Materials Science · Cross-listed from physics.chem-ph
Nano-electronvolt Fourier-limited transition of a single surface-adsorbed molecule
Masoud Mirzaei, Alexey Shkarin, Burak Gurlek et al. (+7 more)
High-resolution spectroscopy allows one to probe weak interactions and to detect subtle phenomena. While such measurements are routinely performed on atoms and molecules in the gas phase, spectroscopy of adsorbed species on surfaces is faced with challenges. As a result, previous studies of surface-adsorbed molecules have fallen short of the ultimate resolution, where the transition linewidth is determined by the lifetime of the excited state. In this work, we conceive a new approach to surface deposition and report on
Fourier-limited electronic transitions in single dibenzoterrylenes adsorbed onto the surface of an anthracene
crystal. By performing spectroscopy and super-resolution microscopy at
liquid helium temperature, we shed light on various properties of the adsorbed molecules. Our experimental results pave the way for a new class of experiments in surface science, where high spatial and spectral resolution can be combined.
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All authors Masoud Mirzaei, Alexey Shkarin, Burak Gurlek, Johannes Zirkelbach, Ashley J. Shin, Irena Deperasińska, Boleslaw Kozankiewicz, Tobias Utikal, Stephan Götzinger, Vahid Sandoghdar
Disordered Systems and Neural Networks · Cross-listed from quant-ph
Universal energy-space localization and stable quantum phases against time-dependent perturbations
Hongye Yu and Tzu-Chieh Wei
Stability against perturbations is a highly nontrivial property of
quantum systems and is often a requirement to define new phases. In most systems where stability can be rigorously established, only static perturbations are considered; whether any system can remain stable against generic time-dependent perturbations is largely elusive. In this work, we identify a universal phenomenon in driving $q$-local
Hamiltonians called energy-space localization and prove that it can survive under generic time-dependent perturbations, where the evolving state is exponentially localized in an energy window of the instantaneous spectrum. For
spin glass models where the configuration spaces are separated by large energy barriers, the localization in energy spaces can induce a true localization in configuration spaces and robustly break ergodicity. We then demonstrate its applications in several systems with such barriers. For certain LDPC codes, we show that the system remains localized near the original codeword for an exponentially long time even under generic time-dependent perturbations. For classical optimization problems with clustered solution space, the stability becomes an obstacle for
quantum Hamiltonian-based
algorithms to escape local minima. Our work provides a new lens for analyzing non-
equilibrium dynamics of generic
quantum systems, and versatile mathematical tools for establishing stability and for designing
quantum algorithms.
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Disordered Systems and Neural Networks
Nonequilibrium DC Current Generation in a Driven Dissipative Haldane Model
Konrad Koenigsmann, Sankha Subhra Bakshi, Peter Schauss et al. (+1 more)
The interplay of
topology with nonequilibrium driving and dissipation in open
quantum systems has recently attracted significant interest in condensed matter physics. In this work, we investigate a driven, dissipative Haldane model using large-scale numerical simulations of Lindblad dynamics. We show that the system evolves into a time-periodic quasi-steady state when subjected to driving and dissipation, with nonequilibrium band occupations. To characterize this regime, we introduce an occupation-weighted Chern number as a nonquantized diagnostic constructed from the steady-state occupations and the geometry of the unperturbed bands. We further analyze charge transport in the presence of simultaneous driving and damping and demonstrate that a finite DC bulk current emerges when inversion
symmetry is broken by a staggered sublattice potential. The magnitude and direction of this current are controlled by the driving amplitude, revealing a tunable nonequilibrium transport response enabled by inversion-
symmetry breaking.
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All authors Konrad Koenigsmann, Sankha Subhra Bakshi, Peter Schauss, Gia-Wei Chern
Soft Condensed Matter · Cross-listed from physics.bio-ph
Topological edge currents promote exploratory search in microtubule dynamic instability
Chongbin Zheng, Jaime Agudo-Canalejo, Jonathon Howard et al. (+1 more)
Microtubules capture chromosomes during mitosis by stochastically switching between growth and shrinkage at catastrophe events. They display strikingly rich biochemistry and dynamics, regulated by a stabilizing cap with distinct conformational states. Microtubule lengths at catastrophe are observed to follow a peaked distribution, while their growth "stutters" briefly before catastrophe. Such complexity makes it hard to capture all these observations without a large number of tunable parameters. Here, we introduce a topological model of the microtubule cap that reproduces the features above through dynamical edge states, that provides a minimal description with just two free parameters. Our approach further provides an analytical description of catastrophes and allows the same features to persist over a wide range of tubulin concentration, consistent with experimental observations.
