport.
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All authors Xing-Jian Yi, Yi-Xin Dai, Yue Mao, Qing-Feng Sun
Quantum Gases · Cross-listed from quant-ph
Proposal of quantum arrival-time measurement with a Bose-Einstein condensate
Pascal Naidon, Lucas Happ and Denis Boiron
This work shows how a Bose-Einstein condensate of ultracold atoms could be used to address a long-standing question in
quantum theory: how much time does it take for a particle to reach a detector? To this end, we propose a realistic experimental setup, whose key idea is not to measure arrival times directly, but the arrival flux on the detector as a function of its position. This novel approach not only solves practical issues with having a detector close to the system, but also results in signals that allow to unambiguously distinguish different theoretical predictions. This proposal raises prospects for resolving the decades-old debate on this fundamental issue.
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Materials Science
Exciton Transport in Disordered Perovskite Nanocrystal Solids
Simon Solari, Enrique Arévalo Rodríguez, Antonella Cutrupi et al. (+6 more)
Solution-processed thin films of colloidal lead halide perovskite (LHP) nanocrystals (NCs) show great potential for the implementation into optoelectronic devices such as light-emitting diodes (LEDs),
lasers, and
solar cells. However, these hybrid LHP NC solids exhibit non-negligible size and shape polydispersity, which introduces both structural and energetic disorder. Here, we resolve the
exciton dynamics in space, time, and energy to elucidate the impact of different forms of disorder (structural and energetic) on
exciton transport. We show that the disorder depends sensitively on the length of the alkylamine ligand used in the synthesis. While shorter alkyl chain lengths lead to high polydispersity, longer alkyl chains lead to more monodispersed and smaller particles where
quantum confinement becomes more pronounced and, consequently, lead to increased energetic disorder. Strikingly, we find that
exciton transport is less efficient in NC solids with long alkyl chain ligands, despite having a significantly more monodisperse ensemble. This demonstrates that energetic disorder, rather than structural disorder, is the dominant factor for predicting
exciton transport within these materials. These findings reveal the critical role of ligand engineering in designing high-performance optoelectronic devices based on hybrid LHP NCs, providing new insights into energy transport dynamics in disordered systems and highlighting the versatility of these materials for advanced photonic and optoelectronic applications.
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All authors Simon Solari, Enrique Arévalo Rodríguez, Antonella Cutrupi, Amalia Coro, Marc Meléndez, Alicia De Andrés, Almudena Torres-Pardo, Beatriz H. Juárez, Ferry Prins
Quantum Gases · Cross-listed from quant-ph
Interpreting Liouvillian Eigenmodes: Quantized Orbits in Dissipative Systems
Ashlin V Thomas, Felix Fritzsch, Masudul Haque et al. (+1 more)
In closed
quantum dynamics, energy eigenstates represent physical excitations which, for systems with a classical limit, localize on quantized orbits in phase space. Such a picture is lacking in open systems: Liouvillians have distinct right and left eigenstates that decay with time and are difficult to interpret. We recover a physical correspondence by introducing a gauge-invariant quasiprobability measure combining right and left eigenstates that interprets a Liouvillian mode as a set of coherences, allowing one to visualize the modes as quasiprobability distributions in a “doubled” phase space. Using this measure we show that, remarkably, a damped oscillator retains its quantized “orbits” for a large class of linear and nonlinear loss, with measurable signatures. A thermal bath broadens these orbits, similar to energy levels, leading to a characteristic multistage relaxation. This provides an experimentally accessible open-system analog of the eigenstate-orbit correspondence underlying semiclassical quantization. For quadratic systems, our results yield dissipative analogs of invariant
tori - a central concept in
Hamiltonian systems.
