Statistical Mechanics
Wasserstein-2 gradient flows and the geometry of entropy production in classical and quantum stochastic thermodynamics
Olga Movilla Miangolarra, Ralph Sabbagh and Artemy Kolchinsky
The second law does more than set the direction of thermodynamic
evolution: it endows nonequilibrium transformations with an underlying geometry. In this work, we provide a unified
geometric description of
entropy production in classical and
quantum thermodynamics based on Wasserstein-2 structures arising from gradient flows of free energy. We review how relaxation to
equilibrium, in overdamped
diffusions, discrete detailed-balanced Markov chains, and dissipative Lindblad dynamics, can be formulated as a gradient flow on the space of states. The associated Wasserstein-2 distance bounds
entropy production, yielding a finite-time refinement of the second law. We extend this framework beyond purely dissipative dynamics by introducing generalized Wasserstein-2 metrics that incorporate conservative (
Hamiltonian) dynamics in both classical inertial systems and open
quantum systems, yielding intrinsic distances that exactly characterize minimal
entropy production under fixed dissipative mobilities. We establish equivalence bounds between purely dissipative and
Hamiltonian-dissipative geometries, explicitly quantifying how inertial or coherent dynamics can reduce dissipation. Finally, when restricted to
equilibrium distributions, we recover the thermodynamic length of linear response-including the
quantum thermodynamic length-thereby linking optimal transport, thermodynamic length, and counterdiabatic protocols within a single
geometric framework. All in all, our results extend the Riemannian program of thermodynamics further from
equilibrium and provide a
geometric foundation for optimal protocols beyond the overdamped setting.
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Strongly Correlated Electrons
Magnon bandstructure and topology in a periodically deformed Kagome lattice with DM interaction
Mohammed Abdullah Hammadi, Mohammed Salman Alsadah, Husam Abdulmajeed Noorwli et al. (+2 more)
We study the band structure and
topology of
magnons for a Heisenberg model with DM interaction on a deformed Kagome
lattice. For simplicity, we focus on a periodically deformed
lattice with hexagonal
symmetry and an enlarged unit
cell. This enlarged unit
cell gives rise to a richer band structure than in the undeformed case. Analyzing band
topology, there is a distinction between the topologically trivial case with anti-
ferromagnetic coupling and the topologically rich case with
ferromagnetic coupling. In the anti-
ferromagnetic case, a
spin-space
symmetry, also present in the classical ground state, enforces these topologically trivial states. In the
ferromagnetic case, this
symmetry is spontaneously broken by the classical ground state. Consequently, the band structure also hosts rich topological features. Specifically, we observe many topological transitions and bands with Chern numbers ranging from $+2$ to $-2$, which makes the system richer than in the undeformed case. This emergent rich topological structure demonstrates that deformed magnets can host new and exciting physics.
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All authors Mohammed Abdullah Hammadi, Mohammed Salman Alsadah, Husam Abdulmajeed Noorwli, Hocine Bahlouli, Michael Vogl
Materials Science
A Visible-Frequency Excitonic Reststrahlen Band in (PEA)$_2$PbI$_4$ Slabs
Michael Pfeufer, Patrick Grenzer, Friedrich Schöppler et al. (+1 more)
Layered halide perovskites host exceptionally strong
excitons, whose optical signatures are usually interpreted as absorptive resonances on a smooth dielectric background. Strong
excitons, however, can also reshape the dielectric response itself and drive the real permittivity negative, opening a reflective band: the visible, excitonic analogue of an infrared Reststrahlen band. Whether bare (PEA)$_2$PbI$_4$ slabs reach this regime has remained unclear. Here we show that low-temperature transmission of (PEA)$_2$PbI$_4$ slabs, driven by the intralayer-
exciton manifold, evolves with increasing thickness from an excitonic dip into a broad near-zero-transmission interval with compressed Fabry-Pérot-like fringes. Transfer-
matrix analysis with an effective Lorentz-oscillator dielectric response reproduces this crossover, reconstructs a finite negative-Re($\varepsilon$) window, and implies near-ultrastrong
exciton-
photon coupling. Calculated field maps show suppressed in-plane field penetration within this interval and a driven longitudinal response near the high-energy ($\varepsilon=0$) edge. These results identify (PEA)$_2$PbI$_4$ slabs as a cavity-free visible-frequency excitonic Reststrahlen material.
