Mesoscale and Nanoscale Physics
Quantum-Geometric Bound on Dynamical Instability in Bosonic Systems
A.M. Tishin
Quantum-
geometric speed and dynamical instability are two natural rates for a driven
quantum system, and their relation is unsettled even for exactly solvable dynamics. Here we show that for any multimode quadratic bosonic system referred to the bare-mode
vacuum the Fubini-Study speed v_FS is the Frobenius norm of the symmetric, stretching part of the flow: the rate at which the
vacuum becomes distinguishable from itself measures instantaneous symplectic stretching. That identity turns a classical stability estimate into a
quantum-
geometric bound, lambda_max <= sqrt(2) v_FS, sharp at every mode number and saturated by a resonant pure squeezer. The bound is not invertible: in a detuned parametric amplifier we hold either rate fixed while varying the other.
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Mesoscale and Nanoscale Physics
Layer-Number-Controlled Symmetry Breaking and Surface-State Transport in Rhombohedral Graphene Multilayers
Bosai Lyu, Jian Zheng, Kai Liu et al. (+12 more)
Rhombohedral multilayer
graphene hosts layer-polarized flat bands, providing an intriguing platform for correlated and topological electronic states; however, the role of layer number in governing
symmetry breaking and surface screening remains elusive. Here we prepare rhombohedral
graphene multilayers and systematically conduct electrical transport measurements. We uncover an unconventional layer dependence of phase transitions: the critical displacement field (D$_{c}$) for the layer-antiferromagnetic (LAF)-to-semimetal transitions remains constant across tetralayer to hexalayer
graphene, whereas the D$_{c}$ for semimetal-to-layer-polarized-
insulator (LPI) transition increases with layer number, defying unscreened Coulomb interaction models. In hexalayer
graphene, surface-state-dominated transport emerges, with Landau levels (LLs) and resistive peaks selectively controlled by adjacent gates, a signature of strong interlayer screening absent in thinner stacks. High
magnetic fields reveal valley-layer-locked LLs and dissipative states possibly from interlayer backscattering, highlighting the presence of decoupled surface states. Our findings establish layer number as a key tuning knob for engineering correlated and topological phases in rhombohedral
graphene multilayers.
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All authors Bosai Lyu, Jian Zheng, Kai Liu, Yulu Ren, Size Wu, Yating Sha, Shuhan Liu, Youngju Park, Kenji Watanabe, Takashi Taniguchi, Jinfeng Jia, Zhiwen Shi, Jeil Jung, Weidong Luo, Guorui Chen
Mesoscale and Nanoscale Physics
Large bias-tunable magnetoresistance from spin-dependent interlayer hybridization in van der Waals antiferromagnet CrSBr-based heterostructures
Sadeed Hameed, Aditya Kumar, Chengjie Yu et al. (+5 more)
We explore the large magnetoresistance (MR) in \ce{hBN}/few-layer-
graphene/\ce{CrSBr}/few-layer-
graphene heterostructures and reveal the mechanism behind its non-monotonic bias dependence. Using bias voltage and temperature as independent tuning knobs, we achieve MR up to \SI{350}{\percent} at \SI{20}{K}, characterized by symmetric M-shaped maxima around $\pm 0.5\,\mathrm{V}$. Continuous tuning of the magnetization angle $\theta$ via a hard-axis
magnetic field shows that the barrier band-edge offset varies linearly with $\cos(\theta/2)$, a first-order signature of
spin-dependent interlayer hybridization. This linear relationship rules out the Jullière model and a
spin-filter projection. We conclude that the
magnetic-configuration-dependent band edge, rather than electrode
spin polarization, dictates the large magnetoresistance in \ce{CrSBr} junctions.
