Mesoscale and Nanoscale Physics · Cross-listed from physics.app-ph
Supercell-enabled inverse design of boundary-state dispersion for group-velocity control in pseudomagnetic phononic crystals
Hua-Yang Chen, Nan-Xin Yu, Zhen-Hui Qin et al. (+2 more)
Topological boundary states offer a platform for guided-wave propagation within bulk bandgaps. Their propagation characteristics depend not only on the spectral extent of the states but also on their dispersion within the operating bandwidth. A nearly linear dispersion provides more uniform group velocity across frequency, whereas a reduced slope enables slow-wave propagation. Despite advances in inverse design of prescribed dispersion relations and topological dispersion tuning, application-oriented characteristics of boundary-state dispersion have rarely been direct inverse-design objectives. Here, we develop a supercell-enabled, surrogate-assisted framework for the inverse design of boundary-state dispersion in a phononic
crystal with pseudomagnetic fields. Area-preserving anisotropic deformation shifts the local Dirac points, and independent variation of 21 rows within the supercell provides distributed control over the boundary-state branch. A constraint-preserving surrogate reconstructs the dispersion from an initial frequency and positive frequency increments, with first- and second-difference losses introduced to capture local slope and
curvature. Coupled with a genetic
algorithm, the framework targets two prescribed-bandwidth design tasks: highly linear dispersion and slow-wave dispersion. For the former, finite-element verification yields relative group-velocity variations of 0.142% to 1.183% over prescribed bandwidths of 4% to 6%. For slow-wave designs, mean group velocities of 190 to 385 m/s are obtained over bandwidths of 0.2% to 0.8% while satisfying a 5% group-velocity variation limit. These results establish boundary-state dispersion as a direct inverse-design target beyond conventional bandwidth optimization, opening a flexible route to group-velocity control through application-oriented dispersion engineering over prescribed relative bandwidths.
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All authors Hua-Yang Chen, Nan-Xin Yu, Zhen-Hui Qin, Yan-Feng Chen, Si-Yuan Yu
Mesoscale and Nanoscale Physics
Energy levels of screened charged impurity in gapped graphene under magnetic field
Andrii Iurov and V.P. Gusynin
In this paper, we present a comprehensive theoretical study of the electronic states in gapped
graphene in the presence of a charge impurity and a
magnetic field. We focus on the impurity-induced modification of the Landau levels under the influence of an attractive or repulsive Coulomb potential. Since analytical solutions of the Dirac equation are not available in this case, the study is carried out using the Wentzel-Kramers-Brillouin (WKB) approach. Special
attention is paid to the screening of the Coulomb potential in the presence of metallic gates situated at some distances from
graphene sheet, as is commonly the case in experiments. Using both analytical and numerical methods, we determine the energy spectrum as a function of the
magnetic field strength and impurity charge for screened and unscreened Coulomb potentials. Our results reveal a significant dependence of the energy levels for sample-to-gate distances of less than 50 nm.
