Materials Science
Silicon Driven Facet Regulation Enables Tunable Micro-Diamond Architectures in Liquid Ga In
Zhi Jiang, Xueying Zhang, António José Silva Fernandes et al. (+2 more)
We report an ambient pressure
liquid metal assisted CVD strategy that enables shape programmable growth of micro scale diamond by coupling
liquid metl Ga In with ferrocene (Fe(C5H5)2) as an carbon precursor, nanodiamond seeds, and nanosilicon. Building on
liquid metal diamond synthesis, this approach pushes
liquid metal growth toward a low temperature (900 {\deg}C, 1 atm) while enabling single
crystal diamonds to be scaled from ~10 {\mu}m to several tens of micrometers with well developed faceting. Ferrocene decomposition supplies a sustained interfacial carbon flux that is captured and redistributed by the Ga In melt toward seed rich
liquid solid interfaces. Defect rich nanodiamond provides the crystallographic template required for reliable sp3 nucleation despite the intrinsically low carbon solubility of Ga In. Nanosilicon plays a distinct, complementary role by tuning interfacial kinetics and facet competition, enabling deliberate control of
crystal habit: cubic (~10 {\mu}m), truncated tetrahedral, and fully faceted octahedral diamonds are reproducibly obtained by adjusting the nanosilicon:nanodiamond ratio, with octahedral
crystals reaching ~50 {\mu}m. Importantly,
crystal size is further scaled by regulating hydrogen flow: lowering the H2 rate increases net carbon retention at the
liquid metal interface, raises effective supersaturation, and accelerates diamond deposition. Together, habit control (via nanosilicon: nanodiamond) and size scaling (via H2 flow) establish a practical route silicon driven facet regulation and size under ambient pressure, offering a pathway to tunable micro sized single
crystal diamonds under mild conditions.
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All authors Zhi Jiang, Xueying Zhang, António José Silva Fernandes, Marco Peres, Gil Gonçalves
Materials Science
Epitaxial Ni/Cu Superlattice Nanowires with Atomically Sharp Interfaces for Spin Transport
Janez Zavašnik, Sama Derakshan-Nejad, Maryam Ghaffari et al. (+6 more)
The importance of microstructure increases when decreasing the size of an object to the nanoscale, along with the complexity of controlling it. For instance, it is particularly complicated to create nano-object with controlled interfaces. Therefore, progressing towards 1D epitaxial nanostructures poses a challenge, and realization of their full potential is linked to technological issues of achieving large-scale, precise atom stacking of two or more different chemical elements. Achieving such coherent, epitaxial interfaces is a key step toward enabling spintronic phenomena in 1D objects, by minimizing interface scattering and strain-driven defects. Our results demonstrate a successful realization of controlled nanoscale heteroepitaxy in one-dimensional single-
crystal structures. We fabricated nanowires composed of alternating
magnetic (nickel) and non-
magnetic, highly conductive (copper) segments. This periodic stacking modulates electron transport under
magnetic stimuli. The epitaxial precision achieved eliminates detrimental electron scattering that has historically limited the magnetotransport properties of such 1D structures and hindered their development. Such materials are crucial for further advancements in the miniaturisation of nanosensors, actuators, and next-generation 3D spintronic devices.
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All authors Janez Zavašnik, Sama Derakshan-Nejad, Maryam Ghaffari, Amir Hassan Montazer, Mohammad Reza Mardaneh, Mohammad Almasi Kashi, Alexandre Nomine, Stephane Mangin, Uroš Cvelbar
Superconductivity
Microscopic structure of the vortex cores in granular niobium: A coherent quantum puzzle
V. S. Stolyarov, V. Neverov, A. V. Krasavin et al. (+12 more)
When macroscopic
quantum condensates –
superconductors, superfluids, cold atoms and ions, polaritons etc. – are put in rotation, a
quantum vortex lattice forms inside. In homogeneous type-II
superconductors, each
vortex has a tiny core where the superconducting gap $\Delta(r)$ is known to smoothly vanish towards the core centre on the scale of the coherence length $\xi$. The cores host quantized quasiparticle energy levels known as Caroli-de Gennes-Matricon (CdGM) bound states [Caroli et al., Phys. Lett. v. 9, 307 (1964)]. In pure materials, the spectrum of the low-lying CdGM states has the characteristic level spacing $\sim \Delta_0^2/E_F$, where $E_F$ is the
Fermi energy and $\Delta_0$ is the bulk gap. In disordered ones, the CdGM states shift and broaden due to scattering. Here, we show, both experimentally and theoretically, that the situation is completely different in granular Nb films, which are commonly used in superconducting electronics. In these films, in which the grains are smaller than $\xi$, the gap $\Delta$ in the quasiparticle spectrum reduces towards the
vortex core centres by discrete jumps at the grain boundaries. The bound states adapt to the local environment and appear at unexpectedly high energies. Both $\Delta(r)$ and bound states form a puzzle-like spatial structure of the core, elements of which are whole grains. Our discovery shakes up the established understanding of the
quantum vortex and encourages a reconsideration of the
vortex motion and pinning mechanisms in granular
superconductors.
