Statistical Mechanics
Spreading fronts: numerical simulations on discrete models and continuous equations
J. M. Marcos
Out-of-
equilibrium systems, inherently complex and challenging to understand, are prevalent across various disciplines, including physics where they arise in contexts such as fluid dynamics. In particular, critical out-of-
equilibrium systems combine this complexity with the scaling laws and universality classes observed in critical phenomena, with kinetic surface roughening, the study of how a flat surface becomes progressively rougher over time, serving as a
prime example. This behavior manifests in a wide variety of contexts, including metal corrosion,
cell proliferation, and, notably, the growth of thin films, which can emerge as a result of wetting processes. In this thesis, we conduct extensive numerical simulations to study critical fluctuations and identify universal features of several rough interfaces, generated by simulating discrete models of thin film growth and by performing direct numerical integration of continuum equations. To explore the universal behavior of these interfaces, we identify the critical exponents that characterize the spatio-temporal fluctuations of the front. Additionally, we analyze the dynamics of thin films across different physical scenarios to deepen our understanding of their behavior in out-of-
equilibrium conditions, especially in the case where these films are formed by the action of an external force such as Surface Acoustic Waves.
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Materials Science · Cross-listed from quant-ph
Bright Single-Photon Emission from Individual Tin-Vacancy Centers in Multi-Cone Diamond Waveguides
Pablo Tieben, Jan Rhensius, Takuya F. Segawa et al. (+5 more)
Diamonds containing color centers have recently gathered significant
attention for photonic
quantum technologies, including
quantum sensing, photonic
quantum computers, and
quantum networks. Among the various color centers, tin-vacancy (SnV) centers are particularly promising due to the high emission efficiency from the zero-
phonon line and due to their long
spin coherence times. However, the extraction of
photons from diamond remains a key challenge. Here we demonstrate high
photon extraction from a single SnV center incorporated in a diamond nanopillar with tapered sidewalls and a multi-cone structure. A sharp emission peak with a full width at half maximum (FWHM) of $6\,$nm was observed at a wavelength of $619\,$nm. Furthermore, the second-order correlation function exhibited an antibunching dip well below $g^{(2)}(0) = 0.5$, indicating single-
photon emission. Remarkably, the emitter achieved a high saturation count rate of approximately $9\,$Mcps. These results establish our nanopillar platform as a promising candidate for bright and stable
quantum sources and sensors based on SnV centers in diamond.
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All authors Pablo Tieben, Jan Rhensius, Takuya F. Segawa, Risei Abe, Konosuke Shimazaki, Shigeki Takeuchi, Andeas W. Schell, Hideaki Takashima
Materials Science · Cross-listed from cs.CV
A Large-Language-Model Assisted Automated Scale Bar Detection and Extraction Framework for Scanning Electron Microscopic Images
Yuxuan Chen, Ruotong Yang, Zhengyang Zhang et al. (+2 more)
Microscopic characterizations, such as Scanning Electron Microscopy (SEM), are widely used in scientific research for visualizing and analyzing microstructures. Determining the scale bars is an important first step of accurate SEM analysis; however, currently, it mainly relies on manual operations, which is both time-consuming and prone to errors. To address this issue, we propose a multi-modal and automated scale bar detection and extraction framework that provides concurrent object detection, text detection and text recognition with a Large
Language Model (LLM)
agent. The proposed framework operates in four phases; i) Automatic
Dataset Generation (Auto-DG) model to synthesize a diverse
dataset of SEM images ensuring robust training and high generalizability of the model, ii) scale bar object detection, iii) information extraction using a hybrid Optical Character Recognition (OCR) system with DenseNet and Convolutional Recurrent Neural Network (CRNN) based
algorithms, iv) an LLM
agent to analyze and verify accuracy of the results. The proposed model demonstrates a strong performance in object detection and accurate localization with a precision of 100%, recall of 95.8%, and a mean Average Precision (mAP) of 99.2% at IoU=0.5 and 69.1% at IoU=0.5:0.95. The hybrid OCR system achieved 89% precision, 65% recall, and a 75% F1 score on the Auto-DG
dataset, significantly outperforming several mainstream standalone engines, highlighting its reliability for scientific image analysis. The LLM is introduced as a
reasoning engine as well as an intelligent assistant that suggests follow-up steps and verifies the results. This automated method powered by an LLM
agent significantly enhances the efficiency and accuracy of scale bar detection and extraction in SEM images, providing a valuable tool for microscopic analysis and advancing the field of scientific imaging.