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Mesoscale and Nanoscale Physics · Cross-listed from gr-qc
Mathematical framework for simulation of non-perturbative cavity optomechanics with plate-like dielectrics
Andrew Laeuger and Nancy Aggarwal
Cavity optomechanical models typically treat a sensor either as a perturbative polarizable object in a pre-existing optical field, or solve the field at a fixed
equilibrium and linearize in a fixed optical-mode basis. Neither self-consistently determines the spatially resolved cavity field, the optical force, the mechanical
equilibrium, and the back-action when a finite-thickness dielectric plate intercepts the entire optical mode and restructures the intracavity field. In this companion paper to [1], we develop that treatment by extending the
vacuum two-
photon formalism to finite-thickness planar dielectrics, incorporating their Fresnel reflection, internal propagation, optical forces, and mechanical back-action directly into the field equations. We derive the carrier and sideband transfer functions needed to describe the coupled optical-mechanical system, including optomechanical cooling and the response to external perturbations. The result is a systematic starting point for calculating detector response and noise budgets for cavity experiments with intracavity dielectrics, including gravitational wave detectors deploying levitated sensors.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Imaging the topological sign of a Dirac mass with spin-polarized tunneling
Payman Kazemikhah, Ruolun Zhang, Byunghoon Kim et al. (+5 more)
A Dirac mass is characterized not only by its magnitude but also by its sign, which influences the Berry
curvature, Hall response, and the propagation direction of chiral boundary modes. However, local spectroscopy of
magnetic topological surfaces has so far accessed only the gap magnitude $|M|$. Here we show how the topological sign of $M$ can be determined locally. We first establish the sign information that
spin-resolved tunneling can access and the reference required to obtain an absolute Hall sign. Although
spin–orbital
entanglement generally obscures the relation between measured
spin and Dirac pseudospin, crystalline rotation
symmetry alleviates this ambiguity at the band edge. On a $C_3$ axis, an axial tip couples to a fully
spin-polarized state whose tunneling asymmetry directly reveals the sign of the occupied-band Berry
curvature, independent of orbital composition. We further show that the zeroth Landau level provides an independent mass-sign measurement with an unpolarized tip, while opposite domains and their chiral domain-wall modes provide self-consistency checks. These results pave the way for imaging the locations where the topological character changes within a material, rather than merely identifying where a spectral gap appears.
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All authors Payman Kazemikhah, Ruolun Zhang, Byunghoon Kim, Xiangyu Luo, Zachary Ducorsky, Yu-Peng Zhu, Md. Shafayat Hossain, M. Zahid Hasan
Mesoscale and Nanoscale Physics
Turning a superconducting diode into a Feynman ratchet to realize a nanoscale heat engine
Konstantinos Kontogeorgiou, İnanç Adagideli, Géraldine Haack et al. (+1 more)
Feynman's ratchet illustrates how work can be extracted from thermal fluctuations in the presence of two heat baths at different temperatures. While some experimental realizations of the ratchet effect have been studied, most lack miniaturization, which is important for some applications. Here, we propose a physical implementation of Feynman's ratchet based on Josephson junctions exhibiting the superconducting diode effect. This setup functions as a heat engine that generates work solely from a temperature gradient via thermal fluctuations. We analyze its output power and efficiency, and, through the Seebeck coefficient, identify the conditions under which the device operates in reverse, functioning instead as a Peltier cooler.
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All authors Konstantinos Kontogeorgiou, İnanç Adagideli, Géraldine Haack, Fabian Hassler
Mesoscale and Nanoscale Physics
Revealing topological protection through unprotected operations in a Majorana parity qubit
Sebastian Miles, Juan Daniel Torres Luna, Francesco Zatelli et al. (+7 more)
A recent experiment reported coherent parity oscillations between minimal Kitaev chains, demonstrating a Majorana parity
qubit (arXiv:2607.09511). Operations on this
qubit are controlled by coupling two Kitaev chains and are intrinsically unprotected against noise in the coupling strength. Here we show how the exponential protection in the underlying chains can nevertheless be revealed through unprotected
qubit operations. To this end, we develop an analytical theory of quasistatic dephasing for two coupled $N$-site Kitaev chains at the sweet spot. In Rabi experiments, protection can be resolved by adapting the operating point with chain length: depending on the coupling architecture, it appears as an exponentially increasing optimized number of coherent oscillations or as a longer coherence time. Ramsey experiments show an exponentially increasing coherence time, provided the chains can be sufficiently decoupled. Our analytical theory takes into account the non-Gaussian splitting statistics of the Kitaev chains, allowing us to quantitatively predict the scaling with chain length. Moreover, we determine how residual noise and imperfections limit the range of chain lengths over which this scaling can be observed. Our results show how
qubit dynamics can be used to probe Majorana protection in experimentally realistic devices.