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All authors Sadeed Hameed, Aditya Kumar, Chengjie Yu, Aravind P. Balan, Xinran Wang, Lichuan Zhang, Yuriy Mokrousov, Mathias Kläui
Mesoscale and Nanoscale Physics · Cross-listed from cond-mat.mtrl-sci
Strain-controlled magnetism and magnetoelasticity in monolayer NiPS$_3$ and CrPS$_4$
Balázs Nagyfalusi, Alvaro Bermejillo-Seco, Linde de Jong et al. (+5 more)
We develop a first-principles framework for magnetoelastic coupling in two-dimensional magnets based on a strain-dependent Heisenberg model. In this approach, strain derivatives of the exchange interactions provide direct access to magnetostriction and to the
magnetic renormalization of the elastic tensor, establishing a microscopic link between
spin interactions and elastic response. We apply the method to monolayer NiPS$_3$ and CrPS$_4$, which exhibit contrasting magnetoelastic behavior. NiPS$_3$ shows weak and nearly isotropic
spin-
lattice coupling, consistent with a robust zigzag antiferromagnetic ground state. In contrast, CrPS$_4$ displays strong anisotropic coupling, leading to strain-driven transitions between
spin-spiral and ferromagnetic phases and significant changes in the critical temperature and elastic response. Our results demonstrate a general route to quantify magnetoelastic effects in low-dimensional magnets and highlight CrPS$_4$ as a promising platform for strain engineering of
magnetic order.
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All authors Balázs Nagyfalusi, Alvaro Bermejillo-Seco, Linde de Jong, Ritesh Das, Yaroslav M. Blanter, Herre S. J. van der Zant, Amador Garcia-Fuente, and Jaime Ferrer
Mesoscale and Nanoscale Physics · Cross-listed from cond-mat.supr-con
Light induced superconducting diode effect in patterned films
Evan M. Wilson, Hou-Tong Chen and Alexander V. Balatsky
Structured light offers a route to control superconducting transport without permanently modifying the material or applying a static bias. Here we show that structured optical driving can generate a superconducting diode response in patterned superconducting films with asymmetric holes. Using generalized time-dependent Ginzburg Landau simulations, we find that optical driving produces rectified dc photovoltages and zero bias directional supercurrent imbalance in a junction free geometry, with continuous-drive diode efficiencies of order $10^{-3}$ and pulsed efficiencies reaching $10^{-2}$. The response is controlled by both the hole array and the optical mode. Increasing the number of asymmetric holes enhances rectification, reversing circular helicity reverses the diode polarity, and the optical spatial mode strongly modifies the magnitude and polarity of the directional response. Pulsed excitation enhances the zero bias line cut current imbalance to the percent level. For linearly polarized illumination, the asymmetric metacrystal converts the drive into local chiral supercurrent motion, inducing an inverse Faraday effect like mechanism for dynamical time reversal
symmetry breaking. These results establish patterned superconducting films as a viable platform for light-tunable superconducting diode behavior.
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Mesoscale and Nanoscale Physics · Cross-listed from cond-mat.stat-mech
Exact First-Passage Time Response Theory from Steady-State Response
Ruicheng Bao and Shiling Liang
The mean first-passage time (MFPT) provides a universal temporal measure of transport, reaction, search, and switching processes in physical, chemical, and biological systems. Understanding how MFPTs respond to perturbations is therefore crucial for prediction and control, yet a systematic theory has been lacking. We establish a compact theoretical framework for linear and nonlinear MFPT response in continuous-time Markov processes. The key tool is an exact correspondence that maps the intrinsically transient response of MFPTs onto the steady-state response of an auxiliary system. This correspondence yields exact and universal response relations for MFPTs between arbitrary state pairs, expressed entirely in terms of unperturbed MFPTs and steady-state probabilities. We then obtain a factorized physical decomposition of the MFPT response into linear upstream, linear downstream, and nonlinear contributions. Further corollaries include response-curve inference rules, fundamental bounds on MFPT responses, analytical expressions for higher-order responses of MFPTs and steady-state probabilities, and multi-rate response formulas. Additionally, our result offers computational advantages in calculating both MFPTs and steady-state distributions. Finally, a biologically motivated folding network is analyzed, and a recently reported paradox on MFPT is clarified.
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Mesoscale and Nanoscale Physics
Floquet Engineering of Topological Phases and Magneto-Optical Response in a Driven $d$-wave Altermagnet
Muzamil Shah
We study how Floquet driving with linearly polarized light controls the
topology and magneto-optical response of a two-dimensional (2D) $d$-wave altermagnet. In the absence of linearly polarized optical field and under
spin conservation, we find that the system hosts a
spin-Chern (a
quantum-
spin-Hall analog) phase with Chern numbers of opposite sign in the two
spin sectors. The irradiated optical field breaks the $C_{4z}\mathcal{T}$ crystalline antiunitary
symmetry between the
spin sectors.