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All authors Michael Pfeufer, Patrick Grenzer, Friedrich Schöppler, Tobias Hertel
Mesoscale and Nanoscale Physics · Cross-listed from physics.class-ph
Unified Theory of Quartz Tuning Fork Resonators
Hankyul Koh and Wonho Jhe
Quartz tuning forks, functioning as electrically driven piezoelectric resonators, have long served as exceptionally stable and widely adopted timing references in diverse domains of research and industry. Yet, experimentally measured electrical resonance spectra often exhibit resonance evolutions that remain unexplained within existing theoretical descriptions. Here we develop a unified continuum electromechanical modal framework that integrates piezoelectric electrodynamics, variational structural dynamics, and
symmetry-selected electromechanical observability. Our theory shows quantitative agreement with experimental results, demonstrating that electrical observability emerges not from the underlying mechanical eigenmodes alone. The resulting framework unifies conventional coupled-oscillator, equivalent-
circuit, and continuum descriptions within a single first-principles theory and provides a rigorous basis for precision electromechanical characterization.
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Materials Science
Manifold Diffusion for Structure Generation of Transition Metal Complexes
Luca Schaufelberger and Kjell Jorner
Transition metal complexes are central to catalysis, drug design, and materials science, with relevant properties strongly sensitive to their three-dimensional geometry. However, the electronic diversity and unconventional bonding environments of transition metal complexes pose a major challenge for accurate structure generation. In this work, we introduce TMCgen, a
manifold diffusion machine learning model that efficiently and accurately generates geometries of transition metal complexes. By formulating the
diffusion process over the metal-ligand coordination angles, combined with torsional and rotational
diffusion of the ligands, TMCgen focuses on the key
geometric degrees of freedom of transition metal complexes. TMCgen shows strong performance in generating accurate coordination environments on a diverse set of experimentally derived bioinorganic and organometallic complexes while requiring only few inference steps, enabling efficient generation. Our results demonstrate the potential of
manifold-based generative modeling for data-efficient geometry generation, paving the way for property-conditioned design of transition metal complexes.
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Materials Science
Impact of Disorder Dynamics and Multi-Domain Kinetics on the Sliding Ferroelectricity of CVD-Grown 3R-WSe2 Bilayers
Sourav Paul, Prasenjit Ghosh, Krishna Prasad Maity et al. (+9 more)
Sliding ferroelectricity in van der Waals (vdW) layered systems has emerged as a promising route toward non-volatile nanoscale devices, where interlayer displacement in non-centrosymmetric
bilayers generates an out-of-plane polarization. In particular, 3R-stacked
bilayer transition metal dichalcogenides (TMDs) grown via chemical vapor deposition (CVD) have been shown to host such polarization due to broken inversion
symmetry. However, a detailed investigation of the 2D ferroelectric (FE) properties of CVD-grown 2D films, particularly the role of intrinsic disorder, such as structural defects and domain structure, remains poorly understood. Here, we investigate the FE switching characteristics of CVD-grown 3R-stacked WSe2 using a
graphene-based ferroelectric field-effect transistor (
graphene-FE-FET) architecture, where
graphene serves as a highly sensitive probe of induced charge modulation due to polarization switching of FEs. We show that the growth-induced structural disorder significantly impacts polarization switching, while multi-domain kinetics governs the
evolution of the FE response. These findings provide important insights into the design and optimization of FE devices based on vdW materials.
