Mesoscale and Nanoscale Physics
Perturbative sensing of nanoscale materials with millimeter-wave photonic crystals
Kevin K. S. Multani, Zhurun Ji, Wentao Jiang et al. (+7 more)
We introduce millimeter-wave silicon photonic
crystal cavities as a versatile platform for the perturbative sensing of nanoscale materials. This dielectric-based platform is compatible with strong
magnetic fields, opening avenues for studying
quantum materials in extreme environments where superconducting cavities cannot operate. To establish the platform's performance, we cryogenically characterize a silicon photonic
crystal cavity at 4.3 K, achieving a total quality factor exceeding $10^5$ for a 96 GHz mode. As a proof-of-concept for its sensing capabilities, we position a hexagonal boron nitride-multilayer
graphene (hBN-MLG)
heterostructure at an electric-field antinode of the cavity and measure the perturbative response at room temperature. The
heterostructure induces a significant change in the cavity's resonance, from which we extract a total sample conductivity of approximately $5.1\times10^6$~S/m. These results establish silicon photonic
crystal cavities as a promising platform for sensitive, on-chip spectroscopy of nanoscale materials at millimeter-wave frequencies.
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All authors Kevin K. S. Multani, Zhurun Ji, Wentao Jiang, Siyuan Qi, Akasha G. Hayden, Gitanjali Multani, Sharon Ruth S. Platt, Emilio A. Nanni, Zhi-Xun Shen, Amir H. Safavi-Naeini
Soft Condensed Matter
Tracking the Brownian motion of DNA-functionalized magnetic nanoparticles for conformation analysis beyond the optical resolution limit
Christian Janzen, Fabian Schmid-Michels, Yahya Shubbak et al. (+6 more)
Brownian motion provides access to hydrodynamic properties of nanoscale objects independent of their optical resolvability. Here, we present a
diffusion-based approach to infer effective particle size distributions of DNA-functionalized
magnetic nanoparticles (MNPs), consisting of a
magnetic core and a polystyrene shell, in a regime where direct
geometric sizing is limited by optical diffraction. Using multi-particle tracking microscopy, we analyze the Brownian dynamics of MNPs grafted with double-stranded DNA (dsDNA) of varying contour length under low-salt conditions. A physically motivated model is introduced that relates dsDNA contour length to an effective hydrodynamic diameter via an attenuated corona description. The measured
diffusion coefficient distributions exhibit a systematic and monotonic dependence on dsDNA length in quantitative agreement with the model. While the tracked objects are predominantly dsDNA-mediated agglomerates rather than isolated nanoparticles, clustering does not obscure the length-dependent signal. Instead, the dsDNA corona determines the hydrodynamic scaling, whereas agglomeration mainly introduces an offset and distribution broadening. These results demonstrate that Brownian dynamics enables robust readout of biomolecular length scales even far below the optical resolution limit. The distribution-based approach is inherently tolerant to polydispersity and aggregation, making
diffusion-based tracking a simple and promising strategy for future biotechnological and biomedical assays.
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All authors Christian Janzen, Fabian Schmid-Michels, Yahya Shubbak, Melanie Wegener, Karl-Josef Dietz, Inga Ennen, Rico Huhnstock, Arno Ehresmann, Andreas Hütten
Mesoscale and Nanoscale Physics
Prediction of two-dimensional $\pi$-electron half-metallic ferrimagnets
J. Phillips, J. C. G. Henriques, J. Fernández-Rossier et al. (+1 more)
We propose a strategy to obtain conducting organic materials with fully
spin-polarized
Fermi surface, lying at a singular flat band, with antiferromagnetically coupled
magnetic moments that reside in pi-orbitals of nanographenes. We consider a honeycomb
crystal whose unit
cell combines two different molecules with $S=1/2$: an Aza-3-Triangulene, a molecule with orbital degeneracy, and a 2-Triangulene. The analyzed system is half-metallic with a ferrimagnetic order, presenting a zero net total
magnetic moment per unit
cell. We combine density functional theory calculations with a Hubbard model
Hamiltonian to compute the
magnetic interactions, the bands, the intrinsic Anomalous
Hall effect, and the collective
spin excitations. We obtain very large intermolecular exchange couplings, in the range of 59 meV. Based on the
spin excitation dispersion, we estimate thermal stability in the range of 100 Kelvin. When the magnetization is off-plane, intrinsic
spin orbit coupling in
graphene opens up a topological gap that, despite being very small, leads to a quantized
Hall conductance in the tens of mK range, but is thermally smeared above 1 Kelvin.