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All authors Ashlin V Thomas, Felix Fritzsch, Masudul Haque, Shovan Dutta
Strongly Correlated Electrons · Cross-listed from quant-ph
Vine Codes: Low-Overhead Quantum LDPC Codes on a Planar Square Grid
Georgia M. Nixon, Campbell K. McLauchlan and Charles C. L. van Rest
The surface code is a promising route towards large-scale
quantum computing, requiring only nearest-neighbour gates amenable to superconducting hardware. However, surface codes incur large
qubit overheads. Novel
quantum low-density parity check (qLDPC) codes promise to reduce overheads but require long-range connections that are difficult to achieve on superconducting platforms. Here, we introduce "Vine Codes" - qLDPC codes that are implementable on a planar square grid through nearest-neighbour, two-
qubit gates native to superconducting platforms (iSWAP and CZ). Our approach generalises "Directional Codes" recently introduced by Gehér et. al. (2025) which are constrained to a
torus. In contrast, vine codes have open boundary conditions constructed with the aid of routing
qubits. We perform extensive numeric searches and find promising candidate vine codes, e.g. [[121,4,6]], [[221,6,7]], and [[234,9,6]] codes. We verify the
circuit distances and show that data and measure
qubits required can be reduced by up to ~28% relative to the surface code at a
circuit distance of 7. Even including routing
qubits, vine codes require fewer total
qubits than the surface code (e.g. ~18% reduction at
circuit distance 10) and benefits are expected to increase at higher distances. We perform
circuit-level noise simulations to demonstrate that under a realistic noise model and at a near-term noise rate of $10^{-3}$, vine codes can perform better than the surface code while using fewer
qubits. We give an exhaustive list of all unique vine codes up to stabiliser-weight 9. We additionally introduce "Flip-Vine Codes" which possess single-
qubit transversal Clifford gates useful for fault-tolerant logic and magic state cultivation. We furthermore construct examples of generalised open boundaries for vine codes that go beyond the familiar X/Z boundaries of the surface and tile codes.
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Materials Science
Anomalous magneto-optical response at $\mathrm{RuO_2 / WSe_2}$ van der Waals interface
Muhammad Hassan Shaikh, Abhijith Puthiya Veettil, Collin Maurtua et al. (+9 more)
Ruthenium dioxide ($\mathrm{RuO_2}$) has been proposed as an altermagnetic candidate, although its
magnetic ground state remains controversial. Here, we probe weak interfacial
magnetic states at the surface of (001)-oriented $\mathrm{RuO_2}$ films using the
magnetic proximity effect (MPE) in a van der Waals
heterostructure consisting of monolayer tungsten diselenide ($\mathrm{WSe_2}$) atop $\mathrm{RuO_2}$. Temperature-dependent magneto-optical spectroscopy reveals an anomalous excitonic energy shift and a deviation from conventional Varshni behavior below 55 K that are absent in an encapsulated $\mathrm{WSe_2}$ control sample. The anomalous shift reverses sign upon field cooling with opposite
magnetic field polarity, indicating a
magnetic origin. Polarization-resolved measurements further show a nearly field-independent and fluctuating valley splitting in $\mathrm{WSe_2 / RuO_2}$ in strong contrast to the conventional linear Zeeman splitting observed in the control bare $\mathrm{WSe_2}$ sample. These results suggest that the valley states are governed predominantly by interfacial exchange fields associated with weak surface
magnetic states in $\mathrm{RuO_2}$, which do not produce a conventional linear Zeeman response within the applied
magnetic field range. Importantly, this approach enables direct optical probing of emergent surface magnetism without introducing an additional
ferromagnetic layer, positioning MPE-based optical probing as a tool for investigating weak surface magnetism and offering new possibilities for studying
magnetic materials with controversial
magnetic states.