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All authors Chongbin Zheng, Jaime Agudo-Canalejo, Jonathon Howard, Evelyn Tang
Materials Science
Turn-on of Current-Induced Spin Torque upon Noncollinear Antiferromagnetic Ordering in Delafossite PdCrO2
Xiaoxi Huang, Qi Song, Gautam Gurung et al. (+10 more)
We report measurements of the current-induced
spin torque produced by the delafossite antiferromagnet PdCrO2 and acting on an adjacent
ferromagnetic permalloy layer. The
spin torque increases strongly as the temperature is reduced through the Neel temperature, when the PdCrO2 transitions from a paramagnetic phase to a noncollinear
antiferromagnetic state. This result is qualitatively consistent with density functional theory calculations regarding how
spin-current generation changes upon
antiferromagnetic ordering in PdCrO2.
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All authors Xiaoxi Huang, Qi Song, Gautam Gurung, Daniel A. Pharis, Thow Min Jerald Cham, Yulan Chen, Rakshit Jain, Maciej Olszewski, Yufan Feng, Amal El-Ghazaly, Evgeny Y. Tsymbal, Darrell G. Schlom, Daniel C. Ralph
Statistical Mechanics
Elementary derivation of the dissipation-coherence bound for stochastic oscillators
Artemy Kolchinsky
The dissipation-coherence bound is a conjectured tradeoff between
entropy production and the quality of
stochastic oscillations. We show that this bound can be derived by combining the higher-order “thermodynamic uncertainty relation” with a simple condition on phase-current fluctuations. In one-dimensional cyclic systems, our proposed condition is shown to be equivalent to the dissipation-coherence bound itself. Our approach yields an elementary proof in the weak-noise Gaussian regime and extends naturally to some non-Gaussian systems, as we illustrate with a run-and-tumble particle. Finally, we contrast current-based and spectral formulations of the dissipation-coherence bound.
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Soft Condensed Matter
Low-Power Temperature Control by Chiral Ferroelectric Nematic Liquid Crystal Windows
Md Sakhawat Hossain Himel, Rohan Dharmarathna, Netra Prasad Dhakal et al. (+5 more)
Low power consumption is critical for smart windows for temperature control and
privacy. The recently discovered ferroelectric nematic
liquid crystals exhibit strong coupling of the ferroelectric polarization with electric fields, making them promising candidates for energy-efficient electrochromic devices. Here we investigate the electrochromic properties of a room temperature
chiral ferroelectric nematic
liquid crystal in films with in-plane electrodes, where the electric field is perpendicular to the helical axis. We demonstrate that smart windows based on this material can regulate interior temperatures within a 10 Celsius range using only 50 milliwatt per square meter specific power, achieving fifty percent larger temperature modulation and 50-100 times lower power consumption than
polymer dispersed and
polymer stabilized
liquid crystal windows. These findings suggest that
chiral ferroelectric nematic
liquid crystals offer a highly efficient approach for smart window applications, potentially surpassing existing electrochromic technologies in energy efficiency and thermal regulation.
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All authors Md Sakhawat Hossain Himel, Rohan Dharmarathna, Netra Prasad Dhakal, Kelum Perera, Samuel Sprunt, James T. Gleeson, Robert J. Twieg, Antal Jákli
Mesoscale and Nanoscale Physics
Towards a unified mechanistic understanding of the electrical response of bipolar nanofluidic systems
Ayelet Ben-Kish Sharvit and Yoav Green
Bipolar nanoporous membranes and bipolar nanochannels are used in water desalination and energy-harvesting systems that provide clean water and green energy, respectively. The growing need for both requires continuous improvement of their performance. However, the underlying physics of these complex systems is still not fully understood, making empirical optimization slow and inefficient. In this work, we combine theoretical analysis and numerical simulations to develop a unified framework for improving the design of nanofluidic devices. We show that the system response is governed by the interplay between the applied voltage and a parameter $\eta$, which depends on the ratio of geometry and surface charge densities of both charged regions. At low voltages, the response is mostly determined by $\eta$, allowing its dependence to be represented by a simplified phase space. At high voltages, this phase space becomes oversimplified. To demonstrate the framework's robustness, we scan a range of configurations, from unipolar channels (single charged region) to bipolar channels (positive and negative segments). We compare the numerically simulated current-voltage responses with three theoretical models, which are limiting scenarios within the phase space, and explain the observed deviations. These findings can help reduce the time and resources required to optimize nanofluidic devices and improve the interpretation of experiments and simulations.
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Mesoscale and Nanoscale Physics
Comparative study of phonon-limited carrier transport in the Weyl semimetal TaAs family
Shashi B. Mishra, Zhe Liu, Sabyasachi Tiwari et al. (+2 more)
We present a systematic first-principles study of
phonon-limited transport in the TaAs family of Weyl semimetals using the ab initio Boltzmann transport equation. The calculated electrical conductivities show excellent agreement with experimental data for high-quality samples, confirming that transport in these systems is predominantly limited by
phonon scattering. Among the four compounds, NbP achieves the highest conductivity, governed primarily by its large
Fermi velocities that offset its stronger scattering rates. In contrast, TaAs displays the lowest conductivity, linked to reduced carrier pockets and limited carrier velocities. Additionally, NbP conductivity remains largely unaffected by small hole or electron doping, whereas TaAs exhibits pronounced electron-hole asymmetry. NbAs and TaP show intermediate behavior, reflecting their
Fermi surface
topologies and scattering phase space. These findings provide microscopic insight into the transport mechanisms of the TaAs family and emphasize the critical role of
phonons, doping, and carrier dynamics in shaping their electronic response.