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All authors J. Phillips, J. C. G. Henriques, J. Fernández-Rossier, A. T. Costa
Materials Science
Multi-Method Li Plating Characterization of a Commercial 26 Ah Li-Ion Pouch-Cell
Christiane Rahe, Heinrich Ditler, Thorsten Tegetmeyer-Kleine et al. (+21 more)
Lithium (Li) plating on graphite is a significant degradation mechanism in Li-ion batteries. While numerous experimental techniques have been used to study Li plating in laboratory
cells, investigations of commercial high-energy
cells often rely on electrochemical methods. Here we present and classify various methods for detecting Li plating on a commercial A123 pouch
cell. In a round robin study across multiple battery research laboratories, Li-plated graphitic electrode material was analyzed using electrochemical, microscopic, and spectroscopic methods capable of detecting metallic Li deposits. After
cell opening, their overall distribution on the anode surface was examined using a flatbed scanner to ensure comparability of the samples. Optical and electron microscopy provided detailed surface and, in combination with a focused ion beam, subsurface structure and morphology. Spectroscopic methods confirmed the presence and onset of plated Li with varying sensitivity. Moreover, spectroscopic and imaging techniques were combined correlatively where possible. Availability and measurement duration of each technique was compared. Optical methods are fast and easy to use; thus, they are recommended for most samples, with spectroscopic confirmation reserved for reference samples. This
multimodal study demonstrates a range of methods that can be used alone or in combination to qualitatively or quantitatively detect Li-plating.
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All authors Christiane Rahe, Heinrich Ditler, Thorsten Tegetmeyer-Kleine, Marius Flügel, Thomas Waldmann, Margret Wohlfahrt Mehrens, Philipp Schleker, Peter Jakes, Beatrice Wolff, Josef Granwehr, Rüdiger-A. Eichel, Jiří Vacík, Giovanni Ceccio, Antonino Cannavo, Ivana Pivarníková, Ralph Gilles, Peter Müller-Buschbaum, Adrian Mikitisin, Joachim Mayer, Michael Noyong, Ulrich Simon, Marius Bolsinger, Volker Knoblauch, Dirk Uwe Sauer
Mesoscale and Nanoscale Physics
Charge and energy transport in graphene with smooth finite-range disorder
Juan A. Cañas, Daniel A. Bonilla, J. C. Pérez-Pedraza et al. (+1 more)
We investigate charge and energy transport in monolayer
graphene with smooth finite-range disorder, modeled by soft
impurity potentials. Using a continuum Dirac model, we go beyond the Born approximation by computing the exact scattering
matrix for individual
impurities. This captures the full nonperturbative physics of smooth disorder. From the exact scattering data, we evaluate transport coefficients by solving the Boltzmann equation with energy-resolved phase shifts. We analyze electrical and electronic thermal conductivities versus carrier density and temperature, including deviations from the Wiedemann-Franz law. Our results reveal that finite-range disorder nontrivially modifies charge and heat currents, especially at low energies where perturbative methods fail. These findings provide a more accurate transport characterization for disordered Dirac materials and clarify how smooth disorder governs energy flow in
graphene.
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All authors Juan A. Cañas, Daniel A. Bonilla, J. C. Pérez-Pedraza, A. Martín-Ruiz
Statistical Mechanics
Matrix-product operator dualities in integrable lattice models
Yuan Miao, Andras Molnar and Nick G. Jones
Matrix-product operators (MPOs) appear throughout the study of integrable
lattice models, notably as the transfer
matrices. They can also be used as transformations to construct dualities between such models, both invertible (including
unitary) and non-invertible (including discrete gauging). We analyse how the local Yang–Baxter integrable structures are modified under such dualities. We see that the $\check{R}$-
matrix, that appears in the baxterization approach to integrability, transforms in a simple manner. We further argue for a broad class of MPO dualities that the usual Yang–Baxter $R$-
matrix should be extended. This extended $R$-
matrix satisfies modified algebraic relations, including a modified Yang–Baxter
algebra previously identified in the
unitary case, that altogether give a local integrable structure underlying the commuting transfer
matrices of the dual model. We illustrate these results with two case studies, analysing an invertible
unitary MPO and a non-invertible MPO both applied to the canonical XXZ
spin chain. The former is the cluster entangler, arising in the study of
symmetry-protected topological phases, while the latter is the Kramers–Wannier duality. We show several results for MPOs with exact MPO inverses that are of independent interest.
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Quantum Gases
Mott-insulating phases of the Bose-Hubbard model on quasi-1D ladder lattices
Lorenzo Carfora, Callum W. Duncan, Stefan Kuhr et al. (+1 more)
We calculate the phase diagram of the Bose-Hubbard model on a half-filled ladder
lattice including the effect of finite on-site interactions. This shows that the rung-Mott
insulator (RMI) phase persists to finite interaction strength, and we calculate the RMI-superfluid phase boundary in the thermodynamic limit. We show that the phases can still be distinguished using the number and parity variances, which are observables accessible in a
quantum-gas microscope. Phases analogous to the RMI were found to exist in other quasi-1D
lattice structures, with the
lattice connectivity modifying the phase boundaries. This shows that the the presence of these phases is the result of states with one-dimensional structures being mapped onto higher dimensional systems, driven by the reduction of hopping rates along different directions.