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All authors Sebastian Miles, Juan Daniel Torres Luna, Francesco Zatelli, Nick van Loo, Antonio Lombardi, Vincent P. M. Sietses, Florian J. Bennebroek Evertsz', Bart Roovers, Leo P. Kouwenhoven, Michael Wimmer
Mesoscale and Nanoscale Physics
Spatial Engineering of Topological Quantum Matter with Structured Light
Matias Mustonen, Ali G. Moghaddam, Teemu Ojanen et al. (+1 more)
Structured light provides a powerful means of controlling matter while itself exhibiting nontrivial spatial
topology. Here, we show that these spatial structures can be harnessed to locally engineer the topological properties of matter. In a paradigmatic example of a topological
insulator with Dirac surface states driven by an optical skyrmion beam, we show that structured light spatially tailors the effective
Hamiltonian, yielding position-dependent topological gaps and Dirac velocities. The resulting gap modulation can create topological and trivial regions separated by optically defined interfaces, without introducing material boundaries or chemical modifications. We further show that the geometry of these interfaces can be controlled through the spatial structure of the light, in particular its orbital angular momentum. Our results establish structured light as a route to dynamically pattern topological phases and open a broader perspective on the interplay between
topology in light and matter, including the possibility of transferring topological characteristics between the two.
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All authors Matias Mustonen, Ali G. Moghaddam, Teemu Ojanen, Marco Ornigotti
Mesoscale and Nanoscale Physics · Cross-listed from cond-mat.soft
Skyrmion gears: translation-to-rotation conversion of skyrmion clusters along periodic substrates
N. P. Vizarim, C. J. O. Reichhardt and C. Reichhardt
We investigate how the translational motion of a compact skyrmion cluster can be converted into collective rotation through interactions with a periodic obstacle substrate. Using an effective particle model, we consider a seven-skyrmion cluster driven along a one-dimensional array of repulsive obstacle sites. For suitable obstacle spacings and interaction strengths, repeated interactions with the substrate produce coherent clockwise or counterclockwise rotation, giving rise to gear-like cluster dynamics. We characterize these states using the translational velocity, Hall angle, angular velocity, structural deformation, and a dimensionless gear ratio that relates cluster rotation to motion over the substrate periodicity. Dynamical phase diagrams identify rotating, nonrotating, wall-guided, transverse, and deformed regimes. We further show that coherent rotation persists in the overdamped limit, demonstrating that the conversion mechanism does not require an intrinsic Magnus force and may therefore extend to other driven cluster systems, including colloidal assemblies. These results provide a simple route for controlling collective rotation through structured substrates.
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Mesoscale and Nanoscale Physics
Non-volatile Orbital magnetoelectric effect in a two-dimensional electron gas
Yu Chen, Martando Rath, Julien Brehin et al. (+10 more)
Electrical control of orbital magnetism is a central goal of orbitronics. While current-induced orbital polarization has recently been demonstrated in inversion-asymmetric systems, nonvolatile electrical control of an
equilibrium orbital moment has remained elusive. Here, using x-ray absorption spectroscopy with in situ electric-field control of the FE polarization, we demonstrate non-volatile switching of the
equilibrium orbital magnetization of the oxide q2DEGs formed at the LaAlO$_3$/EuTiO$_3$/Ca-STO (001) interface. X-ray linear dichroism reveals a reversible modulation, driven by the FE-polarization direction, of the Ti-3$d$
crystal-field splitting and orbital occupancy, establishing a ferroelectric-like metallic state. X-ray
magnetic circular dichroism shows a polarization-controlled switching of the Eu$^{2+}$ orbital
magnetic moment induced by the orbital magnetization of the q2DEG projected onto Eu-5$d$ states and detected at the Eu-$M_{4,5}$ edge through Eu-5$d$/Eu-4$f$ hybridization in the inversion-
symmetry-broken interface. These results provide spectroscopic evidence of ferroelectric control of orbital magnetism in an oxide q2DEG.