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All authors Shashi B. Mishra, Zhe Liu, Sabyasachi Tiwari, Feliciano Giustino, Elena R. Margine
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Nonlinear near-field spectroscopy of exciton-polaritons in a van der Waals layered waveguide
Valeriy I. Kondratyev, Vanik Shahnazaryan, Mikhail Tyugaev et al. (+6 more)
Layered van der Waals materials offer novel opportunities for on-chip waveguiding and development of integrated photonic
circuits. In the strong light-matter coupling regime, their nonlinear response can be significantly enhanced, which is crucial for developing active photonic devices. However, probing the nonlinearity of waveguide modes in subwavelength-thick structures is challenging as they are not directly accessible from far-field. Here we apply a novel nonlinear near-field spectroscopic technique based on a GaP solid immersion lens and femtosecond
laser excitation to study nonlinearity of guided modes in monolayer WS$_2$ encapsulated in hBN under the strong light-matter coupling regime. We reveal formation of
exciton-polaritons with $\sim 50$ meV Rabi splitting and demonstrate a pump-induced transition from strong to weak coupling. Our results show that
exciton resonance saturation and broadening lead to an efficient nonlinear response of guided polaritons, which can be employed for developing compact van der Waals photonic switches and modulators.
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All authors Valeriy I. Kondratyev, Vanik Shahnazaryan, Mikhail Tyugaev, Tatyana V. Ivanova, Ivan E. Kalantaevskii, Dmitry V. Permyakov, Ivan V. Iorsh, Anton K. Samusev, Vasily Kravtsov
Materials Science · Cross-listed from math.RT
Representation of tensor functions using lower-order structural tensor set: three-dimensional theory
Mohammad Madadi and Pu Zhang
The representation theory of tensor functions is a powerful mathematical tool for constitutive modeling of anisotropic materials. A major limitation of the traditional theory is that many point groups require fourth- or sixth-order structural tensors, which significantly impedes practical engineering applications. Recent advances have introduced a reformulated representation theory that enables the modeling of anisotropic materials using only lower-order structural tensors (i.e., second-order or lower). Building upon the reformulated theory, this work establishes the representations of tensor functions for three-dimensional centrosymmetric point groups. For each point group, we propose a lower-order structural tensor set and derive the representations of tensor functions explicitly. For scalar-valued and second-order symmetric tensor-valued functions, our theory is indeed applicable to all three-dimensional point groups because their representations are determined by the corresponding centrosymmetric groups. The representation theory presented here is broadly applicable for constitutive modeling of anisotropic materials.
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Materials Science
CBVB-nH complexes as prevalent defects in metal-organic vapor-phase epitaxy-grown hexagonal boron nitride
Marek Maciaszek and Bartłomiej Baur
Optically active defects in hexagonal boron nitride (hBN) are promising candidates for active components in emerging
quantum technologies, such as single-
photon emitters and
spin centers. However, further progress in hBN-based
quantum technologies requires a deeper understanding of the physics and chemistry of hBN defects. In this work, we employ ab initio calculations to investigate the thermodynamic stability and optical properties of defect complexes involving carbon, boron vacancies, and hydrogen. We demonstrate that the formation of CBVB-nH complexes (n from 0 to 3) is energetically favorable under nitrogen-rich conditions in the presence of carbon and hydrogen. The low formation energies and high binding energies of these complexes arise from the strong electrostatic attraction between the positively charged carbon substitutional defect (CB) and the negatively charged hydrogen-passivated boron vacancies (VB-nH). These complexes are particularly likely to form in metal-organic vapor-phase epitaxy (MOVPE)-grown samples, where growth occurs in the presence of carbon and hydrogen and is accompanied by a high density of boron vacancies. The optical properties of CBVB-nH complexes are analyzed and compared to recent photoluminescence measurements on MOVPE-grown hBN samples. In particular, we investigate the origin of the emission peaks at 1.90 eV and 2.24 eV and demonstrate that both the energies and lineshapes are consistent with hole capture by negatively charged CBVB and CBVB-H complexes.