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All authors Lorenzo Carfora, Callum W. Duncan, Stefan Kuhr, Peter Kirton
Quantum Gases
Hartree shift and pairing gap in ultracold Fermi gases in the framework of low-momentum interactions
Michael Urban and S. Ramanan
In this paper we consider a two-component gas of
fermions on the BCS side of the BCS-BEC crossover at zero temperature. We use a momentum dependent interaction that reproduces the s-wave scattering phase shifts of a contact interaction up to a momentum cutoff that is scaled with the
Fermi momentum. Using a diagrammatic formulation of Bogoliubov many-body perturbation theory, suitably augmented by self-consistency conditions, we obtain the Hartree shift and the pairing gap to third order. In the weak-coupling regime, our results are not only well-converged but also agree with the well-established Gor'kov-Melik-Barkhudarov corrections for the gap and the Galitskii result for the Hartree shift. Near the
unitary regime, our results for the Nambu-Gor'kov self-energy are less converged, but there is still reasonable agreement with experiments as well as with
quantum Monte-Carlo results. Perspectives for improvements and applications of this approach to
neutron matter are discussed.
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Superconductivity
Frederik A. S. Philipsen, Mats Barkman, Andreas Kreisel et al. (+1 more)
We perform a theoretical investigation of the nature of
vortices in
chiral $d+id$
superconductors on the kagome
lattice. The study is motivated by recent experimental developments reporting evidence of time-reversal
symmetry breaking in the superconducting state of kagome metals. Using self-consistent microscopic calculations that incorporate the characteristics of the band structure of the kagome
lattice, we find that fractional
vortices permeate the ground state condensate in the presence of an external field. Each fractional
vortex carries one third of the superconducting flux
quantum and exhibits a characteristic signature related to one of the three sublattice degrees of freedom of the kagome
lattice. We discuss the relevance of these results to recent experimental studies of kagome
superconductors in the presence of an external
magnetic field.
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All authors Frederik A. S. Philipsen, Mats Barkman, Andreas Kreisel, Brian M. Andersen
Statistical Mechanics
A covariant fermionic path integral for scalar Langevin processes with multiplicative white noise
Daniel G. Barci, Leticia F. Cugliandolo and Zochil González Arenas
We revisit the construction of the fermionic path-integral representation of overdamped scalar Langevin processes with multiplicative white noise, focusing on the covariance of the generating functional under non-linear changes of variables. We identify the transformations of the auxiliary (commuting and anticommuting) variables that ensure covariance under such transformations. The subtleties induced by the non-differentiable trajectories of the
stochastic dynamics are encoded in the fermionic statistics. Upon integrating out the auxiliary variables, we derive the Onsager-Machlup formulation, which agrees with the one recently obtained using a higher-order discretization scheme. In contrast to the latter, the construction proposed here is formulated directly in continuous time.
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Materials Science
Atomic-Scale Surface Imaging of bulk Epitaxial CsPbBr3 Perovskite Single Crystals on Mica using Light Assisted Scanning Tunneling Microscopy at Low-Temperature (80 K)
Eric Duverger, Vladimir Bruevich, Vitaly Podzorov et al. (+1 more)
Epitaxial single-crystalline CsPbBr3 perovskite films on mica, prepared ex-situ, are explored using a low-temperature scanning tunneling microscope (STM) by probing the unoccupied electronic states of their surface in ultra-high
vacuum (UHV) at 80 K. Light-assisted STM measurements under a broadband illumination with visible light were employed to enhance and stabilize surface conductivity. STM imaging across the surface of macroscopic bulk CsPbBr3 films reveals large flat terraces characterized by a specific type of surface reconstruction, consisting of parallel rows of U-shaped atomic nanostructures. These structures are spaced by 12 angstroms and exhibit an internal periodicity of 5.1 angstroms. Density functional theory (DFT) calculations reproduce the experimental observations and reveal a competition between different orthorhombic CsPbBr3(110) surface reconstructions: a Cs-rich structure, identified as the most energetically stable, and three alternative PbBr rich reconstructions, which are slightly higher in energy yet remain consistent with the STM data. Additional analyses that explicitly account for the mica substrate exclude the cubic CsPbBr3 phase and other orthorhombic surface orientations, while showing that variations in the mica surface termination do not alter the preferred CsPbBr3(110) reconstruction. This combined approach thereby confirms our assignment and resolves previous STM interpretations of CsPbBr3.