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All authors Yu Chen, Martando Rath, Julien Brehin, Cinthia Piamonteze, Daniele Preziosi, Payal Wadhwa, Alessio Filippetti, Yuri Fukaya, Mario Cuoco, Filomena Forte, Daniela Stornaiuolo, Manuel Bibes, Marco Salluzzo
Mesoscale and Nanoscale Physics
Bifurcation Structure of Double Hysteresis and Isolated Branches in a Parametric Duffing Nanoresonator
Dingda Zhang, Maria Kallergi, Chanyoung So et al. (+2 more)
Direct and parametric driving together generate nonlinear response structures beyond conventional Duffing hysteresis, including multiple switching regions and isolated branches. Understanding how these structures are connected requires identifying the bifurcations that reorganize the response as the parametric excitation is varied. At a phase difference of 45 degrees between the direct and parametric excitations, we experimentally and analytically determine how the steady-state response changes as the parametric excitation is increased. A single resonance peak first splits into two while the response remains single valued. Two successive cusp bifurcations then create two saddle-node pairs and establish a double-hysteretic response. At the parametric-instability threshold, one saddle node of each pair is displaced towards unbounded amplitude and detuning, and an isolated-branch structure emerges above threshold. A parametric representation of the steady state distinguishes amplitude extrema from genuine saddle-node bifurcations and provides analytical conditions for these changes. Measurements on a dielectrically actuated pre-stressed SiN nanostring reproduce the predicted response and associated switching behavior. These results establish the bifurcation pathway connecting the different response structures at this phase configuration, providing a systematic basis for controlling multistability and switching in parametrically driven nonlinear resonators.
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All authors Dingda Zhang, Maria Kallergi, Chanyoung So, Eva M. Weig, Ahmed A. Barakat
Mesoscale and Nanoscale Physics
Transport Determines Spectral Distance in Mesoscopic Thermodynamics
Giorgio Sonnino
We derive a distance between thermodynamic states from a positive Hermitian transport tensor within a mesoscopic canonical model. An exact first-order factorization of the
evolution generator gives a commutator norm and the metric $G=2g^{-1}$, where $g$ denotes the symmetric transport tensor. Gradients of the antisymmetric tensor can change the
evolution, but they leave this distance unchanged. The construction allows coordinate-dependent coefficients. For constant Onsager coefficients, a Clifford representation gives the same metric. In a two-channel thermoelectric system, the ratio of normalized principal distances is $\sqrt{1+ZT}+\sqrt{ZT}$. Transport coupling thus fixes the anisotropy of this metric. The construction requires neither an independent metric nor a physical
spin variable.
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Mesoscale and Nanoscale Physics
Emergent Spinorial Structure in Mesoscopic Irreversible Thermodynamics
Giorgio Sonnino
We reconstruct a geometry of thermodynamic coordinates from transport coefficients within a mesoscopic canonical model. Self-adjoint flux observables determine a compatible
evolution generator containing symmetric and antisymmetric transport coefficients. When the Hermitian transport tensor is positive, an exact graded first-order factorization reproduces this generator on its scalar sector. Its commutators define a spectral distance whose metric depends only on the symmetric tensor. Gradients of the antisymmetric tensor can change the
evolution while leaving the metric unchanged. The construction allows coordinate-dependent coefficients. In the constant Onsager regime, a Clifford representation gives the same distance and an
algebra fixed by the transport
matrix. Published transport data for a $\mathrm{Bi_2Te_3}$ film give a principal-distance ratio of approximately $2.12$ in normalized coordinates at $ZT\simeq0.68$. We also examine a separate quadratic
entropy-production observable and distinguish its discrete spectrum from the spectrum of the
evolution generator. The spinorial representation adds no physical
spin degrees of freedom.