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Statistical Mechanics · Cross-listed from quant-ph
Temporal Entanglement Transitions in the Periodically Driven Ising Chain
Karun Gadge, Abhinav Prem and Rishabh Jha
Periodically driven
quantum systems can host non-
equilibrium phenomena without static analogs, including in their
entanglement dynamics. Here, we discover $temporal$ $entanglement$ $transitions$ (TET) in a Floquet
spin chain, which correspond to a
quantum phase transition in the spectrum of the
entanglement Hamiltonian and are signaled by dynamical spontaneous
symmetry breaking. We identify the
symmetry principles underlying these transitions: they appear when the driven
Hamiltonian preserves global
symmetry (here, $\mathbb{Z}_2$), the initial state respects this
symmetry, and the reduced density
matrix carries weight in both subsystem-parity sectors, with TET occurring precisely when the sector weights become equal (given the previous two conditions are also satisfied). Intriguingly, we find these transitions across a broad range of driving frequencies (from adiabatic to high-frequency regime) and independently of drive details, where they manifest as periodic, sharp
entanglement spectrum reorganizations marked by the Schmidt-gap closure, a vanishing
entanglement echo, and
symmetry-
quantum-number flips, while remaining invisible to conventional local observables. At high frequencies, the
entanglement Hamiltonian acquires an intrinsic timescale decoupled from the drive period, rendering the transitions genuine steady-state features. Finite-size scaling reveals universal critical behavior with correlation-length exponent $\nu=1$, matching
equilibrium Ising universality despite its emergence from purely dynamical mechanisms decoupled from static criticality. Our work establishes TET as novel features in Floquet
quantum matter.
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Disordered Systems and Neural Networks · Cross-listed from hep-th
Subdimensional Disorder and Logarithmic Defect
Soichiro Shimamori and Yifan Wang
We study quenched disorder localized on a $p$-dimensional subspacetime in a $d$-dimensional conformal field theory. Motivated by the logarithmic behavior often associated with disorder, we introduce a defect setup in which bulk local operators transform in ordinary conformal representations, while defect local operators assemble into logarithmic multiplets. We refer to such objects as logarithmic defects and investigate their model-independent properties dictated solely by conformal
symmetry and its representation theory, including correlation functions, logarithmic defect operator expansions, and conformal blocks. As a concrete example, we analyze the free scalar theory with a generalized pinning defect subject to random coupling fluctuations, and we identify a half-line of fixed points describing the corresponding logarithmic conformal defects. Along the way, we propose a candidate monotone governing defect renormalization group flows induced by subdimensional disorder, and demonstrate its consistency with such flows in the free theory across various dimensions. We further comment on generalizations and outline a broader program for bootstrapping logarithmic defects.
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Mesoscale and Nanoscale Physics
Unconventional criticality in $O(D)$-invariant loop-constrained Landau theory
Svitlana Kondovych, Asle Sudbø and Flavio S. Nogueira
We study an unconventional phase transition in ferroelectrics where the polarization field is constrained to be divergence-free, allowing only loop-like configurations. This local constraint fundamentally alters the critical behavior, driving the system beyond the Landau-Ginzburg-Wilson paradigm. A renormalization group analysis shows that the polarization acquires an unusually large anomalous dimension, $\eta\approx 0.239$ in three dimensions, far exceeding the typical values in $O(3)$-invariant systems. We attribute this effect to a naturally induced gauge
symmetry originating from the zero divergence constraint. Such gauge-field behavior is reminiscent of fractionalized phases, revealing a fundamental connection between constrained ferroelectrics and emergent gauge phenomena in correlated matter.
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Statistical Mechanics · Cross-listed from quant-ph
Quantum State Designs via Magic Teleportation
Hugo Lóio, Guglielmo Lami, Lorenzo Leone et al. (+3 more)
We investigate how non-stabilizer resources enable the emergence of
quantum state designs within the projected ensemble. Starting from initial states with finite magic and applying resource-free Clifford
circuits to scramble them, we analyze the ensemble generated by performing projective Pauli measurements on a subsystem of the final state. Using both analytical arguments and large-scale numerics, we show that the projected ensemble converges towards a state $k$-design with an error that decays exponentially with the $k$-th Stabilizer Rényi
Entropy of the pre-measurement state, via a Magic-Induced Design Ansatz (MIDA) that we introduce. We identify a universal scaling form, valid across different classes of magic initial states, and corroborate it through numerical simulations and analytical calculations of the frame potential. For finite-depth Clifford
unitaries, we show that the timescales at which state designs emerge are controlled by the transport of magic. We identify a “magic teleportation” mechanism whereby non-Clifford resources injected locally spread through Clifford scrambling and measurements across distances beyond the lightcone. Our results demonstrate how a small and controlled amount of magic suffices to generate highly random states, providing a systematic route toward generating
quantum state designs in early fault-tolerant devices.