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All authors Eric Duverger, Vladimir Bruevich, Vitaly Podzorov, Damien Riedel
Statistical Mechanics
Quantifying non-Markovianity in magnetization dynamics via entropy production rates
Felix Hartmann, Finja Tietjen, R. Matthias Geilhufe et al. (+1 more)
Magnetization dynamics is commonly described by the
stochastic Landau-Lifshitz-Gilbert (LLG) equation. On picosecond timescales, inertial and open-system extensions of the LLG equation are necessary to interpret recent experiments. We show analytically and numerically that the standard LLG equation exhibits strictly positive
entropy production rates, while inertial and open-system LLG dynamics display temporarily negative
entropy production rates indicating non-Markovianity. Here we quantify the degree of non-Markovianity using established measures. Our numerical calculations show that the open-system LLG equation consistently exhibits the highest magnitude of non-Markovianity for different initial conditions and
magnetic field orientations.
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All authors Felix Hartmann, Finja Tietjen, R. Matthias Geilhufe, Janet Anders
Soft Condensed Matter
Data-Driven Prediction of Dielectric Anisotropy in Nematic Liquid Crystals
Charles Parton-Barr and Richard J. Mandle
We curate a large-scale
dataset of low frequency dielectric anisotropy values for low molecular weight
liquid crystals. Using this
dataset, we demonstrate that supervised machine-learning models can predict dielectric anisotropy with substantially improved accuracy (RMSE 2.6) compared to estimates obtained from the Maier-Meier relations using molecular properties from both the widely used semiempirical AM1 method (RMSE 9.7) and the modern r2scan-3c composite method (RMSE 11.2). Realising the potential of machine learning techniques for
liquid crystalline materials requires carefully curated data to be accessible, and on this basis we propose a simple and standard template for reporting data.
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Superconductivity
Semiclassical theory for the orbital magnetic moment of superconducting quasiparticles
Jian-Hua Zeng, Zhongbo Yan, Zhi Wang et al. (+1 more)
We study the orbital
magnetic moment of Bogoliubov quasiparticles in
superconductors with the semiclassical approach. We derive the orbital
magnetic moment of a quasiparticle wavepacket by considering the energy correction of the wavepacket to the linear order of the
magnetic field. The semiclassical result is further verified by a linear response calculation with a full
quantum mechanical method. From the analytical expression we find that nontrivial structure in the superconducting pairing gap alone is unable to produce quasiparticle orbital
magnetic moment, which is in sharp contrast to the behavior of quasiparticle Berry
curvatures. We apply the formula to study a tight-binding model with
chiral $d$-wave superconducting gap, and show the influence of orbital
magnetic moment on the energy spectrum and local density of states. We also calculate the orbital Nernst effect driven by the interplay between the orbital
magnetic moment and the Berry
curvature of Bogoliubov quasiparticles.
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All authors Jian-Hua Zeng, Zhongbo Yan, Zhi Wang, Qian Niu
Materials Science
Chiral phonons in sixfold chiral CrSi$_2$: Raman spectroscopy and first-principles calculations
Gakuto Kusuno, Shingo Kisanuki, Yusuke Kousaka et al. (+2 more)
Chiral phonons have been identified in several
chiral crystals, primarily in those with trigonal
symmetry and threefold screw axes. In this study,
chiral phonons in CrSi$_2$, a
chiral crystal with a sixfold helical structure, were investigated. Circularly polarized Raman spectroscopy revealed a subtle splitting of doubly degenerate $E_2$
phonon modes between cross-circular polarization configurations. These observations, supported by first-principles
phonon calculations, indicate the presence of
chiral phonons in CrSi$_2$, expanding the scope of materials that exhibit
chiral vibrational modes beyond the conventional trigonal class.
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All authors Gakuto Kusuno, Shingo Kisanuki, Yusuke Kousaka, Yoshihiko Togawa, Takuya Satoh
Soft Condensed Matter · Cross-listed from cs.LG
Shortcut learning in geometric knot classification
Djordje Mihajlovic and Davide Michieletto
Classifying the
topology of closed curves is a central problem in low dimensional
topology with applications beyond mathematics spanning
protein folding,
polymer physics and even magnetohydrodynamics. The central problem is how to determine whether two
embeddings of a closed arc are equivalent under ambient isotopy. Given the striking ability of neural networks to solve complex classification tasks, it is therefore natural to ask if the
knot classification problem can be tackled using Machine Learning (ML). In this paper, we investigate generic shortcut methods employed by ML to solve the
knot classification challenge and specifically discover hidden non-topological features in training data generated through Molecular Dynamics simulations of polygonal
knots that are used by ML to arrive to positive classifications results. We then provide a rigorous foundation for future attempts to tackle the
knot classification challenge using ML by developing a publicly-available (i)
dataset, that aims to remove the potential of non-topological feature classification and (ii) code, that can generate
knot embeddings that faithfully explore chosen
geometric state space with fixed
knot topology. We expect that our work will accelerate the development of ML models that can solve complex
geometric knot classification challenges.