Symmetry breaking originates from polarization-dependent Peierls phases, which renormalize hopping anisotropically along the two axes. The resulting
spin-selective gap closures produce intermediate Chern-insulating phases with $C=\pm1$. The drive amplitude $A_0$ determines the inversion thresholds, while rotating the polarization by $\pi/2$ swaps the
spin sectors and reverses the Chern number. Using the Kubo formalism, we compute the frequency-dependent longitudinal and Hall conductivities and derive the corresponding Faraday and Kerr rotations for a free-standing conducting sheet. The longitudinal response tracks the Floquet-renormalized interband thresholds, whereas the optical Hall response, together with the sign of the magneto-optical rotations, distinguishes the two opposite Berry-
curvature chiralities. Sizable Kerr angles occur only within narrow resonant windows and should be interpreted together with the reflected intensity and Kerr ellipticity. These results identify linearly polarized light as a
symmetry-selective handle for
spin-resolved band inversion, Chern-number switching, and contact-free optical detection in $d$-wave altermagnets.
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Mesoscale and Nanoscale Physics · Cross-listed from cond-mat.str-el
Floquet Green's functions for lattice electrons driven by Gaussian quantum light
Atsushi Ono
We formulate Floquet Green's functions for noninteracting single-band
lattice electrons driven by a reservoir-stabilized single-mode Gaussian
quantum light source. The source is prescribed externally and is not updated by the many-electron polarization, while an active electronic probe still conditions the source
evolution through the Peierls coupling. The two time arguments of a Green's function share one source history: the lesser and greater components are obtained by convolving a shared-history four-endpoint kernel with the continuous bath kernels before the final source trace, while the bath canonical anticommutation relation yields an equal-time covariance that seeds the retarded and advanced one-leg propagations. The Peierls coupling is treated nonperturbatively within the prescribed-source model, and classical Floquet theory is recovered in the appropriate limit. Numerical calculations on a minimal one-dimensional model show finite-coupling
quantum-source corrections beyond a prescribed classical drive, together with spectral reconstruction and occupancy redistribution for squeezed
vacuum and squeezed coherent sources. The squeezing parameter and phase provide additional control knobs, beyond classical amplitude modulation, for both sideband structure and occupied weight. This work provides a theoretical framework for
quantum Floquet engineering of condensed matter with an externally prescribed
quantum light source.
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Mesoscale and Nanoscale Physics
Inferring stealthy hyperuniform correlations from quantum transport
Natanael C. Costa, Mauro S. Ferreira, Caio Lewenkopf et al. (+4 more)
Stealthy hyperuniform disordered systems exhibit strongly suppressed long-wavelength fluctuations, producing correlated disorder with unusual consequences for wave propagation. A central quantity characterizing these systems is the stealthiness parameter $\chi$, which controls the range of excluded
Fourier components in the disorder spectrum. However, in realistic settings, the microscopic disorder configuration may not be directly accessible, making it challenging to determine $\chi$ from structural information alone. Here, we propose a conductance-based inverse protocol to recover stealthy hyperuniform correlations from transport data. As a proof of concept, we study spinless
fermions in a one-dimensional tight-binding chain connected to clean semi-infinite leads, with on-site disorder generated by imposing a stealthy spectrum $S(k)=\Theta(|k|-K)$, where $K=2\pi\chi$. The energy-dependent transmittance is computed using a recursive Green's function method and compared with target spectra through a misfit function defined over an energy window. We show that the position of the sharp drop separating high- and low-transmittance regions is strongly controlled by $\chi$, while the disorder strength $W$ mainly affects the absolute magnitude of the transmittance. As a result, the misfit function displays a clear minimum close to the target stealthy parameter. Our results demonstrate that transmittance spectra can serve as fingerprints of stealthy hyperuniform disorder, providing a practical route to infer correlated-disorder parameters from transport measurements.
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All authors Natanael C. Costa, Mauro S. Ferreira, Caio Lewenkopf, Felipe A. Pinheiro, Paul J. Steinhardt, Salvatore Torquato, Carlo Vanoni
Mesoscale and Nanoscale Physics · Cross-listed from cond-mat.dis-nn
Skin-Anderson Localization Transition in Strongly Coupled Disordered Non-Hermitian Chains
S Rahul
The interplay between disorder and non-Hermitian effects gives rise to a variety of intriguing localization phenomena. While disorder tends to localize the eigenstates through Anderson localization, non-Hermitian non-reciprocity promotes the formation of skin modes by driving the eigenstates toward the system boundaries giving rise to non-Hermitian skin effect (NHSE). In this work, we investigate the interplay between these competing mechanisms in a two-leg ladder consisting of a Hatano-Nelson chain coupled to a Hermitian chain via asymmetric inter-chain hopping, with strong disorder present in both chains. We show that tuning the asymmetry of the inter-chain coupling induces successive transitions in the nature of the eigenstates, from skin localization to Anderson localization and subsequently back to skin localization. Remarkably, the non-Hermitian skin effect re-emerges even though the energy spectrum exhibits a line-gap
topology, demonstrating that robust skin localization can persist beyond the conventional point-gap regime.