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All authors Muhammad Hassan Shaikh, Abhijith Puthiya Veettil, Collin Maurtua, Dai Q. Ho, Subhash Bhatt, David T. Plouff, Malitha Gulawita, Kenji Watanabe, Takashi Taniguchi, John Q. Xiao, Anderson Janotti, Chitraleema Chakraborty
Soft Condensed Matter
Activity driven buckling and pattern formation in shells of oriented solids
Niels de Graaf Sousa, Varun Venkatesh and Amin Doostmohammadi
We investigate shells of active oriented solid, materials in which orientationally ordered active particles are embedded in a deformable elastic surface. Focusing on cylindrical geometries, we show that active stresses drive a new class of buckling instabilities and nonlinear patterns absent in passive shells. Linear stability analysis reveals that the unstable buckling mode is selected by the nematic orientation and activity sign, leading to axial, circumferential, and helical deformations. Remarkably, circumferential modes become unstable at arbitrarily small activity due to the absence of stretching costs. The results of the linear stability analysis are corroborated by full nonlinear simulations, which further uncover steady diamond shaped patterns and persistent dynamical states including oscillations, traveling domain walls, and propagating waves. Our results establish fundamental buckling modes and emergent patterns in shells of active oriented solid materials, with potential relevance to active biological tissues and engineered responsive materials.
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Strongly Correlated Electrons
Effects of nonlocal interactions on s- and d-wave superconducting correlations in the extended Hubbard model
Pavol Farkasovsky
We investigate the influence of nonlocal interactions on superconducting correlations within the extended Hubbard model. In addition to the on-site Coulomb interaction and nearest-neighbor hopping, we include next-nearest-neighbor hopping together with several physically relevant nonlocal terms, namely nearest-neighbor Coulomb interaction, correlated hopping, exchange interaction, and pair hopping. Using Lanczos exact diagonalization on a $4\times4$ cluster, supported by projector
quantum Monte Carlo simulations for selected parameter regimes, we analyze pairing correlations in both the s- and d-wave channels. We demonstrate that nonlocal interactions exert a highly nontrivial and
symmetry-dependent influence on superconducting correlations. While the on-site repulsion in cooperation with next-nearest-neighbor hopping enhances d-wave pairing tendencies, correlated hopping and nearest-neighbor Coulomb interaction strongly promote s-wave correlations, whereas exchange and pair-hopping interactions can efficiently suppress superconductivity beyond relatively small critical strengths. When all nonlocal interactions are considered simultaneously, the resulting phase diagrams reveal a complex interplay and competition between different pairing
symmetries. Our results highlight the crucial role of extended interactions in shaping the pairing landscape of strongly correlated systems and demonstrate that a comprehensive treatment beyond the minimal Hubbard model is essential for a realistic description of unconventional superconductivity.
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Superconductivity
Majorana modes in helical altermagnet without net magnetism and spin-orbit coupling
Xing-Jian Yi, Yue Mao, Cheng-Ming Miao et al. (+1 more)
We propose a scheme to realize topological
superconductor and Majorana bound states (MBSs) in a one-dimensional metal nanowire on the surface of a helical altermagnet and in proximity to an s-wave
superconductor, removing the requirement of conventional
spin-orbit coupling and net magnetism. Through gauge transformation, we demonstrate that the helical frame naturally induces
spin-momentum locking while the altermagnetism breaks time-reversal
symmetry. The topological superconducting phase is well tuned by chemical potential, altermagnet strength, and helical frequency. Besides, our transport calculation results reveal quantized conductance signatures: a 2e2/h zero-bias peak at nanowire ends and a 4e2/h tunneling conductance at the domain wall of nanowires with opposite chirality, detected via metal lead and scanning tunneling microscopy, respectively. Our research offers new perspectives on finding MBSs.
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All authors Xing-Jian Yi, Yue Mao, Cheng-Ming Miao, Qing-Feng Sun
Materials Science
On representation of macroscopic crack in periodic fine-scale discrete mechanical models
Jan Raisinger and Jan Eliáš
In multiscale modeling of heterogeneous softening materials, boundary conditions (BC) in the fine-scale model strongly influence the strain localization pattern and the macroscopic response. For rectilinear models (e.g., squares or cubes), standard Periodic BCs produce artificially ductile behavior with excessive energy dissipation when the localization band inclination does not match the periodicity directions. Recently proposed Tessellation and Percolation-path-aligned BCs promise to address this by adapting the periodicity frame to align with the evolving localization bands. Alternatively, spherical/circular models provide an orientation independent response by design. Unfortunately, the standard Periodic BCs do not allow development of proper localization band crossing spherical model's boundaries. A recently proposed modification addresses this by adding a displacement jump to the spherical periodic BCs. This study evaluates the applicability of these novel BCs to a mesoscale discrete particle model of concrete. Two-dimensional square and circular models under uniaxial tension with different loading directions are analyzed, with the selected approaches extended to three-dimensional cube models. Results show that Percolation-path-aligned BCs exhibit major shortcomings: they can lead to multiple localization bands due to uneven straining of the two boundary sections and their weakly constrained section can be prone to spurious strain localization. In contrast, Tessellation BCs consistently yield a well-defined localization band, whose length is determined solely by the model geometry, making it straightforward to account for in post-processing. Periodic boundary conditions augmented with a displacement jump applied to a circular model sometimes incorrect produce crack patterns similar to those under the standard Periodic BCs.