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Mesoscale and Nanoscale Physics
Emergence of a symmetry-broken Chern insulator near a moiré Kondo breakdown
Wanghao Tian, Bowen Shen, Lizhong Li et al. (+14 more)
Moiré
semiconductors built on angle-aligned transition metal dichalcogenide (TMD) heterobilayers provide a physical realization of the Kondo
lattice model, in which one TMD layer is prepared in a Mott insulating state supporting a
lattice of local
magnetic moments and the other layer in a metallic state supporting itinerant carriers. The artificial Kondo
lattice enables the exploration of exotic states of matter near a continuously tunable Kondo breakdown. Here we report the emergence of a
symmetry-broken Chern
insulator at a moiré hole filling factor 4/3 in angle-aligned MoTe2/WSe2 moiré
bilayers, which realize a
chiral Kondo
lattice. The
symmetry-broken Chern
insulator, which exhibits integer quantized
Hall conductance at a fractional moiré filling, breaks the translational
symmetry of the
lattice spontaneously; it also appears only near a
magnetic field-induced Kondo breakdown in the mixed-valence regime of the material. We further demonstrate that the
magnetic field required to induce the Kondo breakdown and to stabilize the
symmetry-broken Chern
insulator is twist angle dependent. The results present new opportunities for exploring the subtle interplay between
topology and Kondo interactions in moiré
semiconductors.
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All authors Wanghao Tian, Bowen Shen, Lizhong Li, Mingjie Zhang, Feng Liu, Chushan Li, Yaotian Liu, Fan Xu, Kenji Watanabe, Takashi Taniguchi, Peiling Li, Li Lu, Yang Xu, Shengwei Jiang, Tingxin Li, Jie Shan, Kin Fai Mak
Other Condensed Matter · Cross-listed from quant-ph
Detecting nonequilibrium phase transitions via continuous monitoring of space-time trajectories and autoencoder-based clustering
Erik Fitzner, Francesco Carnazza, Federico Carollo et al. (+1 more)
The characterization of collective behavior and nonequilibrium phase transitions in
quantum systems is typically rooted in the analysis of suitable system observables, so-called order parameters. These observables might not be known a priori, but they may in principle be identified through analyzing the
quantum state of the system. Experimentally, this can be particularly demanding as estimating
quantum states and expectation values of
quantum observables requires a large number of projective measurements. However, open
quantum systems can be probed in situ by monitoring their output, e.g. via heterodyne-detection or
photon-counting experiments, which provide space-time resolved information about their dynamics. Building on this, we present a machine-learning approach to detect nonequilibrium phase transitions from the measurement time-records of continuously-monitored
quantum systems. We
benchmark our method using the
quantum contact process, a model featuring an absorbing-state phase transition, which constitutes a particularly challenging test case for the
quantum simulation of nonequilibrium processes.
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All authors Erik Fitzner, Francesco Carnazza, Federico Carollo, Igor Lesanovsky
Materials Science · Cross-listed from physics.app-ph
g4chargeit: Geant4-based kinetic Monte Carlo simulations of charging in dielectric materials
Kush P. Gandhi, Advik D. Vira, William M. Farrell et al. (+5 more)
We present g4chargeit, a kinetic Monte Carlo framework built on Geant4 for self-consistent simulation of time-dependent electrostatic charging in dielectric materials. The model explicitly incorporates
stochastic particle transport and scattering processes using validated Geant4 cross-sections, while self-consistently evolving the electric potential and field. As a representative application, we simulate the charging of regolith grains under average dayside conditions on the Moon. The surface of the Moon, in addition to other airless planetary bodies, are regularly exposed to
solar ultraviolet
photons and
solar-wind
plasma, creating a radiation environment in which electrostatic interactions among regolith grains become significant. Until now, simulations of regolith charging have often relied on analytical approximations that oversimplify grain geometry and interaction mechanisms. Our Geant4-based simulations reveal charge accumulation within intergrain micro-cavities, leading to repulsive electrostatic forces consistent with experimental observations. The framework establishes a multiscale approach that links microscopic scattering events to the continuity equation of surface charge density and to the formation of macroscopic surface charge patches in complex grain geometries. Although demonstrated here for planetary regolith, the method is general and applicable to a broad range of dielectric charging problems. The code is openly available at https://github.com/kgandhi63/g4chargeit.git.