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All authors V. S. Stolyarov, V. Neverov, A. V. Krasavin, D. I. Kasatonov, D. Panov, D. Baranov, O. V. Skryabina, A. S. Melnikov, A. A. Golubov, M. Yu. Kupriyanov, A. A Shanenko, T. Cren, A. Yu. Aladyshkin, A. Vagov, D. Roditchev
Soft Condensed Matter
Nonequilibrium noise emerging from broken detailed balance in active gels
Ashot Matevosyan, Frank Jülicher and Ricard Alert
In thermodynamic
equilibrium, the fluctuation-dissipation
theorem links thermal fluctuations and dissipation. Biological systems, however, are driven out of
equilibrium by internal processes that produce additional, active fluctuations. Despite being relevant for biological functions such as intracellular transport, predicting the statistical properties of active fluctuations remains challenging. Here, we address this challenge in a minimal model of an active gel as a network of elastic elements connected by transient crosslinks. The crosslinkers' binding and unbinding rates break detailed balance, which drives the system out of
equilibrium. Through coarse-graining, we derive fluctuating hydrodynamic equations including an active noise term, which emerges explicitly from the breaking of detailed balance. Finally, we provide predictions for the
stochastic motion of a tracer particle embedded in the active gel, which enables comparisons with microrheology experiments both in synthetic active gels and in
cells. Overall, our work provides an explicit link between the statistical properties of active fluctuations and the molecular breaking of detailed balance. Thus, it paves the way toward complementing the fluctuation-dissipation
theorem with a fluctuation-activity relation in active systems.
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Other Condensed Matter
Spin-orbit coupling and beyond in Chiral-Induced Spin Selectivity
Ruggero Sala, Sushant Kumar Behera, Abhirup Roy Karmakar et al. (+3 more)
Chiral-Induced
Spin Selectivity (CISS) describes the emergence of
spin-polarized electron transport in
chiral systems without
magnetic fields, a remarkable effect in light-element materials with weak intrinsic
spin-orbit coupling (SOC). This mini-review analyzes the microscopic origins of CISS, highlighting how molecular chirality, local electric fields, and dynamic distortions enhance effective SOC and drive
spin-dependent transport. We critically assess existing models in terms of their
symmetry constraints, phenomenological assumptions, and compliance with Onsager reciprocity. Recent developments combining relativistic
quantum mechanics and complete multipole representations reveal a direct link between chirality density and
spin current pseudoscalars, suggesting a field-theoretic foundation for CISS. These insights could help position light-element
chiral nanomaterials as tunable platforms for probing and engineering
spin-selective phenomena at the nanoscale.
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All authors Ruggero Sala, Sushant Kumar Behera, Abhirup Roy Karmakar, Matteo Moioli, Rocco Martinazzo, Matteo Cococcioni
Strongly Correlated Electrons
Critical Charge and Current Fluctuations across a Voltage-Driven Phase Transition
José F. B. Afonso, Stefan Kirchner and Pedro Ribeiro
We investigate bias-driven non-
equilibrium quantum phase transitions in a paradigmatic
quantum-transport setup: an interacting
quantum dot coupled to non-interacting metallic leads. Using the Random Phase Approximation, which is exact in the limit of a large number of dot levels, we map out the zero-temperature non-
equilibrium phase diagram as a function of interaction strength and applied bias. We focus our analysis on the behavior of the charge susceptibility and the current noise in the vicinity of the transition. Remarkably, despite the intrinsically non-
equilibrium nature of the steady state, critical charge fluctuations admit an effective-temperature description, $T_{\text{eff}}(T,V)$, that collapses the steady-state behavior onto its
equilibrium form. In sharp contrast, current fluctuations exhibit genuinely non-
equilibrium features: the fluctuation-dissipation ratio becomes negative in the ordered phase, corresponding to a negative effective temperature for the current degrees of freedom. These results establish current noise as a sensitive probe of critical fluctuations at non-
equilibrium quantum phase transitions and open new directions for exploring voltage-driven critical phenomena in
quantum transport systems.