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All authors Sourav Paul, Prasenjit Ghosh, Krishna Prasad Maity, Vineet Pandey, Abhijith M.B., Premananda Chatterjee, Kenji Watanabe, Takashi Taniguchi, Nicholas R. Glavin, Ajit K. Roy, Atindra Nath Pal, Vidya Kochat
Soft Condensed Matter · Cross-listed from math.NA
Tensor gradient flow with quasi-entropy for smectic liquid crystals and discretizations keeping coupled physical constraints
Jie Xu and Xiaomei Yao
A gradient flow for the concentration and a $2\times 2$ tensor is constructed to describe smectic
liquid crystals. The free energy consists of the
entropy term and interaction term involving squared second order spatial derivatives. The
entropy term incorporates the concentration in the quasi-
entropy originally proposed for the tensor only, which is a strictly convex and lower semicontinuous function imposing coupled constraints between the concentration and the tensor. An
evolution equation for the boundary normal derivative of the concentration is proposed in addition to the equations for the concentration and the tensor, giving an energy dissipation system. Numerical schemes are designed with emphases on using the
entropy term to keep the coupled constraints, and the discretization of the boundary normal derivatives satisfying summation by parts. Existence, uniqueness, energy dissipation and error estimates are established. Numerical results indicate the efficiency and robustness of the scheme. Configurations of defects different from other layer structures are observed.
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Strongly Correlated Electrons
Supersymmetric quantum criticality with discrete symmetry
Teng-Yue Wang and Shuai Yin
Supersymmetry, originally proposed in high-energy physics, can emerge as a remarkable low-energy structure in condensed matter systems. While emergent supersymmetry at
quantum critical points is widely discussed in models with continuous
symmetries, real materials are constrained by microscopic discrete
symmetries. To address this, we investigate (2+1)-dimensional Gross-Neveu-Yukawa theories coupling Dirac
fermions to a complex order parameter with discrete $Z_n$ anisotropy. Using the functional renormalization group, we find that for $n>3$, the anisotropic perturbations are irrelevant at the fixed point, yielding a $\mathcal{N}=2$ Wess-Zumino supersymmetric critical point. In the ordered phase, this dangerously irrelevant anisotropy gives rise to a second characteristic length scale, $\xi'$, alongside the usual correlation length, $\xi$. By tracking mass thresholds along
symmetry-broken renormalization group trajectories, we extract the exponents $\nu'$ and $\nu$ without imposing prior scaling assumptions. For the $Z_4$, $Z_5$, and $Z_6$ models, our results support the scaling relation $\nu'/\nu = 1+|y_n|/p$ with $p=2$ in the isotropic framework used here.
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Soft Condensed Matter
Sliding contact creates universal self-affine fractal surfaces
Ruibin Xu, Haohao Ren, Adriane Clerc et al. (+4 more)
Surface roughness evolves during sliding, a process known as run-in, and the resulting topography controls friction, leakage, and failure from machines to geological faults. Yet the physical rule selecting this state remains unclear. We show that metals, rocks, and glasses develop universal self-similar roughness at short wavelengths, while retaining a material-dependent roll-off. A two-process model explains this behavior: junction formation and rupture drive universal roughening, whereas larger-scale deformation and/or fracture limit its growth.
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All authors Ruibin Xu, Haohao Ren, Adriane Clerc, Guilhem Mollon, Wenbo Sheng, Feng Zhou, B.N.J. Persson
Mesoscale and Nanoscale Physics
Non-Hermiticity-induced chirality imbalance of Weyl Landau levels
Sachin Vaidya, Alaa Bayazeed, André Grossi Fonseca et al. (+3 more)
Weyl semimetals obey a global chirality constraint: the net
chiral topological charge and any associated
chiral spectral flow must vanish, as required by the Nielsen-Ninomiya
theorem. Under
magnetic fields, this constraint manifests through counter-propagating zeroth Landau levels associated with Weyl nodes of opposite chirality. Here, we experimentally demonstrate how non-Hermiticity can reshape this balance in a synthetic photonic Weyl semimetal. Using engineered gauge fields in one-dimensional multilayer structures, we realize both homogeneous and axial
magnetic fields and directly probe the resulting Landau-level spectra. While a homogeneous field produces the expected chirality-balanced zeroth Landau levels, an axial field spatially separates the compensating
chiral channels: co-propagating bulk pseudo-Landau levels carry one chirality, whereas the opposite chirality resides in boundary-localized surface states. We show that radiative boundary loss selectively suppresses these surface states, removing them from the long-lived observable spectrum and producing an experimentally accessible chirality imbalance. By reducing boundary loss, we recover the hidden
chiral channel and reveal its surface-state origin. These results show that non-Hermiticity, present naturally in photonics, can control and relax fundamental chirality constraints in topological systems, enabling access to otherwise forbidden spectral responses.