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All authors Kush P. Gandhi, Advik D. Vira, William M. Farrell, Nikolai Simonov, Alvaro Romero-Calvo, Thomas M. Orlando, Phillip N. First, Zhigang Jiang
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Dissipative charging of tight-binding quantum batteries
Mingdi Xu, Yiming Liu, Yefeng Song et al. (+2 more)
We investigate autonomous dissipative charging mechanisms for
lattice quantum batteries within the framework of open
quantum systems. Focusing on engineered Markovian dissipation, we show that appropriately designed Lindblad jump operators can drive tight-binding systems into highly excited band-edge states, resulting in steady states with large ergotropy. We illustrate this mechanism in a one-dimensional tight-binding chain and in a two-dimensional
graphene lattice. We find that disorder enhances the charging power, indicating that dissipation-assisted localization effects can be beneficial for energy storage. Moreover, the dissipative charging process remains robust against additional local dephasing noise. Our results establish bond dissipation as an effective and physically transparent mechanism for charging
lattice quantum batteries in realistic open-system settings.
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All authors Mingdi Xu, Yiming Liu, Yefeng Song, Xiang-Ping Jiang, Lei Pan
Materials Science
Unveiling Photoluminescence Signatures of Magneto-Optical Coupling in Layered Hybrid Manganese Chloride Perovskites
Yaiza Asensio, Samuele Mattioni, Daniel Vaquero et al. (+9 more)
Understanding the interplay between
magnetic ordering and light emission is crucial for developing magneto-optical technologies. However, this phenomenon is poorly understood since observations of this coupling vary significantly across materials. In this context, hybrid organic-inorganic metal halide perovskites (HOIPs) that incorporate Mn2+ ions are a chemically and structurally tunable platform for exploring this phenomenon, since they exhibit
magnetic ordering and photoluminescence (PL) emission. Here, we study two
antiferromagnetic Mn-based HOIPs with different organic cations that result in distinct
lattice stiffness, Mn2+-Mn2+ distance and octahedral distortion. Temperature-dependent PL excitation spectroscopy reveals changes in
crystal field splitting energy and Racah parameters well above the Néel temperature (TN), indicating the emergence of Mn2+-Mn2+
magnetic interactions prior to reach long-range
magnetic ordering. These variations align with the observed changes in temperature-PL
evolution. The compound with a more rigid
lattice shows stronger changes closer to TN, suggesting combined effects of
magnetic polarons and
spin-canting. In contrast,
magnetic polaron-induced
magnetic modifications prevail in the HOIP with a softer
lattice. These results reveal the complexity of the magneto-optical coupling in Mn-based HOIPs and provide new insights into this field extensible to other 2D materials that exhibit this phenomenon with potential for advanced magneto-optical applications.
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All authors Yaiza Asensio, Samuele Mattioni, Daniel Vaquero, Cédric A. Cordero-Silis, Houman Bahmani Jalali, Dorwal Marchelli, Marco Gobbi, Fèlix Casanova, Francesco Di Stasio, Marcos H.D. Guimarães, Luis E. Hueso, Beatriz Martín-García
Strongly Correlated Electrons
Orbital current signature using neutron diffraction
Dalila Bounoua, William Liège, Yvan Sidis et al. (+1 more)
We review the hallmarks of orbital loop currents in various correlated electron materials and how they have been evidenced using polarized
neutron diffraction. Over the last 20 years, loop current signatures have been observed in high temperature copper
oxide superconductors, iridates, copper
oxides spin ladders and recently kagome vanadate
superconductors. Such currents induce orbital
magnetic moments within the unit
cell of these
quantum materials that can be detected through their interaction with the
neutron spin. In addition to the usual description of orbital moments using point-like local
magnetic moments, we here show an alternative description of the
neutron magnetic cross-section involving the microscopic currents running between different atomic orbitals. We discuss the corresponding
magnetic structure factors and the resulting quantitative differences between both approaches.
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All authors Dalila Bounoua, William Liège, Yvan Sidis, Philippe Bourges
Materials Science
Effect of oxygen content on optical, structural, and dielectric properties of Al$_x$Ta$_y$O$_z$$ thin films
Pavel Ondračka, Richard Drevet, Daniel Franta et al. (+3 more)
This study reports on the optical, structural, and dielectric properties of aluminum tantalum
oxide (Al$_x$Ta$_y$O$_z$) thin films deposited at low temperature on silicon and steel substrates by pulsed direct current reactive magnetron sputtering of a target containing 80 at.% aluminum and 20 at.% tantalum in Ar/O$_2$ atmosphere. Oxygen flow rates ranging from 5.0 to 20 sccm corresponded to O content changes from 57.7 to 69.6 at.% and resulted in large differences in dielectric behavior, from films with no measurable dielectric strength to a dielectric strength of 231 V$\mu$m$^{-1}$, respectively. Ab initio calculations were employed to explain the large property changes, and we show that a decrease in the dielectric strength can be linked to the formation of metal-metal bonds in the material, when the O content is less than what would correspond to a stoichiometric Ta$_2$O$_5$ and Al$_2$O$_3$ mixture. The electronic states corresponding to the metal–metal bonds are located in the band gap close to the top of the valence band, leading to an effective band gap reduction, which is directly supported by X-ray photoelectron spectroscopy valence band measurements and by a broad optical absorption in the visible region.