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Materials Science
Topological-transition-driven Giant Enhancement of Second-harmonic Generation in Ferroelectric Bismuth Monolayer
Wen-Zheng Chen, Hongjun Xiang and Yusheng Hou
The interplay between band
topology and light in condensed materials could unlock intriguing nonlinear optical phenomena, enabling modern photonic technologies such as
quantum light sources and sub-wavelength topological
lasers. Here, we unveil that a buckling-tuned topological transition in ferroelectric bismuth monolayer unleashes a
giant second-harmonic generation. Using first-principles calculations, we surprisingly find that ferroelectric bismuth monolayer with a buckling parameter, $\Delta h$, has a large susceptibility $\chi^{(2)}$ on the order of $10^{7}$ $\mathrm{pm}^2/\mathrm{V}$, exceeding monolayer MoS$_2$ by about two orders of magnitude. When $\Delta h$ is engineered to the critical window where Dirac electrons emerge, a low-frequency resonance appears, boosting $\chi^{(2)}$ by an additional order of magnitude. We show that this enhancement is localized on the Dirac cones and dominated by intraband modification contributions. Based on an extended Dirac model, we establish that this enhancement physically originates from the ultralight effective masses $m^{*}$ of Dirac electrons through scaling with the
Fermi velocity $v_F$ and band gap $E_g$. Our findings provide a general paradigm for achieving exceptional second-harmonic generation via engineering topological criticality, and could serve as an experimental signature of Dirac electrons in topological materials.
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Disordered Systems and Neural Networks · Cross-listed from physics.soc-ph
Resilient-to-Fragile Transition and Excess Volatility in Supply Chain Networks
David Martin, José Moran, Debabrata Panja et al. (+1 more)
We study a production network in which firms use non-substitutable (Leontief) inputs, hold precautionary inventories and face idiosyncratic productivity shocks, with adjustment occurring through quantities rather than prices. We show analytically and numerically that a critical boundary exists in the space of shock
volatility and inventory holdings: above this threshold, the economy absorbs shocks and fluctuates mildly while below it, cascading shortages make system-wide crises inevitable. Close to the threshold, aggregate output
volatility diverges through network-mediated amplification of purely idiosyncratic shocks, providing a concrete mechanism for the “small shocks, large business cycles” puzzle. Because inventories are costly, competitive pressure drives firms toward the fragility boundary: a resilience-efficiency trade-off emerges, putting the gains from lean supply chains at risk. Finally, we show that supplier diversification shifts the threshold and, depending on its abundance, can eliminate the fragile regime entirely.
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All authors David Martin, José Moran, Debabrata Panja, Jean-Philippe Bouchaud
Materials Science
Contrasting impurity-induced magnetism and dynamics in 2H-MoTe2
Jonas A. Krieger, Igor P. Rusinov, Sourabh Barua et al. (+13 more)
We investigate the behavior of interstitial $^8$Li$^+$ implanted near the surface of 2H-MoTe$_2$ using $\beta$-detected NMR. We find that, unlike the
muon, $^8$Li$^+$ does not show any signature of induced magnetism. This result is consistent with density functional theory, which identifies the Li stopping site at the 2a Wyckoff position in the van der Waals gap and confirms the absence of detectable Li-induced electronic
spin polarization. Both the
spin-
lattice relaxation and the resonance lines show evidence of strong
spin dynamics above $\sim 200$ K, reminiscent of local
stochastic $^8$Li$^+$ motion within a cage. The resonance line shape consists of quadrupolar satellites on top of a broad central peak. To better understand the interaction of $^8$Li$^+$ with the host material, we employ a frequency-comb measurement, by simultaneously exciting four frequencies corresponding to the first-order quadrupolar satellite transitions, $\nu_0 \pm 3\nu_{\mathrm{comb}}$ and $\nu_0 \pm\nu_{\mathrm{comb}}$ around the Larmor frequency $\nu_0$ as a function of $\nu_{\mathrm{comb}}$. This offers an enhanced sensitivity to the quadrupolar split portion of the line. Using this method, we find a small decrease of the quadrupolar frequency with increasing temperature, showing the typical behavior associated with thermally excited
phonons and the absence of any
magnetic response which was observed with other defects in 2H-MoTe$_2$.
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All authors Jonas A. Krieger, Igor P. Rusinov, Sourabh Barua, Aris Chatzichristos, Jared Croese, Derek Fujimoto, Stefan Holenstein, Victoria L. Karner, Ryan M. L. McFadden, John O. Ticknor, W. Andrew MacFarlane, Robert F. Kiefl, Geetha Balakrishnan, Evgueni V. Chulkov, Stuart S. P. Parkin, Zaher Salman
Materials Science · Cross-listed from physics.chem-ph
SITH: A Quantum-Chemical Framework for Predicting Bond Destabilization in Stretched Molecules
Daniel Sucerquia, Mikaela Farrugia, Andreas Dreuw et al. (+1 more)
Mechanical forces can selectively destabilize chemical bonds of molecular systems, particularly in biological and synthetic
polymers. While experimental and theoretical methods have advanced our understanding of mechanochemical processes, predicting where energy concentrates within a molecule remains a significant challenge. To address this, we introduce SITH (Splitting Intramolecular Tension due to stretcHing), a novel method that decomposes the total electronic energy change of a stretched molecule into contributions from individual degrees of freedom – such as bond lengths, angles, and dihedrals – using numerical integration of the work-energy
theorem. Unlike previous approaches that rely on harmonic approximations, SITH provides high accuracy and robustness to study the distribution of energies of stretched molecules up to a first bond cleavage. Although SITH uses 3N-6 degrees of freedom for the energy decomposition, we show that it can work even for ring structures like prolines. We apply SITH to a
dataset of tripeptides and demonstrate that glycine and proline exhibit significantly different energy distributions in their Ca-C backbone bonds under tension: glycine stores more energy, making it more prone to rupture, while proline has the opposite behaviour. These findings reveal intrinsic differences in mechanochemical susceptibility across amino acids, offering more accurate predictions of bond rupture in
proteins, and similarly in other (bio)
polymers. SITH thus provides a powerful, interpretable tool for understanding energy distribution at the
quantum level, with possible implications in mechanochemistry and force field validation.