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All authors Sachin Vaidya, Alaa Bayazeed, André Grossi Fonseca, Adolfo G. Grushin, Marin Soljačić, Christina Jörg
Soft Condensed Matter
Semiflexible Ring Polymers on Active Motor Beds: Nonequilibrium Dynamics and Conformations
Sandip Roy, Abhishek Chaudhuri and Anil Kumar Dasanna
A semiflexible ring
polymer on a motor-
protein bed exhibits activity- and processivity-dependent rotational and conformational dynamics that are not captured by linear-chain behavior. Using coarse-grained Langevin simulations with bending elasticity, excluded-volume interactions, and
stochastic motor attachment, stepping, and detachment, we vary activity (Peclet number), motor processivity, and chain stiffness to map the nonequilibrium response. The mean-squared displacement shows crossover dynamics, with semiflexible rings displaying subdiffusive-to-diffusive behavior at low activity and an intermediate ballistic regime at higher activity, while increasing flexibility shifts the short-time response toward a Rouse-like limit. Diameter autocorrelations exhibit damped oscillations associated with coherent rotation; the rotational frequency increases with activity and processivity, whereas the decorrelation time is non-monotonic at high processivity.
Fourier mode analysis identifies competition between the radius (k=0) and
elliptic (k=2) modes as the origin of the non-monotonic asphericity.
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Mesoscale and Nanoscale Physics
Noncollinear spin textures and 90{\deg} domain walls in twisted XY magnets
Guanghui Cheng, Shiva T. Konakanchi, Andres E. Llacsahuanga Allcca et al. (+8 more)
Twisted moiré magnets are promising in exploring noncollinear
magnetic phases, yet current experimental studies have been restricted to uniaxial magnets, limiting the accessible phase space. Here, we demonstrate noncollinear moiré magnetism based on XY magnet CrCl3. The tunneling magnetoconductance of twisted CrCl3 exhibits multiple field-driven transitions in small-twist-angle devices, attributed to the coexisting
antiferromagnetic and
ferromagnetic domains with distinct susceptibilities. The inferred
spin configuration depends on the layer number, reflecting the interlayer coupling strength between twisted layers. This moiré magnetism is remarkably robust, persisting up to twisted double nine-layer stacks. Combined with micromagnetic simulations, we identify the ground state as the predicted "twisted-s" phase featuring 90{\deg} domain walls. Finally, we demonstrate voltage control of these noncollinear phases, highlighting the electrically tunable twist-spintronics.
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All authors Guanghui Cheng, Shiva T. Konakanchi, Andres E. Llacsahuanga Allcca, Sanjeev Khare, Nithin Abraham, Yuqing Cao, Hechang Lei, Kenji Watanabe, Takashi Taniguchi, Pramey Upadhyaya, Yong P. Chen
Statistical Mechanics
Non-equilibrium glassy arrest and discontinuous transitions at avoided quantum critical points
J J Pulikkotil
The non-
equilibrium dynamics of an order parameter confined by an external constraint field are investigated within a spatially extended Belitz-Kirkpatrick-Vojta framework. A generic non-monotonic dissipation peak arises at avoided criticality due to the interplay between macroscopic free-energy flattening and microscopic disorder-induced trapping. Near this regime, suppressed deterministic forces enhance activated trapping, leading to an effective violation of the fluctuation-dissipation
theorem and ultimate glassy arrest. At higher fields, the system undergoes a discontinuous phase transition that bypasses this flat free-energy region. These explicit analytical scalings establish a generic mechanism for non-
equilibrium arrest in disordered condensed matter systems.