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All authors Yuxuan Chen, Ruotong Yang, Zhengyang Zhang, Mehreen Ahmed, Yanming Wang
Materials Science
Optimizing Cross-Domain Transfer for Universal Machine Learning Interatomic Potentials
Jaesun Kim, Jinmu You, Yutack Park et al. (+11 more)
Accurate yet transferable machine-learning interatomic potentials (MLIPs) are essential for accelerating materials and chemical discovery. However, most universal MLIPs overfit to narrow
datasets or computational protocols, limiting their reliability across chemical and functional domains. We introduce a transferable multi-domain training strategy that jointly optimizes universal and task-specific parameters through selective regularization, coupled with a domain-bridging set (DBS) that aligns potential-energy surfaces across
datasets. Systematic ablation experiments show that small DBS fractions (0.1%) and targeted regularization synergistically enhance out-of-distribution generalization while preserving in-domain fidelity. Trained on fifteen open databases spanning molecules,
crystals, and surfaces, our model, SevenNet-Omni, achieves state-of-the-art cross-domain accuracy, including adsorption-energy errors below 0.06 eV on metallic surfaces and 0.1 eV on metal-organic frameworks. Despite containing only 0.5% r$^2$SCAN data, SevenNet-Omni reproduces high-fidelity r$^2$SCAN energetics, demonstrating effective cross-functional transfer from large PBE
datasets. This framework offers a scalable route toward universal, transferable MLIPs that bridge
quantum-mechanical fidelities and chemical domains.
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All authors Jaesun Kim, Jinmu You, Yutack Park, Yunsung Lim, Yujin Kang, Jisu Kim, Haekwan Jeon, Suyeon Ju, Deokgi Hong, Seung Yul Lee, Saerom Choi, Yongdeok Kim, Jae W. Lee, Seungwu Han
Mesoscale and Nanoscale Physics
Should it really be that hard to model the chirality induced spin selectivity effect?
J. Fransson
The chirality induced
spin selectivity effect remains a challenge to capture with theoretical modeling. While at least a decade was spent on independent electron models, which completely fail to reproduce the experimental results, the lesson to be drawn out of these efforts is that a correct modeling of the effect has to include interactions among the electrons. In the discussion of the phenomenon ones inevitably encounters the Onsager reciprocity and time-reversal
symmetry, and questions whether the observations violate these fundamental concepts, or whether we have not been able to identify what it is that make those concepts redundant in this context. The experimental fact is that electrons
spin-polarize by one or another reason, when traversing
chiral molecules. The set-ups are simple enough to enable effective modeling, however, overcoming the grand failures of the theoretical efforts, thus far, and formulating a theory which is founded on microscopic modeling appears to be a challenge. A discussion of the importance of electron correlations is outlined, pointing to possible spontaneous breaking of time-reversal
symmetry and Onsager reciprocity.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Tunable multi-photon correlations from a coherently driven quantum dot
Thomas K. Bracht, Rachel N. Clark, Petros Androvitsaneas et al. (+7 more)
Mixing the fields generated by different light sources has emerged as a powerful approach for engineering non-Gaussian
quantum states. Understanding and controlling the resulting
photon statistics is useful for emerging
quantum technologies that are underpinned by interference. In this work, we investigate intensity correlation functions arising from the interference of resonance fluorescence from a
quantum emitter with a coherent
laser field. We show that the observed bunching behavior results from a subtle interplay between
quantum interference and the normalization of the correlation functions. We show that by adjusting the mixing ratio and phase one can achieve full tunability of the second-order correlation, ranging from anti-bunching to bunching. We further extend our analysis to third-order correlation functions, both experimentally and theoretically, to provide new insights into the interpretation of higher-order correlations and offer practical tools for shaping
quantum optical fields.