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All authors Daniel Sucerquia, Mikaela Farrugia, Andreas Dreuw, Frauke Gräter
Superconductivity
Giant anomalous Josephson effect as a probe of spin texture in topological insulators
Niklas Hüttner, Andreas Costa, Leandro Tosi et al. (+9 more)
Surface states of topological
insulators feature
chiral spin-momentum locking. When such states are used as weak link between two
superconductors, their
spin texture gives rise to the anomalous Josephson effect, i.e., to a $\varphi_0$ shift in the current phase relation. In this work, we explore the anomalous Josephson effect in junctions where the weak link is a HgTe nanowire. We observe a
giant anomalous $\varphi_0$-shift of the current-phase relation, which we attribute to the fact that HgTe surface states feature a single
Fermi contour. Moreover, by varying the orientation of the in-plane
magnetic field, we obtain information about the
spin texture in momentum space. In particular, we found that the
spin is not exactly perpendicular to the momentum, but shows a significant deviation of 19 degrees. Our results establish the anomalous Josephson effect as a sensitive tool to probe the
spin texture of
chiral 2D systems.
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All authors Niklas Hüttner, Andreas Costa, Leandro Tosi, Michael Barth, Wolfgang Himmler, Dmitriy A. Kozlov, Leonid Golub, Nikolay N. Mikhailov, Klaus Richter, Dieter Weiss, Christoph Strunk, Nicola Paradiso
Mesoscale and Nanoscale Physics
Mechanical sensing of metamagnetic tricriticality in two-dimensional CrI3
Feng Liu, Jiayong Xiao, Shengwei Jiang et al. (+2 more)
Layered Ising metamagnets are
antiferromagnetic (AF) materials consisting of monolayer Ising ferromagnets coupled to each other via interlayer AF interactions. They exhibit rich
magnetic phase diagrams, featuring tricritical and critical end points, due to the competing
magnetic interactions and the Ising anisotropy. While conventional thermodynamic probes can identify these critical points in bulk Ising metamagnets, achieving this in the two-dimensional (2D) limit, where enhanced fluctuation effects can substantially modify critical phenomena, remains to be realized. Here, we combine specific heat capacity (C_V) and
magnetic circular dichroism measurements to identify these critical points, extract a tricritical exponent, and map out the complete
magnetic phase diagram of 2D Ising metamagnetic CrI3. This is achieved in a nanomechanical device of 6-layer CrI3, in which a direct measurement of the temperature derivative of its mechanical resonance frequency gives C_V. The tricritical point is identified by the onset of an abrupt
spin-flip transition on one side and, on the other side, by a vanishing specific heat {\lambda}-anomaly for a continuous AF phase transition. In contrast, only the
spin-flip transition remains near the critical end point. Our results establish nanomechanical calorimetry as a general route to classify metamagnetic phase transitions and to study multicritical phenomena in 2D magnets.
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All authors Feng Liu, Jiayong Xiao, Shengwei Jiang, Kin Fai Mak, Jie Shan
Other Condensed Matter
Complex segregation patterns in confined nonuniform granular shearing flows
Santiago Caro, Riccardo Artoni, Patrick Richard et al. (+2 more)
When polydisperse granular systems are sheared, the transverse dynamics is characterized by the interplay of size segregation and
diffusion. Segregation in nonuniform and confined shearing flows is studied using annular shear
cell experiments complemented with discrete numerical simulations of bidisperse, inelastic, and frictional spheres under
gravity. We explored the role of shear localization, granular temperature, boundaries, and mixture properties in the
evolution of the segregation rate and the maximum degree of segregation achieved by a bidisperse granular system in the steady state. A faster segregation process and a more developed degree of segregation is observed for bidisperse mixtures with a larger size ratio and a higher proportion of large particles. Normally, in the presence of
gravity, size segregation induces large particles to rise and small particles to sink. However, two additional complex segregation patterns were found: inverse segregation and horizontal segregation. The first might be related to the kinematics of the flow, while the second is a geometrical effect. This additional segregation mechanism, in addition to
diffusion fluxes and high confining pressure, hampers complete segregation in the steady state, where some degree of mixing always persists.