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Soft Condensed Matter
Velocity Resetting of Inertial Run-and-Tumble Particles in Non-Newtonian Media: Velocity Distribution, Diffusion and First-Passage Time
Subhanker Howlader, Sayantan Mondal and Prasenjit Das
We study the dynamics of an athermal inertial run-and-tumble particle moving through a non-Newtonian medium in $d=1$, where the particle's velocity $v$ is reset to zero at a constant rate $r$. The drag force from the non-Newtonian medium is represented by a nonlinear velocity-dependent function $g(v)$. The run-and-tumble dynamics is modeled by a symmetric dichotomous noise with strength $\Sigma$ and flipping rate $\lambda$. We begin with the Fokker-Planck (FP) equation for the velocity distribution $P(v,t)$ of the particle. In the presence of resetting, however, the FP equation does not yield a closed-form solution even in the steady state. We therefore compute the steady-state velocity distribution $P_s(v)$ directly from particle trajectories and compare it with the numerical solution of the FP equation, finding good agreement between the two approaches. For sufficiently large $r$, $P_s(v)$ shows a cusp-like singularity at $v=0$ and the particles display diffusive motion at long times. The effective
diffusion coefficient $D_{\mathrm{eff}}$ decays as $r^{-2}$ in the large-$r$ regime. These results hold irrespective of the specific form of $g(v)$ and the values of $\lambda$ and $\Sigma$. However, the mean first-passage time exhibits a strong dependence on the nature of the medium as the resetting rate $r$ is varied. In shear-thickening media, there exists an optimal resetting rate that minimizes the time required to reach the target velocity $v_t$. In contrast, no such optimal resetting rate is observed in shear-thinning media.
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Materials Science
Giant Thermal-Conductivity Enhancement from Chiral-Phonon Pseudo-Angular Momentum Conservation
Tingting Wang, Dabao Zha, Hao Chen et al. (+2 more)
Pseudo-angular momentum (PAM) underlies optical selection rules for
chiral phonons, but whether it also constrains thermally populated finite-wave-number
phonon-
phonon scattering has remained unresolved. We show that rotational or screw eigenphase conservation imposes a PAM residue rule on cubic anharmonic vertices, revealing a hidden selection rule for heat transport. In screw-symmetric helical Te, an exact platform, implementing this rule as a projector in first-principles Boltzmann transport leaves spectra and force constants unchanged but removes roughly two thirds of kinematically allowed triplets, suppresses resistive Umklapp relaxation, and enhances
lattice thermal conductivity by a factor of 5.30 at 300 K, remaining above fivefold up to 400 K. A bulk
chiral-
crystal benchmark further shows that explicit eigenphase organization can increase the calculated
lattice thermal conductivity by about 24%, comparable to the reported first-principles underestimation of experiment. These results establish PAM conservation as an anharmonic selection principle for
chiral-
phonon heat transport and as a fundamental principle to guide the prediction and control of thermal conductivity in
chiral crystals and nanoscale phononics.
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All authors Tingting Wang, Dabao Zha, Hao Chen, Jiangbin Gong, Lifa Zhang
Statistical Mechanics · Cross-listed from gr-qc
Relativistic transformation of temperature revisited
Soroor Pouryazdan and Babak Vakili
The relativistic transformation of temperature has long remained controversial, with the classical laws of Planck-Einstein, Ott-Eddington-Moller and Landsberg yielding conflicting results. We reexamine this issue from a relativistic thermodynamic and statistical perspective, starting from the energy-momentum tensor of an isotropic system and defining the effective temperature Teff as that inferred by a moving observer from the transformed energy density. Analyses of a
photon gas, a relativistic ideal gas and an electron gas show that Teff consistently increases with velocity, supporting the Ott-Eddington interpretation while depending on the system's equation of state. These results indicate that temperature is not a Lorentz-invariant scalar but an observer-dependent quantity. A consistent relativistic description emerges when temperature is related to the inverse-temperature four-vector beta, linking operational and invariant viewpoints within a unified thermodynamic framework.