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Mesoscale and Nanoscale Physics · Cross-listed from cond-mat.str-el
Sum rules and density-wave modes in spin-singlet fractional quantum Hall fluids
Ritajit Kundu, Rakesh K. Dora, Dung Xuan Nguyen et al. (+1 more)
Fractional
quantum Hall (FQH) states are prototypical examples of strongly interacting topologically ordered systems. In this work, we obtain thermodynamic fits on the plane for the pair correlation function, and its
Fourier transform, the static structure factor, of two-component
spin-singlet Halperin and Jain FQH fluids by expanding them in the recently introduced basis of the orthogonal associated Laguerre
polynomials [Fulsebakke et al., SciPost Phys. 14, 149 (2023), https://doi.org/10.21468/SciPostPhys.14.6.149 ] and ascertaining the expansion coefficients by fitting them to large-system Monte Carlo data evaluated using their trial wavefunctions. In this fitting procedure, aside from constraining the exact short-distance behavior of the wavefunction, we also derive and enforce the sum rules that the long-wavelength expansion of the static structure factor must adhere to. We show that incorporating these constraints is crucial for obtaining numerically stable and accurate values of the long-wavelength Girvin-MacDonald-Platzman (GMP)/symmetric density-wave excitation gap. We further extend this approach to
spin-resolved density-correlation functions, enabling the evaluation of the gap of the antisymmetric density-wave mode for these
spin-singlet FQH states. Finally, we use the density-correlators to compute variational energies of the states and construct phase diagrams for bilayer FQH systems. These could be relevant for understanding recent bilayer FQH experiments that map out the phase diagram by tuning the interlayer separation and density-imbalance/layer-polarization.
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All authors Ritajit Kundu, Rakesh K. Dora, Dung Xuan Nguyen, Ajit C. Balram
Mesoscale and Nanoscale Physics
Assessing fidelity-limiting factors and achieving single-qubit gate fidelity beyond 99.999% in driven silicon spin qubits
Kenta Takeda, Akito Noiri, Takashi Nakajima et al. (+4 more)
In
semiconductor single-
spin qubits, high-fidelity
quantum gates have been demonstrated; however, achieving consistent performance remains challenging due to variations in driven
qubit coherence, which is less explored than free-
evolution coherence such as $T_2^*$. Here, we report single-
qubit gate fidelities above 99.999%, achieved by dramatically extending the driven-
spin coherence time and suppressing off-resonant driving effects that are detrimental to accurate fidelity benchmarking. We demonstrate that removing proximal reservoirs significantly enhances the
spin-locking coherence time ($T_{1\rho}$), a critical metric for
qubits under microwave driving. Furthermore, we reveal that in typical
spin qubit setups using parity readout and rectangular pulses, off-resonant excitation of neighboring
qubits causes substantial benchmarking artifacts. By optimizing device conditions to mitigate microwave-induced degradation and implementing spectrally tailored pulse shaping, we achieve a ${\pi}/2$ gate fidelity of 99.99920(2)%, with remaining errors primarily limited by incoherent noise. These results showcase the mechanisms that bound fidelity benchmarking in state-of-the-art silicon
spin qubits and provide practical guidelines for achieving and verifying high fidelities in these systems.