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All authors Santiago Caro, Riccardo Artoni, Patrick Richard, Michele Larcher, James T. Jenkins
Mesoscale and Nanoscale Physics
Transit-time oscillations in nanoscale vacuum diode with a pure resistive load
Bjart{\th}hór Steinn Alexandersson, Kristinn Torfason, Andrei Manolescu et al. (+1 more)
We examine the Ramo current in a nanoscale planar
vacuum diode undergoing field emission in the presence of a DC voltage supply and an external resistor. We describe a simple mechanism for generating persistent current oscillations in the diode due to the voltage drop across the external resistor (beam loading) which reduces the total field and inhibits the emission. The amplitude and the frequency, which is in the THz domain, depend on the operating parameters of the diode. Molecular dynamics simulations are used to find the characteristics and physical basis of the mechanism, and a simple analytical model is presented, in good agreement with the simulation.
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All authors Bjart{\th}hór Steinn Alexandersson, Kristinn Torfason, Andrei Manolescu, Ágúst Valfells
Mesoscale and Nanoscale Physics
Coupled-wire descriptions of unconventional quantum states in twisted nanostructures
Chen-Hsuan Hsu and Anna Ohorodnyk
Coupled-wire description has been developed as a powerful framework for providing bosonic descriptions of strongly correlated
quantum matter, with early applications to systems such as the cuprates and the integer and fractional
quantum Hall states. In this topical review, we discuss recent developments of coupled-wire description in nanoscale systems, where it emerges not only as a theoretical tool but also as a highly tunable physical platform. In these nanoscale realizations, coupled-wire networks are formed by one-dimensional channels embedded in two-dimensional materials, most prominently in moiré and twisted structures. Such networks host a broad range of unconventional states of matter, including superconductivity, charge density waves,
spin density waves, Mott insulating phases, Anderson insulating phases,
quantum spin Hall states,
quantum anomalous
Hall states, and their fractionalized counterparts. The ability to electrically control interaction strength, confinement, and coupling between wires makes these systems qualitatively different from earlier realizations and allows continuous tuning between competing phases. Notably, recent work has demonstrated that the coupled-wire framework in moiré networks completes the trio of
quantum Hall phenomena, encompassing
quantum Hall,
quantum spin Hall, and
quantum anomalous
Hall states, together with their fractional analogues. This development highlights coupled-wire networks in nanoscale materials as a versatile and experimentally relevant setting for exploring the interplay of
topology, strong correlations, and low-dimensional physics.
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Strongly Correlated Electrons
Ground-State Phase Diagram of (1/2,1/2,1) Mixed Diamond Chains with Single-Site Anisotropy
Kazuo Hida
The ground-state phases of mixed diamond chains with ($S, \tau^{(1)}, \tau^{(2)})=(1/2,1/2,1)$, where $S$ is the magnitude of vertex
spins, and $\tau^{(1)}$ and $\tau^{(2)}$ are those of apical
spins, are investigated with the single-site anisotropy $D$ on the $\tau^{(2)}$-site. The two apical
spins in each unit
cell are coupled by an exchange coupling $\lambda$. The vertex
spins are coupled with the top and bottom apical
spins by exchange couplings $1+\delta$ and $1-\delta$, respectively. The ground-state phase diagram is determined using the numerical exact diagonalization and DMRG method in addition to the analytical approximations in various limiting cases. The phase diagram consists of a Néel ordered phase, a nonmagnetic Tomonaga-Luttinger
liquid phase, and quantized and partial ferrimagnetic phases. A region with anisotropy inversion is found where the Ising-like Néel phase is realized for the easy-plane anisotropy $D >0$ and the XY-like Tomonaga-Luttinger
liquid phase is realized for the easy-axis anisotropy $D <0$ on the $S=1$ sites.
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Materials Science
Tuning field amplitude to minimise heat-loss variability in magnetic hyperthermia
Necda Çam, Iago López-Vázquez, Òscar Iglesias et al. (+1 more)
In this work, we theoretically investigate how shape-induced anisotropy dispersion and
magnetic field amplitude jointly control both the magnitude and heterogeneity of heating in magnetite nanoparticle assemblies under AC
magnetic fields. Using real time Landau-Lifshitz-Gilbert simulations with thermal fluctuations, and a macrospin model that includes both the intrinsic cubic magnetocrystalline anisotropy and a shape-induced uniaxial contribution, we analyze shape-polydisperse systems under clinically and technologically relevant field conditions. We show that for relatively large particles, around 25 to 30 nm, the relative dispersion of local (single-particle) losses exhibits a well-defined minimum at moderate field amplitudes (between 4 to 12 mT), hence identifying an optimal operating regime that minimizes heating heterogeneity while maintaining substantial power dissipation. The position of this critical field depends mainly on particle size and excitation frequency, and only weakly on shape dispersion, offering practical guidelines for improving heating uniformity in realistic MFH systems.