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All authors Thomas K. Bracht, Rachel N. Clark, Petros Androvitsaneas, Matthew Jordan, Samuel G. Bishop, Harry E. Dyte, Moritz Cygorek, Ian A. Farrer, Doris E. Reiter, Anthony J. Bennett
Strongly Correlated Electrons
Spinon band flattening by its emergent gauge field in quantum kagome ice
Masafumi Udagawa and Roderich Moessner
Fractional excitations provide a key to identifying sought-after topological
quantum spin liquid states in realistic materials. Their single-particle dynamics already presents a challenging many-body problem on account of the coupling to their emergent gauge field. Here, we study the spinon excitations of kagome ice, realized at the $2/3$ magnetization plateau of
spin ice, by combining up-to-$63$-site exact diagonalization with an analytical state graph mapping. We find a macroscopically degenerate mode in the spinon spectrum. It originates from the destructive interference due to the interaction with surrounding gauge fields, a form of many-body caging. We explicitly construct, and count, the concomitant many-body wave functions. Finally, we discuss the possible role of these flat modes in the magnetization process of kagome antiferromagnets, in particular with regard to the asymmetric termination of the kagome ice magnetisation plateau.
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Soft Condensed Matter
Thin-film flows of granular suspensions on a solid surface
Alice Pelosse, Elisabeth Guazzelli and Matthieu Roché
This review article examines the complex dynamics of thin-film flows of granular suspensions spreading over rigid solid substrates with free air interfaces. Such systems feature an involved coupling of the free-surface dynamics with the flow and microstructure of the suspension. In particular, we develop two canonical thin-film situations: drop spreading and dip-coating. In drop spreading, confinement of the particulate phase near the advancing contact line alters both the spreading rate and the interface shape. In dip-coating, understanding the entrainment of fluid and particles becomes challenging as the film thickness approaches the particle size.
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Materials Science
In-plane polar domains enhanced energy storage
Yu Lei, Xiaoming Shi, Sihan Yan et al. (+16 more)
Relaxor ferroelectric thin films are recognized for their ultrahigh power density, rendering them highly promising for energy storage applications in electrical and electronic systems. However, achieving high energy storage performance with chemically homogeneous, environmentally friendly and compositionally stable materials remains challenging. In this work, we present a design of dielectrics with high energy storage performance via an in-plane polar domains incorporating polar nanoregions mechanism. Guided by phase-field simulations, we synthesized La/Si co-doping BaTiO3 solid-solution thin films with high chemical homogeneity to realize high energy storage performance. Given that, we achieve a high energy density of 203.7J/cm3 and an energy efficiency of approximately 80% at an electric field of 6.15MV/cm. This mechanism holds significant promise for the design of next-generation high-performance dielectric materials for energy storage and other advanced functional materials.
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All authors Yu Lei, Xiaoming Shi, Sihan Yan, Qinghua Zhang, Jiecheng Liu, Sixu Wang, Yu Chen, Jiaou Wang, He Qi, Qian Li, Ting Lin, Jingfen Li, Qing Zhu, Haoyu Wang, Jing Chen, Lincong Shu, Linkun Wang, Han Wu, Xianran Xing
Mesoscale and Nanoscale Physics
Local-Antisymmetric Flat Band and Coexisting Correlated stripe charge orders in WSe2-Modulated Twisted Bilayer Graphene
Chi Zhang, Shihao Zhang, Mengmeng Zhang et al. (+2 more)
Insulating, atomically flat transition metal dichalcogenides (TMDs) like WSe2 are ideal substrates for probing intrinsic
graphene properties. Conventionally, their influence on
graphene's band structure is assumed negligible, particularly when small moire patterns form. Combining scanning tunneling microscopy/spectroscopy and theoretical analysis, we reveal that the atomic registry in
graphene/WSe2
heterostructures profoundly modulates the electronic structure of magic-angle twisted
bilayer graphene (MATBG). At special
graphene/WSe2 twist angles, an incommensurate moire superlattice hosts three distinct atomic stacking configurations (A, B, X types). These induce position-dependent potentials that asymmetrically shift MATBG's flat bands, transforming them from hole-side to electron-side asymmetric within a single AA-stacked region. This
symmetry breaking enables the unprecedented coexistence of orthogonal stripe charge orders in the correlated regime-a phenomenon previously considered mutually exclusive due to Coulomb repulsion. This band modulation arises from the synergistic effects of the
graphene/WSe2 interfacial atomic registry and heterostrain within the MATBG, exhibiting multi-field tunability. Our work establishes interfacial atomic registry as a critical, previously overlooked tuning parameter for flat-band physics, opening avenues to engineer correlated
quantum states in van der Waals
heterostructures.