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All authors Kenta Takeda, Akito Noiri, Takashi Nakajima, Leon C. Camenzind, Takashi Kobayashi, Giordano Scappucci, Seigo Tarucha
Mesoscale and Nanoscale Physics · Cross-listed from cond-mat.str-el
Influence of interactions on the chiral effect in $1D$ Dirac semimetal
Maksim Ulybyshev and M.A.Zubkov
We consider the 1D Su-Schrieffer-Heeger (SSH) model. It was recently shown that, for the noninteracting model in its Dirac semimetal phase, the linear response of the axial charge density to an external electric field is proportional to the electrical conductivity in the presence of finite dissipation, with the proportionality factor determined by the coupling constants. This relation may be viewed as a manifestation of the chiral effect, which is a dimensional reduction of the 3D chiral
magnetic effect. In the present work, we investigate the same model in the presence of two versions of local Hubbard-type interactions using numerical
Quantum Monte Carlo simulations. We find, within the numerical resolution and for the parameters studied, that, even in the regime where sufficiently strong interactions drive the system into a Mott insulating phase, the proportionality between the induced axial charge density and the electrical conductivity remains unchanged. This result indicates that the chiral effect is not renormalized by local Hubbard interactions.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Boosting self hybridized exciton polaritons with metal clad WS2 waveguides
Filip Majstorovic, Masoud Taleb, Victor DeManuel-Gonzalez et al. (+2 more)
The formation of Fabry Perot and guided wave self hybridized
exciton polaritons in two dimensional materials results in long range
exciton energy transfer and strong
exciton exciton interactions. Here, we demonstrate that the coupling strength between photonic modes and
excitons is significantly boosted by
embedding the active excitonic layer in a metal clad WS2 waveguide. The photonic modes in this waveguide exhibit modified dispersion properties for both Fabry Perot type and guided wave
exciton polaritons compared to pure WS2 flakes, and show an increased couplingr strength. Our results provide a robust approach for controlling
exciton photon interactions and their coupling strength in hybrid
heterostructures.
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All authors Filip Majstorovic, Masoud Taleb, Victor DeManuel-Gonzalez, Kai Rossnagel, Nahid Talebi
Mesoscale and Nanoscale Physics
Studying electron beam coherence using plasmon interference
Evelijn Akerboom, F. Javier García de Abajo and Albert Polman
Energetic electrons create distinct cathodoluminescence (CL) angular distributions upon interaction with dielectric and plasmonic nanostructures, providing valuable information on coherences in the excitation pathways. A counterintuitive prediction is that the CL signals arising from the excitation associated with different lateral regions of an extended electron wave are mutually incoherent and do not interfere, while the signals originating from different structures within the electromagnetic field of a narrow electron beam are mutually coherent. We present conclusive experimental evidence of these effects by examining the angular CL emission profile from defocused electron-beam excitation of a thin silicon nitride film, which is shown to follow an incoherent sum of CL excitations within the electron beam spot. In contrast, CL interferences are observed for separated plasmonic scatterers excited within the evanescent field of a single electron. Coherence may be recovered through correlations between emitted light and post-selected electron states, for which we propose a measurement geometry that erases which-path information of the electron trajectory.
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Mesoscale and Nanoscale Physics
Strong coupling between antiferromagnetic magnons and spoof surface plasmons
Yamin Sun, Ka Shen and H. Y. Yuan
Hybrid magnonic system provides a versatile platform for coherent information exchange between
spin excitations and other physical degrees of freedom. While strong coupling between
magnons and spoof plasmons has been observed based on ferrimagnetic spheres and localized microwave resonators, it remains unexplored whether coherent
magnon-plasmon coupling can be achieved in planar
magnetic structures. Here we study the hybridization of antiferromagnetic (AFM)
magnons and spoof surface plasmons in a planar
heterostructure consisting of an AFM thin film, a dielectric spacer, and a structured metal surface. By analytically solving the coupled Maxwell and magnetization dynamics equation, we predict strong
magnon-plasmon coupling in the terahertz regime, manifested by pronounced avoided crossings in the dispersion. The coupling originates from the spatial overlap between magnonic and plasmonic modes in the dielectric spacer, and can be efficiently tuned through
geometric parameters of the system. The calculated cooperativity confirms that the hybrid system can operate in the strong coupling regime, enabling coherent information transfer between
magnons and plasmons. Our results establish a planar platform for plasmon-
magnon hybridization, which is more amenable to on-chip manipulation and integration.