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All authors Pavel Ondračka, Richard Drevet, Daniel Franta, Jan Dvořák, Ivan Ohlídal, Petr Vašina
Statistical Mechanics · Cross-listed from quant-ph
Optimal speed-up of multi-step Pontus-Mpemba protocols
Marco Peluso, Reinhold Egger and Andrea Nava
The classical Mpemba effect is the counterintuitive phenomenon where hotter water freezes faster than colder water due to the breakdown of Newton's law of cooling after a sudden temperature quench. The genuine nonequilibrium post-quench dynamics allows the system to evolve along effective shortcuts absent in the quasi-static regime. When the time needed for preparing the (classical or
quantum) system in the hotter initial state is included, we encounter so-called Pontus-Mpemba effects. We here investigate multi-step Pontus-Mpemba protocols for open
quantum systems whose dynamics is governed by non-autonomous (aka time-inhomogeneous) Lindblad master equations. In the limit of infinitely many steps, one arrives at continuous Pontus-Mpemba protocols. We study the crossover between the quasi-static and the sudden-quench regime, showing the presence of dynamically generated shortcuts achieved for time-dependent dissipation rates. Considering a two-parameter family of time-dependent rates, the parameters allowing for optimal speed-up conditions are determined. Time-dependent rates can also cause non-Markovian behavior, highlighting the existence of rich dynamical regimes accessible beyond the Markovian framework.
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Materials Science
Low-Field Ferroelectric Switching realised by Forced Harmonic Oscillation of Domain Walls
Niyorjyoti Sharma, Nathan Black, Joseph G. M. Guy et al. (+6 more)
Conventionally, dc fields are used for switching dipole orientations in ferroelectrics. Such fields tilt the potential surface experienced by domain walls and thereby lower activation energies for their movement: escape from tilted potential wells is then realised by thermal excitation, allowing a "creep" process of pinning and depinning to develop. Borrowing ideas of domain wall resonance from the
magnetic racetrack community, we show that ac fields, applied at the right frequency, can cause switching at much lower field magnitudes than dc ones (by factors of 4-5). Ferroelectric wall motion appears to be overdamped in the system studied (relaxor strontium barium niobate) and so the maximum in switching efficacy observed, at ~100 kHz, cannot be associated with resonant amplification, which needs an underdamped environment. Instead, in this high viscosity system, the frequency at which the maximum switching efficacy occurs seems to represent a compromise between the attempt frequency for wall depinning (which increases with frequency) and the extent to which energy is transferred to the wall within each field cycle (which decreases with frequency). Notwithstanding the absence of true resonance, the observation that ac excitation can dramatically reduce the bias levels needed for ferroelectric switching could still have significant ramifications for low energy
memory technology.
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All authors Niyorjyoti Sharma, Nathan Black, Joseph G. M. Guy, Eftihia Barnes, Kristina M. Holsgrove, Brian J. Rodriguez, Raymond G.P. McQuaid, J. Marty Gregg, Amit Kumar
Statistical Mechanics · Cross-listed from quant-ph
Les Houches lectures on random quantum circuits and monitored quantum dynamics
Romain Vasseur
These lecture notes are based on lectures given by the author at the Les Houches 2025 summer school on "Exact Solvability and
Quantum Information". The central theme of these notes is to apply the philosophy of statistical mechanics to study the dynamics of
quantum information in ideal and monitored random
quantum circuits – for which an exact description of individual realizations is expected to be generically intractable.
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Materials Science · Cross-listed from quant-ph
Near-single-domain superconducting aluminum films on GaAs(111)A with exceptional crystalline quality for scalable quantum circuits
Hsien-Wen Wan, Yi-Ting Cheng, Chao-Kai Cheng et al. (+6 more)
We have reproducibly grown near-single-domain superconducting aluminum (Al) films on GaAs(111)A wafers using molecular beam epitaxy. Synchrotron X-ray diffraction revealed twin-domain ratios of 0.00005 and 0.0003 for 19.4-nm- and 9.6-nm-thick films, respectively-the lowest reported for Al on any substrate and long considered unattainable for practical device platforms. Azimuthal scans across off-normal Al{$11\bar{1}$} reflections exhibit narrow full width at half maximum (FWHM) values down to $0.55^\circ$, unmatched by epi-Al grown by any other method. Normal scans showed a well-defined (111) orientation with pronounced Pendellösung fringes, and $\theta$-rocking-curve FWHM values down to $0.018^\circ$; the former indicates abrupt film-substrate and
oxide-film interfaces. Electron backscatter diffraction mapping confirms macroscopic in-plane uniformity and the absence of $\Sigma$3 twin domains. Atomic force microscopy and scanning transmission electron microscopy confirmed atomically smooth surfaces and abrupt heterointerfaces. The films exhibit critical temperatures approaching bulk values, establishing a materials platform for scalable, high-coherence superconducting
qubits.