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All authors Chi Zhang, Shihao Zhang, Mengmeng Zhang, Lin He, Qi Zheng
Materials Science
Entropy Engineering-Regulated Electron-Phonon Coupling for Highly Efficient Photoluminescence in Se-doped WS2
Chi Zhang, Quan Shen, Mengmeng Zhang et al. (+8 more)
The limited
quantum yield of strained monolayer transition metal dichalcogenides grown by vapor-phase methods and during transfer-based stacking poses a fundamental challenge for their optoelectronic applications. Here, we introduce the concept of "
entropy engineering" as a transformative strategy to selectively enhance light-matter interactions through controlled electron-
phonon coupling. We unveil how tailored
entropy introduced via precise selenium doping or interfacial van der Waals proximity can significantly amplify radiative recombination from momentum-dark
excitons in WS2 monolayers. Notably, we discover that slight selenium doping drastically enhances the photoluminescence (PL) of WS2 under strain. While both undoped and heavily doped WS2 suffer from strong PL quenching owing to the direct-to-indirect bandgap transition, lightly Se-doped samples exhibit an order-of-magnitude increase in emission intensity. This counterintuitive boost is traced to doping-induced structural disorder, which intensifies electron-
phonon interactions and unlocks efficient
phonon-assisted emission from otherwise non-radiative indirect
excitons. Moreover, we demonstrate that van der Waals coupling to adjacent Se-doped layers can impart interfacial
entropy and further augment PL via proximity effects. Our work highlights
entropy engineering via controlled doping as a powerful strategy for activating high-efficiency light emission in atomically thin
semiconductors.
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All authors Chi Zhang, Quan Shen, Mengmeng Zhang, Zhiming Deng, Taishen Wu, Xuying Zhong, Gang Ouyang, Dongsheng Tang, Qi Zheng, Jiansheng Dong, Weichang Zhou
Materials Science
Frenkel anomaly on co-ordination numbers in liquid CO2 at 100 and 1000 bar studied by Monte Carlo simulation using Kihara potential model
Koji Kobashi
An issue concerning the Frenkel line of
liquid CO2 is that its location has not been unequivocally determined. So far, reliable Frenkel lines were identified from velocity autocorrelation functions (VAFs) computed by Molecular Dynamic simulations; however VAFs cannot be directly verified experimentally. By contrast, the co-ordination numbers (CNs) can be measured experimentally by X-ray and
neutron scattering or computed by Monte Carlo (MC) simulation, and thus provide an alternative means of determining the location of the Frenkel line. In the present study, the CNs were computed by MC simulation using the Kihara potential, and the Frenkel anomalies were identified at {P = 100 bar, T = 260 K}, in good agreement with previous results based on VAFs, and at {P = 1000 bar, T = 370 K}, which deviates significantly from them.
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Strongly Correlated Electrons
Collinear, incommensurate antiferromagnetism in van der Waals magnet alpha-UTe3
H. Sakai, C. Tabata, K. Kaneko et al. (+5 more)
alpha-UTe3, a van der Waals (vdW) actinide compound with a monoclinic ZrSe3-type structure, is a narrow-gap
semiconductor with 5f moments. 125Te NMR reveals strongly anisotropic, layer-confined
spin fluctuations below about 20 K, with the a-axis component enhanced, and a signal wipeout at the
antiferromagnetic (AFM) transition at TN = 5 K. Single-
crystal neutron diffraction finds q approx. (0.17, 0.5, 0) and a longitudinal sinusoidal modulation of a-axis moments (amplitude about 0.8 muB) with AFM stacking along b. A CEF singlet-singlet induced-moment framework accounts for the easy-axis anisotropy, the small heat-capacity anomaly at TN, the reduced ordered moment, and the exchange-driven selection of q in this localized 5f vdW magnet, establishing a constrained exchange geometry stabilizing this in-plane incommensurate state.