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All authors Hugo Lóio, Guglielmo Lami, Lorenzo Leone, Max McGinley, Xhek Turkeshi, Jacopo De Nardis
Strongly Correlated Electrons
Yamaji effect in models of underdoped cuprates
Jing-Yu Zhao, Shubhayu Chatterjee, Subir Sachdev et al. (+1 more)
Recent angle-dependent magnetoresistance measurements in underdoped cuprates have revealed compelling evidence for small hole pockets in the pseudogap regime, including observation of the Yamaji effect in HgBa$_2$CuO$_{4+\delta}$ (Chan et al., Nature Physics 10.1038/s41567-025-03032-2 (2025)). A key distinction between theories is their predicted
Fermi volumes, measured as fractions of the square
lattice Brillouin zone: $p/4$ per pocket for
spin density wave (SDW) versus $p/8$ for fractionalized
Fermi liquid (FL*), where $p$ is the hole doping. We calculate the $c$-axis magnetoresistance $\rho_{zz}(\theta, \phi)$ within the semiclassical Boltzmann formalism for both states, and using the ancilla layer model (ALM) for FL* in a single-band
Hamiltonian. The results from the $\text{FL}^*$ phase show good consistency with current experimental data. Conversely, the results for the SDW phase are highly sensitive to the ordering momentum along the $z$-direction. An ordering vector of $Q = (\pi, \pi, \pi)$ yields predictions that starkly disagree with the experiment. The only possibility for agreement within the SDW scenario is to assume an ordering momentum of $Q = (\pi, \pi, 0)$. However, even in this specific case, the SDW scenario predicts a marginally smaller Yamaji angle at $\phi=0$ than the FL* theory, and a second Yamaji peak near in-plane angle $\phi = 45^\circ$, which was not observed in the experiment. In reality, the Néel ordering vector is likely uncorrelated between adjacent layers, so that there is no coherent interlayer transport of hole-pocket quasiparticles in the SDW scenario, and consequently no Yamaji effect. Our results support the FL* interpretation of
Fermi arcs in the pseudogap phase, and establish Yamaji angle measurements as a discriminatory tool between theoretical models.
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All authors Jing-Yu Zhao, Shubhayu Chatterjee, Subir Sachdev, Ya-Hui Zhang
Strongly Correlated Electrons · Cross-listed from hep-th
Diffeomorphism invariant tensor networks for 3d gravity
Vijay Balasubramanian and Charlie Cummings
Tensor networks prepare states that share many features of states in
quantum gravity. However, standard constructions are not diffeomorphism invariant and do not support an
algebra of non-commuting area operators. Recently, analogues of both problems were addressed in a tensor network discretization of topological field theories (TFT) with finite or compact gauge groups. Here, we extend this work towards
gravity by generalizing to gauge groups that are discrete or continuous, compact or non-compact. Applied to $\text{SL}(2,\mathbb{R}) \times \text{SL}(2,\mathbb{R})$ Chern-Simons theory, our construction can be interpreted as building states of three dimensional
gravity with a negative cosmological constant. Our tensor networks prepare states that satisfy the constraints of Chern-Simons theory. In metric variables, this implies that the states we construct satisfy the Wheeler-DeWitt equation and momentum constraints, and so are diffeomorphism invariant.
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Quantum Gases · Cross-listed from quant-ph
Observation of area laws in an interacting quantum field simulator
Maciej T. Jarema, Mohammadamin Tajik, Jörg Schmiedmayer et al. (+2 more)
Information shared between parties quantifies their correlation. The encoding of correlations across space and time characterises the structure, history, and interactions of systems. One of the most fundamental properties that emerges from studies of information is the area law, which states that information shared between spatial subregions typically scales with the area of their boundary rather than their volume. In non-interacting,
quantum many-body systems, where Gaussian statistics apply, the scaling of information measures is well understood. Within interacting systems, the readout of information measures is impeded by the complexity of state reconstruction. As such, no measurements beyond small
quantum systems (e.g., composed of few, localised particles) have been made. Here, we fill this gap by experimentally demonstrating the area law of mutual information in an ultra-cold atom simulator of
quantum fields with tuneable interaction strength. Our results detail the scaling of mutual information with subsystem volume, boundary area, and separation between spatial regions at finite temperature. Moreover, we quantify the total effect of non-Gaussian correlations using an information-theoretic measure - relative
entropy. Our presented approach is data-driven, model agnostic, and readily applicable to other platforms and observables, thus constituting a universal toolkit for probing information in high-dimensional
quantum systems and its role in shaping
quantum matter and spacetime.
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All authors Maciej T. Jarema, Mohammadamin Tajik, Jörg Schmiedmayer, Silke Weinfurtner, Tobias Haas
Materials Science
Structure and magnetism of MnGe thin films grown with a nonmagnetic CrSi template
B. D. MacNeil, J. S. R. McCoombs, D. Kalliecharan et al. (+7 more)
We report a method to grow B20 MnGe thin films using molecular-beam epitaxy, which employs an ultrathin CrSi template layer on Si(111). This layer is expected to be nonmagnetic, in contrast to MnSi and FeGe buffer layers that have been used previously. This template layer permits an investigation of the intrinsic properties of MnGe in the ultrathin-film limit without the influence of a neighboring
magnetic layer. Single-phase MnGe(111) films were grown with thicknesses between 2 and 40 nm, which exhibited low interfacial roughnesses on the order of 0.6 nm. The films crystallized in a B20 structure with a small rhombohedral distortion. Magnetometry measurements in out-of-plane fields are consistent with a cone phase derived from helimagnetic order propagating along the film normal. However, an unexpected remanent moment develops below 35K, concomitant with features in the field dependence of the transport data. This provides indirect evidence for the presence of a low-temperature phase which has been identified by others as either a triple-Q topological
spin-hedgehog
lattice, or a multidomain single-Q helical state.