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All authors Necda Çam, Iago López-Vázquez, Òscar Iglesias, David Serantes
Superconductivity
Low-temperature anomaly and anisotropy of critical magnetic fields in transition-metal dichalcogenide superconductors
Tomoya Sano, Kota Tabata, Akihiro Sasaki et al. (+1 more)
We clarify why
spin-singlet superconductivity persists in monolayer transition-metal dichalcogenides even in high
magnetic fields beyond the Pauli limit. The phenomenon called Ising protection is caused by two magnetically active potentials: a Zeeman field and an Ising
spin-orbit interaction. These potentials induce two
spin-triplet pairing correlations in a
spin-singlet
superconductor. One belonging to odd-frequency
symmetry class arises solely from a Zeeman field and always makes the superconducting state unstable. The other belonging to even-frequency
symmetry class arises from the interaction between the two
magnetic potentials and eliminates the instability caused by odd-frequency pairs. The presence or absence of such even-frequency
spin-triplet pairs explains the anisotropy of the Ising protection. The analytical expression of the superfluid weight enables us to conclude that induced even-frequency
spin-triplet Cooper pairs support
spin-singlet superconductivity in high Zeeman fields.
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All authors Tomoya Sano, Kota Tabata, Akihiro Sasaki, Yasuhiro Asano
Other Condensed Matter · Cross-listed from quant-ph
Fingerprints of classical memory in quantum hysteresis
Francesco Caravelli
We present a simple framework for classical and
quantum “
memory” in which the
Hamiltonian at time $t$ depends on past values of a control
Hamiltonian through a causal kernel. This structure naturally describes finite-bandwidth or filtered control channels and provides a clean way to distinguish between
memory in the control and genuine non-Markovian dynamics of the state. We focus on models where $H(t)=H_0+\int_{-\infty}^{t}K(t-s)\,H_1(s)\,ds$, and illustrate the framework on single-
qubit examples such as $H(t)=\sigma_z+\Phi(t)\sigma_x$ with $\Phi(t)=\int_{-\infty}^{t}K(t-s)\,u(s)\,ds$. We derive basic properties of such dynamics, discuss conditions for unitarity, give an equivalent time-local description for exponential kernels, and show explicitly how hysteresis arises in the response of a driven
qubit.
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Strongly Correlated Electrons
Microscopic Determination of the c-axis-Oriented Antiferromagnetic Structure in LaMnSi by $^{55}$Mn and $^{139}$La NMR
Yusuke Sakai, Fumiya Hori, Hiroki Matsumura et al. (+4 more)
We report a microscopic investigation of the
magnetic structure and electronic properties of LaMnSi in its
antiferromagnetic (AFM) state using
nuclear magnetic resonance (NMR). Field-swept $^{55}$Mn- and $^{139}$La-NMR spectra, as well as zero-field 55Mn-NMR (ZFNMR) spectra, reveal that the Mn ordered moments are parallel to the tetragonal c axis, consistent with the C-type AFM structure and the realization of an odd-parity multipole order. The internal field at the Mn site is determined to be 19.64 T at 4.2 K, corresponding to a hyperfine coupling constant of Ahf = 6.0 T/uB.
Nuclear spin-
lattice relaxation rate 1/T1 exhibits a characteristic behavior of itinerant antiferromagnetism, showing metallic behavior at low temperatures and
magnon-induced enhancement upon approaching the Neel temperature (TN = 295 K). These results show LaMnSi as an ideal compound to study 3d electron magnetism and odd-parity multipole order in the RT Si (R = rare-earth, T = transition metal) system, free of the complexities of 4f electrons.
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All authors Yusuke Sakai, Fumiya Hori, Hiroki Matsumura, Shumpei Oguchi, Shunsaku Kitagawa, Kenji Ishida, Hiroshi Tanida
Materials Science
ALD-Derived WO3-x Leads to Nearly Wake-Up-Free Ferroelectric Hf0.5Zr0.5O2 at Elevated Temperatures
Nashrah Afroze, Jihoon Choi, Salma Soliman et al. (+10 more)
Breaking the
memory wall in advanced computing architectures will require complex 3D integration of emerging
memory materials such as ferroelectrics-either within the back-end-of-line (BEOL) of CMOS front-end processes or through advanced 3D packaging technologies. Achieving this integration demands that
memory materials exhibit high thermal resilience, with the capability to operate reliably at elevated temperatures such as 125C, due to the substantial heat generated by front-end transistors. However, silicon-compatible HfO2-based ferroelectrics tend to exhibit antiferroelectric-like behavior in this temperature range, accompanied by a more pronounced wake-up effect, posing significant challenges to their thermal reliability. Here, we report that by introducing a thin tungsten
oxide (WO3-x) layer-known as an oxygen reservoir-and carefully tuning its oxygen content, ultra-thin Hf0.5Zr0.5O2 (5 nm) films can be made robust against the ferroelectric-to-antiferroelectric transition at elevated temperatures. This approach not only minimizes polarization loss in the pristine state but also effectively suppresses the wake-up effect, reducing the required wake-up cycles from 105 to only 10 at 125C- a qualifying temperature for back-end
memory integrated with front-end logic, as defined by the JEDEC standard. First-principles density functional theory calculations reveal that WO3 enhances the stability of the ferroelectric orthorhombic phase at elevated temperatures by increasing the tetragonal-to-orthorhombic phase energy gap, and promoting favorable
phonon mode
evolution, thereby supporting o-phase formation under both thermodynamic and kinetic constraints.