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All authors Hsien-Wen Wan, Yi-Ting Cheng, Chao-Kai Cheng, Jui-Min Chia, Chien-Ting Wu, Sheng-Shiuan Yeh, Chia-Hung Hsu, Jueinai Kwo, Minghwei Hong
Strongly Correlated Electrons
High-temperature $\eta$-pairing superconductivity in the photodoped Hubbard model
Lei Geng, Aaram J. Kim and Philipp Werner
We investigate superconductivity emerging in the photodoped Mott insulating Hubbard model using steady-state dynamical mean-field theory implemented on the real-frequency axis. By employing high-order strong-coupling
impurity solvers, we obtain the nonequilibrium phase diagram for photoinduced $\eta$-pairing superconductivity with a remarkably high effective critical temperature. We further identify a superconducting gap in the momentum-resolved spectral function and optical conductivity, providing spectroscopic signatures accessible to experiments. Our results highlight a route to a controllable form of high-temperature superconductivity in nonequilibrium strongly correlated systems, fundamentally distinct from the
equilibrium $s$-wave pairing state in the attractive Hubbard model or cuprate-like $d$-wave
superconductors.
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Materials Science
Photocatalytic methanol dehydrogenation promoted synergistically by atomically dispersed Pd and clustered Pd
Zhuyan Gao, Tiziano Montini, Junju Mu et al. (+4 more)
Supported metal in the form of single atoms, clusters, and particles can individually or jointly affect the activity of supported heterogeneous catalysts. While the individual contribution of supported metal to the overall activity of supported photocatalysts has been identified, the joint activity of mixed metal species is overlooked because of their different photoelectric properties. Here, atomically dispersed Pd (Pd1) and Pd clusters are loaded onto CdS, serving as oxidation and reduction sites, respectively, for methanol dehydrogenation. The Pd1 substitutes Cd2+, forming hole-trapping states for methanol oxidation and assisting the dispersion of photo-deposited Pd clusters. Therefore, methanol dehydrogenation on CdS with supported Pd1 and Pd clusters exhibits the highest turnover frequency of 1.14 s-1 based on Pd content, and affords H2 and HCHO with a similar apparent
quantum yield of 87 +/- 1% at 452 nm under optimized reaction conditions. This work highlights the synergistic catalysis of supported metal for improved photocatalytic activity.
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All authors Zhuyan Gao, Tiziano Montini, Junju Mu, Nengchao Luo, Emiliano Fonda, Paolo Fornasiero, Feng Wang
Materials Science
Wide-Surface Furnace for In Situ X-Ray Diffraction of Combinatorial Samples using a High-Throughput Approach
Giulio Cordaro, Juande Sirvent, Cristian Mocuta et al. (+7 more)
The combinatorial approach applied to functional
oxides has enabled the production of material libraries that formally contain infinite compositions. A complete ternary diagram can be obtained by pulsed
laser deposition (PLD) on 100 mm silicon wafers. However, interest in such materials libraries is only meaningful if high-throughput characterization enables the information extraction from the as-deposited library in a reasonable time. While much commercial equipment allows for XY-resolved characterization at room temperature, very few sample holders have been made available to investigate structural, chemical, and functional properties at high temperatures in controlled atmospheres. In the present work, we present a furnace that enables the study of 100 mm wafers as a function of temperature. This furnace has a dome to control the atmosphere, typically varying from nitrogen gas to pure oxygen atmosphere with external control. We present the design of such a furnace and an example of X-ray diffraction (XRD) and fluorescence (XRF) measurements performed at the DiffAbs beamline of the SOLEIL synchrotron. We apply this high-throughput approach to a combinatorial library up to 735 {\textdegree}C in nitrogen and calculate the thermal expansion coefficients (TEC) of the ternary system using custom-made MATLAB codes. The TEC analysis revealed the potential limitations of Vegard's law in predicting
lattice variations for high-
entropy materials.
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All authors Giulio Cordaro, Juande Sirvent, Cristian Mocuta, Fjorelo Buzi, Thierry Martin, Federico Baiutti, Alex Morata, Albert Tarancòn, Dominique Thiaudière, Guilhem Dezanneau