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All authors B. D. MacNeil, J. S. R. McCoombs, D. Kalliecharan, J. Myra, M. Pula, J. F. Britten, G. B. G. Stenning, K. Gupta, G. M. Luke, T. L. Monchesky
Materials Science
Resonant diffraction and photoemission inconsistent with altermagnetism in epitaxial RuO$_2$ films
Benjamin Z. Gregory, Neha Wadehra, Shuyuan Zhang et al. (+15 more)
Excitement about the
magnetic and electronic properties of RuO$_2$ is growing, fueled by reports of antiferromagnetism, strain-induced superconductivity, and its recent classification as a member of a newly proposed
magnetic class, altermagnets, with RuO$_2$ widely regarded as the paradigmatic example. Nevertheless, the
magnetic ground state of RuO$_2$ remains contentious, as several recent experiments report no evidence of
magnetic order. To address this discrepancy, we performed resonant elastic scattering measurements on a series of epitaxial RuO$_2$ thin films grown on the (100)-plane of TiO$_2$ substrates across a range of strain states. Leveraging full polarization control and azimuthal scans of the structurally forbidden 100 Bragg reflection, we systematically tested for signatures of colinear
antiferromagnetic order. We found that the resonant elastic scattering signal in RuO$_2$ thin films likely originates from anisotropic charge scattering, not long-range
antiferromagnetic order. Using angle-resolved photoemission spectroscopy we uncover a band structure without altermagnetic band splitting that is consistent with a nonmagnetic phase. Similarly, anisotropic magnetoresistance results show no evidence of magnetism. The combination of three independent measurements suggests the absence of altermagnetism in RuO$_2$.
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All authors Benjamin Z. Gregory, Neha Wadehra, Shuyuan Zhang, Yi Wu, Samuel Poage, Jörg Strempfer, Asish K. Kundu, Anil Rajapitamahuni, Elio Vescovo, Anita Verma, Betül Pamuk, Jacob Ruf, Hari Nair, Nathaniel J. Schreiber, Kaveh Ahadi, Kyle M. Shen, Darrell G. Schlom, Andrej Singer
Mesoscale and Nanoscale Physics
Optical Response of Graphene Quantum Dots in the Visible Spectrum: A Combined DFT-QED Approach
J. Olivo, J. Blengino Albrieu and Mauro Cuevas
We propose a model based on density functional theory (DFT) and
quantum electrodynamics (QED) to study the dynamical characteristics of
graphene quantum dots (GQDs). We assume the GQD edges are saturated with hydrogen atoms, effectively making it a polycyclic aromatic hydrocarbon (PAH) such as coronene. By combining the GQD spectrum calculated from a time-dependent DFT (TDDFT) with the dynamical behavior of a QD model derived from QED, we calculate the main optical characteristics of the GQD, such as its transition frequencies, the dipole moment associated to each of those transitions, life-time and the population dynamics of the molecular levels. Owing to the close match between the calculated spectrum and experimental results, our results represent a significant contribution to research on
quantum treatments of light-matter interactions in realistic 2D nanomaterials.
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Strongly Correlated Electrons
Structural origin of resonant diffraction in RuO$_2$
Connor A Occhialini, Christie Nelson, Alessandro Bombardi et al. (+12 more)
We report Ru L$_3$-edge resonant X-ray diffraction studies on single
crystal and (001) epitaxial films of RuO$_2$. We investigate the distinct $\mathbf{Q} = (100)$ and $(001)$ reflections as a function of incident energy, azimuthal angle, and temperature. The results show that the observed resonant diffraction in RuO$_2$ is fully consistent with a resonant charge anisotropy signal of structural origin permitted by the parent (non-
magnetic) rutile $P4_2/mnm$ space group. These results significantly constrain the
magnetic contribution to the resonant diffraction signal and indicate the unlikely existence of $\mathbf{k} = 0$
antiferromagnetic order in RuO$_2$.