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All authors H. Sakai, C. Tabata, K. Kaneko, Y. Tokiwa, T. Kitazawa, S. Kambe, Y. Tokunaga, Y. Haga
Superconductivity · Cross-listed from physics.app-ph
Loss investigations of high frequency lithium niobate Lamb wave resonators at ultralow temperatures
Wenbing Jiang, Xuankai Xu, Jiazhen Pan et al. (+5 more)
Lamb wave resonators (LWRs) operating at ultralow temperatures serve as promising acoustic platforms for implementing microwave-optical transduction and
radio frequency (RF) front-ends in aerospace communications because of the exceptional electromechanical coupling (k^2) and frequency scalability. However, the properties of LWRs at cryogenic temperatures have not been well understood yet. Herein, we experimentally investigate the temperature dependence of the quality factor and resonant frequency in higher order antisymmetric LWRs down to millikelvin temperatures. The high-frequency A1 and A3 mode resonators with spurious-free responses are comprehensively designed, fabricated, and characterized. The quality factors of A1 modes gradually increase upon cryogenic cooling and shows 4 times higher than the room temperature value, while A3 mode resonators exhibit a non-monotonic temperature dependence. Our findings provide new insights into loss mechanisms of cryogenic LWRs, paving the way to strong-coupling
quantum acoustodynamics and next-generation satellite wireless communications.
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All authors Wenbing Jiang, Xuankai Xu, Jiazhen Pan, Hancong Sun, Yu Guo, Huabing Wang, Libing Zhou, Tao Wu
Superconductivity
Phase-sensitive evidence for pair density waves in a kagome superconductor
Xiao-Yu Yan, Guowei Liu, Hanbin Deng et al. (+22 more)
Pair density wave (PDW) exhibits periodic amplitude and sign modulations of the superconducting order parameter. Such a pairing state has long been proposed to be highly sensitive to nonmagnetic scattering, but its experimental realization remains elusive. Here we discover a nonmagnetic PDW-breaking effect in a kagome
superconductor, using designer atomic nonmagnetic
impurities and high-precision scanning tunneling microscopy (STM) at a base temperature of 30mK. We detect 2x2 pair density modulations by Josephson STM with a superconducting tip and 2x2 pairing gap modulations by normal STM. We find that the pairing modulations in both cases are substantially suppressed upon doping the kagome
lattice with dilute isovalent nonmagnetic
impurities, whereas the charge order and uniform superconductivity remain robust. We further identify the correlation between atomic dopants and the local suppression of PDW. We attribute these findings to a nonmagnetic pair-breaking effect, arising from the phase modulation of PDW in the kagome d-orbital. Taken together with its signatures in other state-of-the-art spectroscopy and transport measurements linked by theory, our findings support the ground state of the kagome
superconductor as a correlated topological phase with superconducting loop currents.
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All authors Xiao-Yu Yan, Guowei Liu, Hanbin Deng, Xitong Xu, Haiyang Ma, Hailang Qin, Junyi Zhang, Yuanyuan Zhao, Xiuhao Fan, Wei Song, Muwei Gao, Haitian Zhao, Zhe Qu, Yigui Zhong, Kozo Okazaki, Xiquan Zheng, Yingying Peng, Zurab Guguchia, Xianxin Wu, Da Wang, Qiang-Hua Wang, Hendrik Hohmann, Matteo Dürrnagel, Ronny Thomale, Jia-Xin Yin
Soft Condensed Matter
Impact of elastic inhomogeneity on collective dynamical properties investigated by field theoretical description in real space
Cunyuan Jiang
Interpreting the vibrational properties of amorphous solids beyond Debye's theory is challenging due to the presence of inhomogeneity on the mesoscopic scale. In this work, we model this inhomogeneity by real-space fluctuating elasticity with a spatially correlated distribution and calculate the dynamical properties using an exact real-space field theoretical approach. Our results clarify that the excess low-frequency density of states (DOS) originates from a selective scattering effect (stronger scattering of short wavelengths) induced by elastic inhomogeneity. The visualization of the local DOS in real space reveals the existence of anomalous modes, highly excited spots, at low frequencies. The findings regarding these highly excited spots and the selectivity of the correlation length were missed in previous perturbative field approaches in wave-vector space, and they align with recent progress from particle-level simulations and experiments. These results provide concrete insights into the low-frequency vibrational anomaly of amorphous solids from the perspective of simple elastic inhomogeneity.