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Mesoscale and Nanoscale Physics
1/f frequency-noise reduction in nanomechanical resonators by dissipation dilution
Kostas Kanellopulos and Silvan Schmid
The frequency noise of a resonant nanomechanical sensor is well understood down to its thermomechanical limit, but the longest useful averaging time is set by a flicker, or $1/f$, frequency-noise floor whose origin has remained unknown. We show that this floor is the thermal noise of the tension. By the fluctuation-dissipation
theorem, the tension of a resonator with fixed ends fluctuates by an amount set by the loss angle of its material; for structural damping, these fluctuations produce $1/f$ frequency noise with a flicker coefficient $h_{-1}=E k_{\mathrm{B}} T/(2\pi V\sigma_0^2 Q_{\mathrm{el}})$, with $Q_{\mathrm{el}}$ the intrinsic loss under elongation, that contains no free parameter and is diluted by the tensile stress $\sigma_0$ in the same way as damping is in dissipation dilution. Silicon nitride strings and membranes from 30 to 340~nm thickness follow the predicted volume scaling, the predicted $\sigma_0^{-2}$ dilution across resonators and within stress-engineered strings, and the predicted thickness dependence, which places noise-active two-level systems in the volume and at the surfaces of the resonators, all at the absolute level set by the independently measured intrinsic loss. The same relation accounts for published data between 78 and 296~K; below 78~K, the loss measured at the resonance no longer represents the loss probed by the noise, marking the limit of the structural-damping assumption. Dissipation dilution therefore lowers the $1/f$ floor, and the longest useful integration time of a resonant sensor is set by its prestress, volume, temperature, and intrinsic loss angle.
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Mesoscale and Nanoscale Physics
Nontrivial topological properties from the cooperation of static perturbations and Floquet fields in type-II semi-Dirac semimetals
Wen-Hao Bian and Jing Wang
In this work, we present a comprehensive theoretical study for the topological and anomalous transport properties of type-II SDSMs under three scenarios, i.e., static
symmetry-breaking perturbations, periodic Floquet driving by two-frequency orthogonally polarized light (TFOPL), and their cooperative effects in the hybrid scenario. We first show that a static mass $m_z$ opens a bulk gap and drives the system into a Chern
insulator with Chern number $C^{\rm per}=\pm 2\,{\rm sgn}(m_z)$. In comparison, TFOPL alone only shifts the positions of Dirac points and cannot open a full gap. Nevertheless, it produces a Berry
curvature odd in the $x$-direction, yielding a finite Berry
curvature dipole (BCD) along $x$ proportional to the sine of the initial phase, while the $y$-component vanishes. The hybrid scenario, by contrast, exhibits a remarkably rich phenomenology. Specifically, its gap-closure criterion becomes cubic and thus admits up to three real roots when the effective parameter along the $x$-direction is negative, thereby producing multiple light-tunable gap-closing points and a series of topological phase transitions. In particular, the BCD exhibits a double-peak structure with strong enhancement near gap-closing
manifolds and synchronized sign reversal of the full vector under external tuning. We further analyze the anomalous Hall conductivity (AHC), anomalous Nernst conductivity (ANC), and anomalous thermal Hall conductivity (ATHC). The AHC and ATHC exhibit quantized plateaus that serve as signatures of Chern-
insulator phases, while the ANC, being a Fermi-surface probe, provides complementary local information and can identify light-induced gaps even when global topological invariants remain unchanged. Taken together, these results offer useful insights into the topological properties of 2D type-II SDSMs and related systems.
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Mesoscale and Nanoscale Physics
Admittance extraction of quantum dot arrays for charge sensing
Conor Power, Mathieu Moras, Andrii Sokolov et al. (+2 more)
This work demonstrates admittance extraction of
quantum dot arrays using a rate equation frame- work matching experimental reflectometry measurements. Using a semiclassical rate equation, we consider a perturbation of the source/drain chemical potential to model reflectometry readout in a
quantum dot array. This is a time-dependent extension of the rate equation which has been employed in literature for pumped arrays of
quantum dots and capacitance extractions. Here we extend this to a double
quantum dot for admittance extraction. The simulations are calibrated us- ing Fermi-Hubbard parameters extracted from experimental data, which it is then shown to closely approximate to.