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All authors Nashrah Afroze, Jihoon Choi, Salma Soliman, Chang Hoon Kim, Jiayi Chen, Yu-Hsin Kuo, Mengkun Tian, Chengyang Zhang, Priyankka Gundlapudi Ravikumar, Suman Datta, Andrea Padovani, Jun Hee Lee, Asif Khan
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Soft X-ray Reflection Ptychography
Damian Guenzing, Dayne Y. Sasaki, Alexander S. Ditter et al. (+9 more)
Scanning transmission X-ray microscopy and ptychography have become mature tools for high-resolution, element-specific imaging of nanoscale structures. However, transmission geometries impose stringent constraints on sample thickness and preparation, thereby limiting investigations of extended or bulk specimens, especially in the soft X-ray region. Here, we demonstrate reflection geometry soft X-ray ptychography as a robust imaging mode. Instrumental feasibility and spatial resolution are established using a lithographically defined Siemens
star and barcode test pattern on a multilayer substrate. We empirically demonstrate a full-pitch spatial resolution of ca. 45 nm from
Fourier ring correlation analysis of the reconstructed object. The results highlight the potential of the reflection geometry for nondestructive X-ray studies of materials without the need for transmissive samples.
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All authors Damian Guenzing, Dayne Y. Sasaki, Alexander S. Ditter, Abraham L. Levitan, Eric M. Gullikson, Scott Dhuey, Arian Gashi, Hendrik Ohldag, Sujoy Roy, David A. Shapiro, Riccardo Comin, Sophie A. Morley
Mesoscale and Nanoscale Physics
Quantum capacitance and parity switching of a quantum-dot-based Kitaev chain
Chun-Xiao Liu
An array of
quantum dots coupled via superconductivity provides a new platform for creating Kitaev chains with Majorana zero modes, offering a promising avenue toward topological
quantum computing. In this work, we theoretically study the
quantum capacitance of a minimal Kitaev chain weakly coupled to an external normal lead. We find that in the open regime, charge stability diagrams of
quantum capcaitance can help to identify the sweet spot of a Kitaev chain, consistent with tunnel spectroscopy. Moreover, the
quantum capacitance of a single
quantum dot coupled to Andreev bound states reveals the interplay between two distinct parity switching mechanisms: coupling to an external normal lead and intrinsic quasiparticle poisoning. Our work provides useful physical insights into the
quantum capacitance and parity dynamics in a
quantum-dot-based Kitaev chain device.
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Materials Science
Vibrational and Electronic Properties of Np2O5 from Experimental Spectroscopy and First Principles Calculations
Binod K Rai, Shuxiang Zhou, Benjamin R. Heiner et al. (+7 more)
High-valence actinide
oxides are critical to understanding the behavior of 5f-electrons, yet their structural and electronic properties remain poorly understood due to challenges in synthesis and handling. We report the first Raman spectroscopic study of single-crystalline Np2O5 and the first scanning tunneling spectroscopy (STS) measurement on any neptunium-containing material. Hydrothermally synthesized
crystals were structurally verified by X-ray diffraction. Raman spectra revealed sharply resolved vibrational features, including previously unreported low-frequency modes. STS measurements revealed a band gap of 1.5 eV. Density functional theory (DFT) enables vibrational mode assignments, reveals neptunium-dominated low-frequency
phonons, oxygen-dominated high-frequency modes, and predicts an indirect band gap of 1.68 eV. This predicted value is in excellent agreement with the experimentally measured STS gap. This combined Raman, DFT, and STS approach provides a robust framework for correlating
lattice dynamics and electronic structure in actinide materials, providing
benchmark data for Np2O5, and opening new avenues for probing structure-property relationships in complex f-electron materials.