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Mesoscale and Nanoscale Physics
Anisotropic magnon spin transport in CrPS$_4$
Krishnaraajan Sundararajan, Muhammad Zohaib, Yulia Kreminska et al. (+2 more)
Crystal anisotropy provides a powerful route for realizing direction-dependent transport in solid-state systems. While its influence on electronic transport is well established, the role of anisotropy in
magnon spin transport in van der Waals magnets is largely unexplored. Here, in a nonlocal geometry, utilizing the monoclinic van der Waals antiferromagnet CrPS$_4$, we observe pronounced anisotropy in both electrically and in thermally excited
magnon spin transport. Electrically generated
magnons exhibit a
magnon spin conductivity at least 2.2 times larger and a
spin diffusion length at least 2.7 times longer for transport along the crystallographic-b axis compared to the crystallographic-a axis, where $\lambda_m^{a} \sim$ 211 nm and $\lambda_m^{b} \geq$ 575 nm. In comparison, at 8T, we find the nonlocal second-harmonic resistance associated with thermally excited
magnons to be $\sim$7 times larger along the crystallographic-b axis at 25K. We further show that a
magnon spin diffusion length cannot be reliably extracted from the nonlocal second-harmonic resistance, owing to the extended temperature profile within CrPS$_4$. Likewise, we show that the anisotropy in the
spin Seebeck coefficients cannot be reliably estimated from the thermally excited
magnon spin transport alone, as it is intertwined with the anisotropic heat conductivity of CrPS$_4$. Utilizing the electrically generated
magnon spin transport, we demonstrate that intrinsic crystalline anisotropy serves as an effective control parameter for tuning
magnon spin transport, opening new avenues for magnonic device engineering.
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All authors Krishnaraajan Sundararajan, Muhammad Zohaib, Yulia Kreminska, Sytze H. Tirion, Bart J. van Wees
Mesoscale and Nanoscale Physics
Revealing time characteristics of optical excitations in dielectric and plasmonic structures through cathodoluminescence interferometry
Evelijn Akerboom, Hirohsi Sugimoto, Minoru Fujii et al. (+5 more)
Cathodoluminescence (CL) spectroscopy provides access to optical excitations with nanometer spatial resolution, but direct time-resolved measurements of optical resonances remain challenging. Here, we demonstrate that CL interferometry provides access to the temporal response, phase behavior, and modal spectral structure of resonant nanoscale scatterers without requiring ultrafast pump-probe schemes. We develop an analytical framework in which
Fourier transformation angle- and frequency-resolved CL interferograms yields the decay time of optical resonances governed by the linear optical response. Multimode resonators exhibit characteristic temporal CL beating signatures associated with spectral mode splitting. By exploiting transition radiation emitted from a nearby metallic surface as a broadband reference, we further demonstrate phase
retrieval and cross-correlation measurements between instantaneous and resonant emission processes. Experimental measurements on Au nanoparticles, broadband plasmonic emitters, Au nanostars, and Si nanospheres supporting multipolar Mie resonances confirm the theoretical predictions, and decay times in the range 1-10 fs are derived for each system. Our results establish CL interferometry as a powerful approach for accessing spectral, spatial, and phase information within a single nanoscale measurement with fs resolution.
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All authors Evelijn Akerboom, Hirohsi Sugimoto, Minoru Fujii, Nicolas Pazos-Perez, Ramon A. Álvarez Puebla, A. Femius Koenderink, F. Javier García de Abajo, Albert Polman
Mesoscale and Nanoscale Physics
From Zero to Mega-Gauss Fields: Comprehensive Magnetophotonic Spectroscopy of Graphene Dirac Cones
Shojiro Takeyama and Hiroaki Saito
We investigate the infrared magneto-optical response of n-doped epitaxial
graphene on 4H-SiC in ultrahigh
magnetic fields up to 560~T, utilizing single-turn coil and electromagnetic flux compression techniques. The measured absorption spectra are anomalously broad, strongly deviating from conventional cyclotron resonance. Angle-resolved photoemission spectroscopy (ARPES) reveals a distorted Dirac dispersion featuring a “camel-back" structure with an energy gap of $E_g \sim 0.2$~eV. Using the band parameters extracted via a generalized bilayer
graphene model, we construct a Landau level (LL) fan chart that dictates a critical level crossing between the $N=0^+$ and $N=0^-$ states near 160–200~T. At this threshold, the optical transition mechanism undergoes a dramatic shift from an electron-dominated collective mode to a cooperative electron-hole collective excitation. Furthermore, the extreme-field absorption spectra under thulium fiber
laser excitation ($\hbar\omega_0 = 0.636$~eV)—culminating in a massive resonance near 400~T with a shoulder at 200~T—are excellently reproduced by a collective Alfvén wave model. This analysis also evidences a
magnetic-field-induced enhancement of the sublattice potential asymmetry parameter (from 0.10~eV to 0.12~eV). This directly signifies that the macroscopic electron-hole band asymmetry is further amplified by the applied
magnetic field. Ultimately, the field-induced energy inversion generates a strongly interacting, fully compensated electron-hole