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All authors Conor Power, Mathieu Moras, Andrii Sokolov, Robert Bogdan Staszewski, Elena Blokhina
Mesoscale and Nanoscale Physics
Probing quantum nonlinear phononics in multilayer graphene with time-resolved Raman scattering
Jakob Dolgner, Michael Rübhausen and Dirk Manske
Coherently driven
phonons are conventionally described classically. Nonlinear
phonon-
phonon interactions, however, allow an infrared drive to reshape the fluctuation spectrum and generate substantial nonthermal enhancement of
phonon fluctuations, motivating a description beyond the coherent displacement alone. We
benchmark classical and semiclassical approximations against the full
quantum theory and find that the semiclassical treatment substantially improves agreement with the
quantum dynamics. We propose nonequilibrium spontaneous Raman scattering as a sensitive probe of these effects and apply our framework to recent experiments suggesting
quantum nonlinear phononics involving the $\mathrm{E}_{1u}$ and $\mathrm{E}_{2g}$ modes in multilayer
graphene. At very strong pump fields, driving the $\mathrm{E}_{1u}$ mode significantly modifies the $\mathrm{E}_{2g}$ Raman spectrum; however, reproducing the reported response at experimental field strengths requires accounting for pump-induced Raman
matrix element dynamics or alternative energy pathways into the $\mathrm{E}_{2g}$ mode. Our findings extend nonlinear phononics beyond average atomic displacements to the dynamics of
lattice fluctuations, highlighting the interplay between coherent motion and
quantum correlations in driven materials.
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Mesoscale and Nanoscale Physics
Emergence of Nonlocal Hydrodynamics in Many-Body Radiative Heat Transport
Mauricio Gomez Viloria, Florian Herz, Riccardo Messina et al. (+1 more)
We develop a nonlocal hydrodynamic theory of radiative heat transport in many-body systems by coarse graining their microscopic electrodynamic interactions. Long-range radiative exchange naturally generates a spatially nonlocal constitutive relation in which the heat current at a given position depends on temperature gradients over an extended region, while energy conservation retains its local conservative form.
Fourier transport emerges as a controlled long-wavelength limit when the interaction kernel has a finite second spatial moment. When this moment fails to converge, spatial nonlocality survives coarse graining and gives rise to non-
Fourier transport. The resulting framework establishes a systematic bridge between discrete many-body fluctuational electrodynamics and a continuous description of radiative heat transport.
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All authors Mauricio Gomez Viloria, Florian Herz, Riccardo Messina, Philippe Ben-Abdallah
Mesoscale and Nanoscale Physics · Cross-listed from cond-mat.supr-con
Molecule-intercalated van der Waals Josephson junctions uncover complex multiband superconductivity
Daniel Margineda, David Caldevilla-Asenjo, Covadonga Álvarez-García et al. (+6 more)
Intercalation of molecular species provides a route to tailor the electronic structure in van der Waals
superconductors, yet intercalated compounds have rarely been integrated into phase-sensitive
quantum devices. Here, we realize hybrid molecular Josephson junctions based on TaS2/NbSe2
heterostructures. Selective intercalation of the TaS2 electrode induces monolayer-like Ising superconductivity, while the junctions exhibit asymmetric Fraunhofer interference, field-induced and spontaneous Josephson diode effects. The zero-field diode disappears upon reversing the electrode stacking and re-emerges after intercalating the lower NbSe2 electrode. These findings indicate that the hybrid superconducting electrode hosts unconventional superconductivity underlying the nonreciprocal transport, while molecular intercalation acts as a tuning knob for its internal phase structure. This behavior is consistent with a time-reversal-
symmetry-breaking multiband superconducting state characterized by a nontrivial relative phase between superconducting condensates. Our results establish hybrid molecular Josephson junctions as a
quantum-device platform for phase-sensitive investigation and integration of molecularly engineered
superconductors, opening opportunities to uncover and engineer unconventional superconducting phases.
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All authors Daniel Margineda, David Caldevilla-Asenjo, Covadonga Álvarez-García, Daniel Tezze, Raul Arenal, Maxim Ilyn, Celia Rogero, Luis E. Hueso, Marco Gobbi