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All authors Binod K Rai, Shuxiang Zhou, Benjamin R. Heiner, Gia Thinh Tran, Jennifer E. S. Szymanowski, Santosh KC, Thomas C. Shehee, Peter C. Burns, Miles F. Beaux II, Luke R Sadergaski
Statistical Mechanics · Cross-listed from physics.chem-ph
Quantum statistics from classical simulations via generative Gibbs sampling
Weizhou Wang, Xuanxi Zhang, Jonathan Weare et al. (+1 more)
Accurate simulation of
nuclear quantum effects is essential for molecular modeling but expensive using path integral molecular dynamics (PIMD). We present GG-PI, a ring-
polymer-based framework that combines generative modeling of the single-bead conditional density with Gibbs sampling to recover
quantum statistics from classical simulation data. GG-PI uses inexpensive standard classical simulations or existing data for training and allows transfer across temperatures without retraining. On standard test systems, GG-PI significantly reduces wall clock time compared to PIMD. Our approach extends easily to a wide range of problems with similar Markov structure.
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All authors Weizhou Wang, Xuanxi Zhang, Jonathan Weare, Aaron R. Dinner
Soft Condensed Matter
Steering Active-Colloid Assembly by Biasing Dissipation
Chaoqun Du, Zhiyu Cao and Zhonghuai Hou
Complex nonequilibrium self-assembly enables the formation of materials with specific patterns and functions from the bottom up. How to directionally control the assembly to form the target configuration is a challenge. Here, we propose a dissipation bias principle for targeted assembly, which highlights that controlling the dissipation tendency can play an important role by modulating the frequency and intensity of local rearrangements. Following this principle, one can induce ordered target configurations from disordered structures and also achieve directional selection among multiple assembly pathways. We use the assembly of active colloids as a platform to show our results.
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Strongly Correlated Electrons
High-precision ground state parameters of the two-dimensional spin-1/2 Heisenberg model on the square lattice
Anders W. Sandvik
Several ground state properties of the square-
lattice $S=1/2$ Heisenberg antiferromagnet are computed (the energy, order parameter,
spin stiffness, spinwave velocity, long-wavelength susceptibility, and staggered susceptibility) using extensive
quantum Monte Carlo simulations with the
stochastic series expansion method. Moderately sized
lattices are studied at temperatures $T$ sufficiently low to realize the $T \to 0$ limit. Results for periodic $L\times L$
lattices with $L \in [6,96]$ are tabulated versus $L$ and extrapolations to infinite system size are carried out. The extrapolated ground state energy density is $e_0=-0.669441857(7)$, which represents an improvement in precision of three orders of magnitude over the previously best result. The leading and subleading finite-size corrections to $e_0$ are in full quantitative agreement with predictions from
chiral perturbation theory, thus further supporting the soundness of both the extrapolations and the theory. The extrapolated sublattice magnetization is $m_s=0.307447(2)$, which agrees well with previous estimates but with a much smaller statistical error. The coefficient of the linear in $L^{-1}$ correction to $m^2_s$ agrees with the value from
chiral perturbation theory and the presence of a factor $\ln^\gamma(L)$ in the second-order correction is also confirmed, with the previously not known value of the exponent being $\gamma = 0.82(4)$. The finite-size corrections to the staggered susceptibility point to logarithmic corrections also in this quantity. To facilitate benchmarking of methods for which periodic boundary conditions are challenging, results for systems with open and cylindrical boundaries are also listed and their spatially inhomogeneous order parameters are analyzed.
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Statistical Mechanics
Complex nonlinear sigma model
Kazuki Yamamoto and Kohei Kawabata
Motivated by the recent interest in the criticality of open
quantum many-body systems, we study nonlinear sigma models with complexified couplings as a general framework for nonunitary field theory. Applying the perturbative renormalization-group analysis to the tenfold symmetric spaces, we demonstrate that fixed points with complex scaling dimensions and critical exponents arise generically, without counterparts in conventional nonlinear sigma models with real couplings. We further clarify the global phase diagrams in the complex-coupling plane and identify both continuous and discontinuous phase transitions. Our work thus identifies nonlinear sigma models as a representative setting for studying complex critical points and elucidates universal aspects of critical phenomena in complexified field theory.
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Soft Condensed Matter
Tunable Nanoparticle Stripe Patterns at Inclined Surfaces
Suman Bhattacharjee, Sanjoy Khawas and Sunita Srivastava
Periodic assemblies of nanoparticles are central to surface patterning, with applications in biosensing, energy conversion, and nanofabrication. Evaporation of colloidal droplets on substrates provides a simple yet effective route to achieve such assemblies. This work reports the first experimental demonstration of patterns formed through stick-slip dynamics of the three-phase contact line during evaporation of gold nanoparticle suspensions on inclined substrates. Variation in nanoparticle concentration and substrate inclination alter the balance of interfacial and gravitational forces, producing multiple stick-slip events that generate periodic stripes. Stripe density exhibits a sinusoidal dependence on inclination angle, while inter-stripe spacing remains nearly invariant. Independent control over inter-stripe spacing is achieved through adjustment of nanoparticle or surfactant concentration. These results highlight the complex interplay of gravitational and interfacial forces in directing periodic nanoparticle assembly and establish a versatile, programmable framework for surface patterning with tunable nano/microscale dimensions.
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