plasma. The resonant excitation of Alfvén waves in this regime demonstrates that a pristine tabletop analog to the relativistic electron-positron
plasmas found in astrophysical extremes can be elegantly realized within a 2D
graphene system.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Nanoscale graphitization and defect evolution in silicon-vacancy center-containing nanodiamonds under high-pressure high-temperature annealing
M. De Feudis, B. Yavkin, L. Henry et al. (+6 more)
Group-IV color centers, such as the silicon-vacancy (SiV) defect, are highly promising for solid-state
quantum technologies. However, nanodiamonds typically exhibit significant
lattice strain and structural disorder, which degrade their optical properties and hinder the resolution of the fine spectral structure at cryogenic temperatures. High-pressure high-temperature (HPHT) annealing offers a potential route to relax internal strain, although the phase stability of diamond at the nanoscale under such conditions remains poorly constrained. Here, we investigate the structural
evolution of nanodiamonds during HPHT annealing using a Paris-Edinburgh press coupled with in situ synchrotron X-ray diffraction at SOLEIL. A dedicated sample assembly combining nanodiamonds - NaCl - Pt enabled accurate pressure-temperature calibration and real-time monitoring of phase transformations. The diffraction data reveal that the onset of diamond-to-graphite transition occurs at approximately 1800 K at 2 GPa and 2120 K at 4 GPa under the applied HPHT heating protocol. These experimentally determined graphitization onsets define a practical pressure-temperature processing window for HPHT annealing of nanodiamonds while avoiding detectable graphitization and provide a calibrated framework for reliable off-beam annealing treatments that avoid graphitization. Photoluminescence measurements on samples annealed below the graphitization threshold show improved optical response, with partial resolution of the SiV fine structure at 12 K. These optical measurements suggest a relationship between nanoscale phase stability and the optical response of individual SiV-containing nanodiamonds following HPHT annealing. The experimentally established HPHT processing window provides a practical framework for the controlled processing of
quantum nanodiamonds while avoiding graphitization.
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All authors M. De Feudis, B. Yavkin, L. Henry, K.O. Ho, M.-P. Adam, P. Goldner, F. Benedic, S. Desgreniers, J.-F. Roch
Mesoscale and Nanoscale Physics
Bitap Raj Thakuria and Himangshu Prabal Goswami
Slow cyclic modulation of an open
quantum system can generate a
geometric contribution to its energy transfer statistics, separable from the dynamic background. In this work we construct an experimentally anchored four state open system model for a gate-tunable WSe2/WS2 moiré
exciton manifold within a population level full counting statistics framework. We first drive the system uniformly through a closed gate and pump loop and separate the
geometric contribution from the dynamic background by reversing the loop direction. We then examine how this response changes with environmental rates,
exciton coupling, control conditions, and static spectral broadening. A shorter cycle period followed by nonuniform traversal of the driving loop substantially improves detectability while preserving the
geometric response. Combined with enhanced
phonon relaxation and reduced radiative loss, this gives about a fourteenfold fixed time signal to noise gain relative to the uniform loop. Our results show that the
geometric phonon response remains robust against realistic variations in the system and its environment, and that we can improve its detectability more effectively by suppressing dynamical noise through frequency modulated driving.
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Mesoscale and Nanoscale Physics
Topological states of generalized dissipative Majorana wires
Farokhnaz Hosseinifar and Ali G. Moghaddam
We study the generalized one-dimensional (1D)
quantum dissipative models corresponding to a Majorana wire which can possess more than one Majorana bound state at each end. The system consists of a 1D fermionic open
quantum system whose dynamics is governed by a quadratic Lindblad equation. Using the adjoint Lindblad equation for the fermionic two-point correlations, we find the gaps in the damping and purity spectra of a generic 1D model. Then, using the
symmetry-based classification, we show that a winding number as the topological invariant can be defined which distinguishes different steady states of the system in the presence of damping and purity gaps. Then we focus on certain models with different Lindblad
quantum jump terms and explore their phase diagrams by calculating the damping and the purity gaps as well as the winding number. In particular, we show that by inclusion of
quantum jumps between next-nearest-neighbor sites, higher winding numbers and, equivalently, more Majorana bound states can be achieved. Also, by introducing imbalanced couplings, we can switch between states with negative and positive winding numbers. Finally, we should mention that since our formulation is based on the fermionic correlations rather than the Majorana operators, it can be easily extended to the dissipative topological phases belonging to other
symmetry classes.