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Statistical Mechanics · Cross-listed from cs.AI
Thermodynamic Measure of Intelligence
Ishanu Chattopadhyay
Can intelligence be measured? We propose that intelligence can be defined as the lawful amplification of rare but valid futures: a system increases the probability of outcomes that would be unlikely under passive dynamics but remain admissible under the constraints of the domain. We start with the premise that an intelligent system must model the world and its own place within it. Because the system is part of the world it models, this leads naturally to recursive self-simulation: the system represents futures in which its own actions are part of the trajectory. Our central results give a necessity statement and a conditional near-sufficiency statement connecting this architecture to a precise thermodynamic measure of lawful amplification of rare-valid futures: high rare-valid lift is impossible unless the internal simulation identifies rare-valid futures with high fidelity; conversely, when rare-valid fidelity is high and the simulation contains an effective policy, the achievable lift approaches the actuation-limited optimum. Thus recursive self-simulation is not merely a plausible feature of intelligence but, under the stated assumptions, is necessary and nearly sufficient for high thermodynamic intelligence. The resulting framework makes intelligence measurable on a universal scale, from passive matter and feedback controllers, large
language models, and humans as text generators to Maxwell-demon-like information engines.
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Soft Condensed Matter
Independent Control of Transport and Order in a Ratcheted Colloidal Suspension
Sudipta Mandal, Dipanjan Chakraborty and Debasish Chaudhuri
We study directed transport in a two-dimensional suspension of repulsively interacting colloids driven by a
stochastic asymmetric piecewise-linear flashing ratchet using large-scale molecular dynamics simulations. The driving frequency and the ratchet asymmetry offer two independent ways of controlling the particle current, but they affect the suspension differently. At fixed asymmetry, the current shows a resonance with ratcheting frequency that is set by the collective relaxation dynamics of the interacting particles. The resulting increase in transport is accompanied by defect-mediated structural changes, showing density-dependent hexatic and solid-like states, with larger currents generally associated with weaker ordering. By contrast, at fixed frequency, changing the ratchet asymmetry mainly alters the strength of the directed bias and can significantly enhance the current while leaving the hexatic order largely unchanged. Near the
equilibrium hexatic-melting regime, this makes it possible to generate substantial directed currents without strongly disrupting sixfold orientational order. These results show that frequency tuning couples transport to structural reorganization, whereas asymmetry tuning primarily controls transport leaving the structure largely unaltered, providing distinct and complementary routes for manipulating transport and order in driven colloidal suspensions.
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Disordered Systems and Neural Networks
Truncated Wigner dynamics of biclique quantum spin glasses
Dries Sels
Quantum spin glasses are often considered testbeds for studying
quantum optimization
algorithms and as such have been the subject of various
quantum advantage claims. Here we investigate the near adiabatic dynamics of biclique
quantum spin glasses within the (discrete) truncated Wigner approximation (TWA).
Benchmarks on small systems show that TWA recovers sample-to-sample fluctuations of the Edwards-Anderson order parameter, over a wide range of annealing times, with increasing fidelity when the system size increases. We extract critical exponents from the Binder cumulant in line with theoretical expectations, reproducing recent
quantum experiments. The computational cost of the method is minimal and it can easily be applied to tens of thousands of
qubits.
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