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All authors Connor A Occhialini, Christie Nelson, Alessandro Bombardi, Shiyu Fan, Raul Acevedo-Esteves, Riccardo Comin, Dmitri N Basov, Maki Musashi, Masashi Kawasaki, Masaki Uchida, Hoydoo You, John Mitchell, Valentina Bisogni, Claudio Mazzoli, Jonathan Pelliciari
Materials Science · Cross-listed from math.MG
Continuous invariant-based asymmetries of periodic crystals quantify deviations from higher symmetry
Surya Majumder, Daniel Widdowson, Yury Elkin et al. (+4 more)
Ideal
symmetry is known to break down under almost any noise. One measure of asymmetry in a periodic
crystal is the relative multiplicity Z' of geometrically non-equivalent units. However, Z' discontinuously changes under almost any displacement of atoms, which can arbitrarily scale up a primitive
cell. This discontinuity was recently resolved by a hierarchy of invariant descriptors that continuously change under all small perturbations. We introduce a Continuous Invariant-based Asymmetry (CIA) to quantify (in physically meaningful Angstroms) the deviation of a periodic
crystal from a higher
symmetry form. Our experiments on several
Crystal Structure Prediction
datasets show that about a half of simulated
crystals have high values of CIA, while all experimental structures in these
datasets have CIA=0. On another hand, many
crystals with high values Z' in the Cambridge Structural Database (CSD) turned out to be close to more symmetric forms with Z'<=1 due to low values of CIAs.
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All authors Surya Majumder, Daniel Widdowson, Yury Elkin, Olga Anosova, Andrew I Cooper, Graeme M Day, Vitaliy Kurlin
Quantum Gases
Breaking of scale invariance in a strongly dipolar 2D Bose gas
Haoting Zhen, Yifei He, Sampriti Saha et al. (+4 more)
Two-dimensional (2D) dipolar atomic gases present unique opportunities for exploring novel
quantum phases due to their anisotropic and long-range interactions. However, the behavior of strongly dipolar Bose gases in 2D remains unclear, especially when dipoles are tilted. Here, we demonstrate the creation and characterization of strongly dipolar 2D condensates in a quasi-2D harmonic trap with tunable dipole orientation. By investigating scale invariance properties through breathing collective mode measurements, we observe significant breaking of scale invariance when dipoles are tilted in-plane indicating the dominance of the nonlocal dipole-dipole interactions (DDIs) in this regime. Interestingly, the breaking of the scale invariant dynamics is accompanied by an increase in
quantum fluctuations, as shown by comparison with mean-field and beyond mean-field theoretical studies. Our experiments also reveal that at critical tilt angles around 70{\deg}, stripe-type density modulations emerge, suggesting the presence of a roton spectrum in 2D, while the system still shows hydrodynamic nature with the phase-locking breathing behavior. This observation elucidates the many-body effect induced by DDIs in 2D, thus marking a crucial step toward realizing 2D supersolids and other exotic
quantum phases.
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All authors Haoting Zhen, Yifei He, Sampriti Saha, Mithilesh K. Parit, Mingchen Huang, Nicolò Defenu, Gyu-Boong Jo
Materials Science
Scalable and deterministic construction of moiré superlattice in 2D materials using stressor films
Yu-Mi Wu, Sihun Lee, Yufeng Xi et al. (+6 more)
Moiré superlattice in two-dimensional (2D) materials provides a powerful platform to engineer emergent electronic states, yet the construction of moiré superlattices remains lab-scale, involving much trial and error and with little control. Here, we demonstrate the construction of a heterostrain-induced moiré superlattice in transition metal dichalcogenides using a scalable process that deterministically induces strain to 2D materials. By applying patterned thin-film stressors and probing the resulting structures with scanning transmission electron microscopy, we directly resolve the induced heterostrain,
lattice deformations, and stacking variations that produce the moiré superlattice. We find that uniaxial and biaxial heterostrain give rise to distinct moiré patterns, including stripes and distorted hexagonal patterns. With this approach, we create in-plane polar distortions and thus in-plane polarization at the domain boundaries of the moiré superlattice in MoS$_2$. The deterministic and scalable construction of moiré patterns using a well-established scalable process opens opportunities to design new moiré geometries in 2D materials.
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All authors Yu-Mi Wu, Sihun Lee, Yufeng Xi, Stephen D. Funni, Saif Siddique, Natalie L. Williams, Giovanni Sartorello, Hesam Askari, Judy J. Cha
Materials Science
Strain-induced Moiré Reconstruction and Memorization in Two-Dimensional Materials without Twist
Nazmul Hasan, Tara Peña, Aditya Dey et al. (+7 more)
Two-dimensional (2D) materials with a twist between layers exhibit a moiré interference pattern with larger periodicity than any of the constituent layer unit
cells. In these systems, a wealth of exotic phases appear that result from moiré-dependent many-body electron correlation effects or non-trivial band
topology. One problem with using twist to generate moiré interference has been the difficulty in creating high-quality, uniform, and repeatable samples due to fabrication through mechanical stacking with viscoelastic stamps. Here we show, a new method to generate moiré interference through the controlled application of layer-by-layer strain (heterostrain) on non-twisted 2D materials, where moiré interference results from strain-induced
lattice mismatch without twisting or stacking. Heterostrain generation is achieved by depositing stressed thin films onto 2D materials to apply large strains to the top layers while leaving layers further down less strained. We achieve deterministic control of moiré periodicity and
symmetry in non-twisted 2D multilayers and
bilayers, with 97% yield, through varying stressor film force (film thickness X film stress) and geometry. Moiré reconstruction effects are memorized after the removal of the stressor layers. Control over the strain degree-of-freedom opens the door to a completely unexplored set of unrealized tunable moiré
geometric symmetries, which may now be achieved in a high-yield and user-skill independent process taking only hours. This technique solves a long-standing throughput bottleneck in new moiré
quantum materials discovery and opens the door to industrially-compatible manufacturing for 2D moiré-based electronic or optical devices.