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Mesoscale and Nanoscale Physics
Higher-Order Topological States with Cleavage-Dependent Dirac Mass
Hongyu Chen, Min Long, Chuang Chen et al. (+1 more)
Topological
quantum chemistry based on local charge profiles lacks predictive power for the crystalline cleavage of higher-order topological
insulators (HOTIs). By cleaving an obstructed atomic
insulator, we discover a topological phase characterized by e/2-fractional charges localized at precisely half of the corners, while the remaining empty corners host complementary vacancies of interstice charge. These zero-energy charge vacancies and topological corners form a spatially balanced geometry, separately localized at four corners. Crucially, we demonstrate that the emergence of corner zero modes dictates that specific dangling bonds acting as the mass of a Dirac
fermion-must explicitly expose in, and subtly slope toward, the corner regions. This strict directionality is verified by the anisotropic
evolution of the mass term within a (2+1) dimensional parameter space. Moreover, we find that the topological corners acquire lower
entanglement entropy compared to the bulk, a behavior opposite to that of the real-space energy distribution which forms an energy-
entropy compensation, essentially derived from the topological charge compensation. Our work paves the way for the local chemical environment at topological boundaries, and demonstrates the higher order
quantum transport counterparts for high energy Dirac physics.
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All authors Hongyu Chen, Min Long, Chuang Chen, Zi Yang Meng
Mesoscale and Nanoscale Physics
Dynamics of amorphous membranes in the two-dimensional limit
Liga Jasulaneca, Alberto Martín-Pérez, Hongji Zhang et al. (+7 more)
Atomically thin mechanical resonators have been realized predominantly in crystalline two-dimensional (2D) materials, such as
graphene, where long-range crystalline order sets their elastic properties and defines their nonlinear resonant behavior. Extending these concepts to the amorphous 2D limit has remained largely unexplored. Here, we demonstrate that monolayer amorphous carbon (MAC) forms suspended membranes that support optothermal actuation and sensitive interferometric readout across both linear and nonlinear regimes of its resonant motion. We resolve thermomechanical motion, driven resonances, and multimode spectra in MAC nanodrums. The frequencies of fundamental vibration modes correspond to unusually low pretensions, placing monolayer MAC nanodrums in a regime where
geometric nonlinearities, stress heterogeneity, and mode coupling emerge at comparatively low drive powers. Consistently, we observe pronounced nonlinear dynamics, including hardening, softening, and mixed Duffing responses, nonlinear damping, parametrically excited modes, and signatures of intermodal coupling. These results establish MAC as a robust nanoelectromechanical platform and open an experimental route to disorder-governed nanomechanics in the 2D amorphous limit.
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All authors Liga Jasulaneca, Alberto Martín-Pérez, Hongji Zhang, Prertahn Munireternam, Natalia A. Mamchik, Chee-Tat Toh, Artem K. Grebenko, Barbaros Özyilmaz, Makars Šiškins, Farbod Alijani
Mesoscale and Nanoscale Physics
Moving Analogue Horizons in Stationary Ferroelectrics
David Galvez-Poblete, Rubén M. Otxoa, Alvaro S. Nunez et al. (+1 more)
We show that a traveling modulation of the polarization-gradient stiffness in a ferroelectric material induces an effective flow in its collective polarization dynamics. Within a controlled local approximation, small polarization fluctuations, or ferrons, obey a massive Klein-Gordon equation with flow. Unlike conventional analogue-
gravity platforms, the effective flow originates from the modulation of the material parameters rather than from the physical transport of the medium. This mechanism enables mobile analogue horizons separating sub-ferronic and super-ferronic regions, the latter supporting negative-norm antiferron modes. Their coupling to positive-norm ferrons gives rise to superradiant-like amplification, while the effective mass gap can be tuned independently through an external electric field. Ferroelectric systems therefore provide a novel and experimentally controllable platform for analogue
gravity with massive scalar excitations.
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All authors David Galvez-Poblete, Rubén M. Otxoa, Alvaro S. Nunez, Sebastian Allende