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Materials Science
Synthesis of single-layered fluorographdiyne nanosheets via selective on-surface 2D covalent polymerization
Chen-Hui Shu, Yi Zheng, Tao Lin et al. (+14 more)
Two-dimensional conjugated
polymers (2DCPs) are significant macromolecular materials with intriguing and tunable physicochemical properties that depend on their geometries. Graphdiyne and its derivatives are exemplary 2DCPs featuring sp-sp2 hybridized skeletons. However, achieving single-layered, large-domain/regular graphdiyne and its derivatives on surfaces remains a formidable challenge due to the lack of selective 2D covalent polymerization methods. Here, we report a selective on-surface 2D covalent polymerization method via the combination of cobalt catalysis and coronene templating, achieving the synthesis of single-layered fluorographdiyne nanosheets up to 60*60 nm2 on Au(111) surface. Using scanning probe techniques, we visualize the sequential polymerization process and characterize cobalt-activated coupling intermediates at the atomic level. Experimental and theoretical analyses suggest that strong d-{\pi} coupling between cobalt and alkynyl transforms a robust Csp-Au bond into a weaker Csp2-Au bond, thereby facilitating the demetallization C-C coupling. Besides, the templating effect of coronene suppresses kinetically trapped defects and improves the selectivity of hexagonal-ring formation in the complex 2D covalent polymerization process.
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All authors Chen-Hui Shu, Yi Zheng, Tao Lin, Li-Xia Kang, Zhang Qu, Zhi-Yu Wang, Ying Wang, Zheng-Yang Huang, Qian Liu, Hang Xu, Chong Chen, Yangfan Wu, Longteng Xiao, Mengxi Liu, Xiaohui Qiu, Pei-Nian Liu, Deng-Yuan Li
Mesoscale and Nanoscale Physics
The Uhlmann phase of Higher-Order Topological Insulators at Finite Temperature
Shiyu Chen and Yan He
We have studied the finite-temperature
topology of higher-order topological
insulators (HOTIs) based on the Uhlmann phase, which is a phase angle of the Uhlmann overlap. As an example of HOTIs, the
Hamiltonian of the Benalcazar-Bernevig-Hughes (BBH) model is constructed from Gamma
matrices satisfying the Clifford
algebra. This specific algebraic structure underpins the model's higher-order topological properties, including the quantization of the Uhlmann phase to $0$ or $\pi$. This quantization enables us to treat the abrupt jumps of the Uhlmann phase as an indication of the nontrivial topological phase of the BBH model at finite temperature. From the disappearance of these jumps, we determine the critical temperature at which the topological transition occurs. For a special choice of parameters, the Uhlmann overlap and the critical temperature can be computed analytically.
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Strongly Correlated Electrons
Complexity of tensor network simulation for noisy quantum circuits
Yuguo Shao, Zishuo Zhao, Song Cheng et al. (+1 more)
We aim to rigorously address how local noise affects classical simulability of
quantum dynamics benchmarked by tensor-network methods. Using operator
entanglement entropy (OEE), we prove the following: (1) For single-
qubit depolarizing noise on arbitrary
circuits, tensor networks with $\mathrm{poly}(n)$ bond dimension suffice for fixed absolute
Hilbert-Schmidt error after $\order{1}$ depth, while relative error demands $\order{\log n}$ depth; and this bound is optimal. (2) For single-
qubit depolarizing noise on 1D local
circuits, the existence of whole-trajectory error-bounded
matrix product operator (MPO) of $\mathrm{poly}(n)$ bond dimension at all depths. (3) For general single-
qubit noise in 1D brickwall
circuits, random two-design gates with contraction coefficient $c<1/3$ yield an $\order{1}$ OEE plateau with probability $1-Te^{-\Omega(n)}$, while arbitrary gates with $c<1/48$ give $\order{\log n}$ OEE in the worst case. (4) In higher dimensions, these bounds yield uniform-in-depth $\mathrm{poly}(n)$ average boundary-bond dimensions for projected entangled pair operators~(PEPO) across every cut – under depolarizing noise at either absolute or relative accuracy, and under general noise with strong contraction at absolute accuracy. Our results establish a rigorous connection between certain noise models,
circuit types, and their classical simulability.