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Materials Science
Generalized quantum limits of electrical contact resistance and thermal boundary resistance
Alice Ho, Jashan Singhal, Deji Akinwande et al. (+2 more)
The importance of electrical contact resistance and thermal boundary resistance has increased dramatically as devices are scaled to atomic limits. The use of a rich range of materials with various bandstructures (e.g.
parabolic, conical), and in geometries exploiting various dimensionalities (e.g. 1D wires, 2D sheets, and 3D bulk) will increase in the future. Here we derive a single general expression for the
quantum limit of electrical contact resistivity for various bandstructures and all dimensions. A corresponding result for the
quantum limit of thermal boundary resistance is also derived. These results will be useful to quantitatively co-design,
benchmark, and guide the lowering of electrical and thermal boundary resistances for energy efficient devices.
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All authors Alice Ho, Jashan Singhal, Deji Akinwande, Huili Grace Xing, Debdeep Jena
Materials Science
Delayed 1T to 2H Phase Transition Upon Electrochemical Delithiation of LiMoS2
Yerin Hong, Juhwan Lim, Jinhong Min et al. (+4 more)
Molybdenum disulfide (MoS2) is a widely studied layered material for electronic, optical, and catalytic applications. It can host lithium ions between the van der Waals layers, which triggers a phase transition between the semiconducting 2H phase and metallic 1T phase. While lithium insertion triggers a phase transition to the 1T phase, the phase behavior upon electrochemical lithium removal is not resolved. In this work, we conduct single-flake electrochemical (de)lithiation of MoS2 using microelectrode arrays. Through both electrochemical voltage analysis and correlative Raman spectroscopy, we show that an electrochemically cycled and delithiated MoS2 flake initially remains in the 1T phase. However, over the course of several days, it transitions back into the thermodynamically stable 2H phase. This result resolves the phase transformation pathway upon delithiation and showcases the ability to electrochemically synthesize the metastable 1T-MoS2 phase.
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All authors Yerin Hong, Juhwan Lim, Jinhong Min, Nishkarsh Agarwal, Robert Hovden, Ageeth A. Bol, Yiyang Li
Mesoscale and Nanoscale Physics
Two-dimensional flat-bands in Moire-diamonds
Yalan Wei, Shifang Li, Yuke Song et al. (+1 more)
The discovery of flat-bands in magic-angle twisted
bilayer graphene has underscored the potential of moire engineering for correlated states, but such phases are notoriously difficult to realize and highly fragile against perturbations. Here, we propose an alternative route to flat-bands by introducing sp3 hybridization in twisted graphite. Instead of relying on fine-tuned magic angles, our approach identifies flat-band states at relatively large twist angles with short moire periods. In this regime, sp3-induced reconstructions generate electronic states that, once formed, are locked by substantial energy barriers, rendering them robust against external perturbations. Using twisted graphite as a prototype, we uncover a series moire-diamond that host two-dimensional flat conduction of valence bands, where carriers are localized within specific momentum planes but remain dispersive along orthogonal directions. The emergence of dimensional flat-bands opens a new platform for flat-band-driven correlated physics and suggests opportunities for designing
quantum materials with highly directional electronic functionalities.