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All authors Nazmul Hasan, Tara Peña, Aditya Dey, Dongyoung Yoon, Zakaria Islam, Yue Zhang, Maria Vitoria Guimaraes Leal, Arend M. van der Zande, Hesam Askari, Stephen M. Wu
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Spin Readout in a 22 nm Node Integrated Circuit
Isobel C. Clarke, Virginia Ciriano-Tejel, David J. Ibberson et al. (+7 more)
Constructing a
quantum computer capable of broad and important applications is likely to require millions of addressable physical
qubits, posing the challenge of large-scale integration of
quantum systems with classical electronics. Fully depleted silicon-on-
insulator CMOS technology has been used to develop a range of cryogenic electronic components for the control and readout of different
qubit modalities interfaced on separate chips. However, recent measurements of
quantum dots on this technology raise the tantalising prospect of realising control electronics and
spin qubits on the same manufacturing platform, within a single integrated
circuit (IC). Here, we demonstrate single-shot
spin readout in addressable
quantum dot devices within an IC fabricated using industry-standard 22 nm fully depleted silicon-on-
insulator technology. We achieve
spin-to-charge conversion via a ramped energy-selective measurement, detected using a
radio-frequency single-electron transistor and addressed by on-chip cryogenic electronics. The observation of consistent readout visibilities exceeding 90% and millisecond
spin relaxation times in two nominally identical devices within the addressable array supports the reproducibility of the unit
cell. The successful observation of
spin readout using this CMOS process marks a key step towards realising highly scalable and integrated
spin qubits.
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All authors Isobel C. Clarke, Virginia Ciriano-Tejel, David J. Ibberson, Grayson M. Noah, Thomas H. Swift, Mark A. I. Johnson, Ross C. C. Leon, Alberto Gomez-Saiz, John J. L. Morton, M. Fernando Gonzalez-Zalba
Strongly Correlated Electrons
Excitonic correlations in the equilibrium and voltage-biased bilayer Hubbard model: multi-orbital two-particle self-consistent approach
Jiawei Yan, Jonas B. Profe, Yuta Murakami et al. (+1 more)
We develop a nonequilibrium multi-orbital extension of the two-particle self-consistent theory and apply it to the
bilayer Hubbard model as a minimal platform to investigate correlation effects in the presence of interlayer interactions and tunneling. The method determines vertex corrections in the
spin and charge channels self-consistently at the two-particle level, thereby avoiding the spurious finite-temperature phase transitions that limit dynamical mean-field theory in two dimensions. We derive the spectral self-energy and implement the framework directly on the real-frequency axis within the Keldysh nonequilibrium Green's function formalism, enabling the treatment of both
equilibrium and non-
equilibrium steady states without relying on numerical analytic continuation. As an application, we demonstrate that a pseudogap can emerge in the
bilayer Hubbard model when
spin, charge, or excitonic fluctuations become sufficiently strong. Instabilities in different channels are also evaluated in an unbiased manner across the parameter space. Remarkably, we find that the excitonic susceptibility grows with increasing interlayer bias, before it gets suppressed at large biases by the charge imbalance between the layers. This work establishes a versatile and computationally efficient framework for investigating correlated multi-orbital systems under nonequilibrium conditions.
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All authors Jiawei Yan, Jonas B. Profe, Yuta Murakami, Philipp Werner
Mesoscale and Nanoscale Physics
Excitonic optical absorption in strained monolayer CrSBr
Maurício F. C. Martins Quintela, Guilherme J. Inacio, Miguel Sá et al. (+5 more)
Recently, the isolation of 2D
magnetic materials has opened several avenues for possible new ap- plications in spintronics. Among these materials, CrSBr has sparked interest due to its relatively high Curie temperature, highly anisotropic
lattice structure, and high structural stability. These properties ran along others shared by any atomically thin material such as its outstanding defor- mation capacity and a strong optical response dominated by excitonic effects. The combination of these properties provides a fairly uncharted playground where to explore the interplay between magnetism and optical excitations. Here, we focus our
attention on the theoretical optical response of CrSBr under several distinct strain configurations, analyzing the resulting changes to both the excitonic peaks and overall shape of the diagonal components of the linear conductivity tensor.
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All authors Maurício F. C. Martins Quintela, Guilherme J. Inacio, Miguel Sá, Giovanni Cistaro, Alberto M. Ruiz, José J. Baldoví, Juan J. Palacios, Antonio Picón