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All authors Yuguo Shao, Zishuo Zhao, Song Cheng, Zhengwei Liu
Soft Condensed Matter · Cross-listed from cs.RO
A passive universal grasping mechanism based on an everting shell
Mythra V. S. Balakuntala, Safvan Palathingal and G. K. Ananthasuresh
A passive monolithic compliant grasping mechanism that works based on the eversion of an elastically deformable bistable shell is conceptualized. It comprises grasping arms made of beam segments that work in conjunction with the everting shell. The grasper is capable of picking up a stiff object of any shape up to a maximum size and weight. The bistable shell everts upon contact with the object to enable the grasping arms envelop the object forming an enclosure. The mechanism then stays in that configuration until it is actuated again to turn the shell back to its original configuration and thereby opening the enclosure to release the object. The stiffness of the arms decides the payload of the mechanism. The size of the arms decides the largest object that can be grasped and held. The arms have distributed compliance so that they can conform to the shape of the object without applying undue force on it.
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Strongly Correlated Electrons
Cleavage-History-Dependent Low-Temperature ARPES Spectra of Charge-Ordered EuAl$_4$
Hao Liu, Bo Chen, Chen Zhang et al. (+9 more)
Charge ordering in EuAl$_4$ has been widely discussed in connection with band reconstruction, magnetism, and topological electronic states, yet the microscopic origin of the complex low-temperature ARPES spectra remains unresolved. Here we combine
photon-energy-, temperature-, and cleavage-history-dependent ARPES with first-principles calculations to distinguish intrinsic bulk bands from surface-preparation-dependent spectral weight. Spectra measured on high-temperature-cleaved surfaces, both at 160 K and after cooling to 10 K, are broadly consistent with the calculated three-dimensional bulk electronic structure, whereas low-temperature-cleaved surfaces exhibit additional electron-like bands, replica-like
Fermi-surface contours, and a pronounced $\delta$ band near -0.57 eV that is absent from the calculated bulk bands. The additional features are observed at multiple
photon energies and on multiple independently cleaved surfaces and are selectively suppressed upon warming, while the bulk-derived bands remain comparatively stable. The $\delta$ band does not emerge when the same high-temperature-cleaved surface is cooled through $T_{\rm CDW}$. Comparison with the projected bulk bands and the calculated spectral function of an ideal Eu-terminated surface further associates the additional bands with the surface electronic structure. These results establish a strong cleavage-history dependence of the low-temperature ARPES spectra and provide spectroscopic criteria for separating surface-reconstruction and bulk charge-order contributions in EuAl$_4$.
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All authors Hao Liu, Bo Chen, Chen Zhang, Qi-Yi Wu, Sheng-Tao Cui, Zhe Sun, Zhong-Tuo Fu, Ying Zhou, Yang Luo, Jun Liu, Yu-Xia Duan, Jian-Qiao Meng
Mesoscale and Nanoscale Physics
Individually tunable Si/SiGe quantum dot operating voltages via gate-biased illumination
Jared Benson, Sanghyeok Park, Owen M. Eskandari et al. (+6 more)
Semiconductor quantum dot
qubits often require very different voltages on each gate to bring them to a correct operating point. Here, we present a method by which one can controllably and repeatably alter the nanoscale trapped charge distribution at an
oxide-
semiconductor interface. We demonstrate this method on a Si/SiGe
quantum dot device, and we find that the operating voltages can be controlled and made much more uniform. The method relies on illumination with near-infrared light in the presence of applied gate voltages, and it enables the tuning of the device operating point on a gate-by-gate basis. We present an explanation of the underlying physics using self-consistent Schrödinger-Poisson simulations. As an application of this method, we tune a triple
quantum dot to have uniform and small operating voltages in the (1,1,1) charge configuration. Importantly, we show that shifting the operating voltages in this way does not change the measured charge noise.
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All authors Jared Benson, Sanghyeok Park, Owen M. Eskandari, M. A. Wolfe, Brighton X. Coe, J. P. Dodson, S. N. Coppersmith, Mark Friesen, M. A. Eriksson