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All authors Yalan Wei, Shifang Li, Yuke Song, Chaoyu He
Superconductivity
Possible Spatial Correlation of Superconducting and Pseudogap Dynamics in a Bi-based Cuprate
T. Shimizu, T. Kurosawa, S. Tsuchiya et al. (+5 more)
Understanding the interplay between superconductivity and the pseudogap phase is essential for elucidating the mechanism of high-temperature superconductivity in cuprates. Here we provide direct spatial evidence that these two states are locally and intrinsically correlated. Using spatially and temporally resolved measurements of photoinduced quasiparticle dynamics in optimally doped Bi$_2$Sr$_{1.7}$La$_{0.3}$CuO$_{6+\delta}$ (La-Bi2201), we reveal micrometer-scale spatial contrasts in the transient reflectivity that arise from local variations in the threshold fluence required to disrupt either the superconducting or pseudogap state. The superconducting response remains spatially uniform, whereas the pseudogap exhibits intrinsic inhomogeneity, yet the spatial variations of their threshold fluences closely track each other, establishing a robust local correlation between the two. These results introduce a bulk-sensitive ultrafast optical methodology for visualizing hidden spatial correlations in correlated materials and provide new
benchmarks for understanding the intertwined phases in cuprates.
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All authors T. Shimizu, T. Kurosawa, S. Tsuchiya, R. Tobise, K. Yamane, R. Morita, M. Oda, Y. Toda
Mesoscale and Nanoscale Physics · Cross-listed from math.AP
Hydrodynamics of degenerate Fermi gases on spherical Fermi surfaces
Benjamin Anwasia and Diogo Arsénio
We consider the description of a
Fermi gas of free electrons given by the Boltzmann–
Fermi–Dirac equation, and aim at providing a precise mathematical understanding of the
Fermi ground state and its first-order approximation of excited states on the
Fermi sphere. In order to achieve that, using the framework of hydrodynamic limits in collisional kinetic theory, we identify the low-temperature regimes in which charge-density fluctuations concentrate on the
Fermi sphere. In three spatial dimensions or higher, we also characterize the thermodynamic equilibra and energy spectra of fluctuations. This allows us to derive the macroscopic hydrodynamic equations describing how charge densities flow and propagate in metals, thereby providing a precise description of
plasma oscillations in conductors. The two-dimensional case is fundamentally different and is handled in a companion article. Remarkably, our results establish that excited electrons and their energy can be distributed on the
Fermi sphere anisotropically, which deviates from the common intuitive assumption that electrons and their energy should be distributed uniformly in all directions. The hydrodynamic regimes featured in this work are akin to the acoustic limit of the classical Boltzmann equation. However, we emphasize that our derivation holds for arbitrarily fast rates of convergence of the Knudsen number, which significantly extends the applicability of the known proofs of the classical acoustic limit. This suggest that low-temperature limits of
Fermi gases provide a promising avenue of research toward a complete understanding of the compressible Euler limit.
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Superconductivity
Magnetic Field-Enhanced Graphene Superconductivity with Record Pauli-Limit Violation
Jixiang Yang, Omid Sharifi Sedeh, Chiho Yoon et al. (+22 more)
Spin-polarized
superconductors offer a rare platform for studying electronic correlations, but few candidate systems have been experimentally confirmed to date. Here, we report the observation of a
spin-polarized superconducting state, denoted SC5, in WSe2-proximitized rhombohedral trilayer
graphene. At in-plane
magnetic field B|| = 0 T, SC5 has a critical temperature of 68 mK and an out-of-plane critical
magnetic field of only 12 mT. Surprisingly, these values are significantly enhanced as B|| increases, and the superconductivity persists to B|| = 8.8 T. This value corresponds to a record-high Pauli-limit violation ratio of at least 80 among all
superconductors, while the true critical field is beyond the limit of our instrument. We conclude that SC5 experiences a canting crossover from Ising-type to
spin-polarized
superconductor with increased B||.
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All authors Jixiang Yang, Omid Sharifi Sedeh, Chiho Yoon, Shenyong Ye, Henok Weldeyesus, Armel Cotten, Tonghang Han, Zhengguang Lu, Zach Hadjri, Junseok Seo, Lihan Shi, Emily Aitken, Prayoga P Liong, Zhenghan Wu, Mingchi Xu, Christian Scheller, Mingyang Zheng, Rasul Gazizulin, Kenji Watanabe, Takashi Taniguchi, Dominique Laroche, Mingda Li, Fan Zhang, Dominik M. Zumbühl, Long Ju