Other Condensed Matter · Cross-listed from physics.optics
GHz control of THz QCL band structure and gain by standing acoustic strain
Alexander S. Kuznetsov, Valentino Pistore, Lutz Schrottke et al. (+2 more)
Active frequency comb generation and waveform control are central challenges in the terahertz (THz) domain. In THz
quantum cascade
lasers (QCLs), these functions have typically been achieved through active bias modulation, which alters the operating point of the device and imposes severe limitations on its flexibility. To address these challenges, we propose an approach based on the direct modulation of the QCL bandstructure using GHz-frequency standing bulk acoustic waves (BAWs), promising direct and localized control of the optical gain and chromatic dispersion. To this end, we fabricated a bulk acoustic transducer on top of a THz QCL in order to excite GHz standing BAWs within its active region. We demonstrate that
radio-frequency driving of the transducer leads to the tunable generation of standing BAWs in 5-12 GHz frequency range with wavelengths commensurate to the QCL period length. The effect of the BAW on the QCL bandstructure is revealed by measuring photoluminescence (PL) of the active region, where the BAW strain leads to a considerable modulation of the PL energy up to a few meV around its non-modulated value. We also develop a model and perform bandstructure simulations to predict the effect of the BAW on the QCL subband structure and gain. These results mark the first demonstration of dynamic bandstructure modulation in a THz QCL using GHz acoustic strain, introducing a fundamentally new paradigm that establishes a powerful synergy between QCLs and BAWs towards coherent control and frequency comb engineering in the THz domain.
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All authors Alexander S. Kuznetsov, Valentino Pistore, Lutz Schrottke, Klaus Biermann, Xiang Lü
Strongly Correlated Electrons
Chemical and optical control of chiral-domain dynamics in 1T-TaS$_2$
Qingzheng Qiu, Mengxian Zhao, Roman Mankowsky et al. (+14 more)
Optical control of
symmetry-breaking
quantum phases is often constrained when one domain is strongly favored in
equilibrium. This limitation is exemplified by the
chiral charge-density-wave (CDW) order in 1T-TaS$_2$, where pristine samples predominantly select a single chirality. Here we show that free-energy landscape engineering through Ti substitution enables a distinct nonthermal pathway for ultrafast
chiral-domain redistribution. Ti doping stabilizes coexisting
chiral domains and tunes their relative stability, allowing femtosecond excitation to drive an asymmetric and anisotropic redistribution from the dominant toward the minority chirality. The subpicosecond response follows a $\sim2$ THz amplitude mode and is consistent with a
phonon-assisted pathway involving transient domain-wall configurations. Our results establish free-energy landscape engineering as a strategy for selecting nonequilibrium transition pathways.
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All authors Qingzheng Qiu, Mengxian Zhao, Roman Mankowsky, Henrik Till Lemke, Serhane Zerdane, Mathias Sander, Zihao Tao, Qizhi Li, Xiquan Zheng, Shilong Zhang, Qian Xiao, Xinyi Jiang, Xin Liu, Shih-Wen Huang, Yang Yang, Sheng Meng, Yingying Peng
Strongly Correlated Electrons
Non-Hermitian skin effect in periodic, random, and quasiperiodic systems
F. Iwase
The non-Hermitian skin effect (NHSE), which drives bulk states toward system boundaries, modifies bulk-boundary correspondence and complicates the identification of topological edge modes. Although breaking translational
symmetry is known to influence this behavior, a systematic comparison of different structural classes remains limited. Here we investigate periodic, random, and quasiperiodic (Fibonacci) systems using a one-dimensional non-Hermitian
quantum walk model. By matching the local scattering parameters in a topologically nontrivial regime, we isolate the role of spatial structure in the presence of the NHSE. We find that periodic systems exhibit pronounced boundary accumulation of bulk states. Random systems suppress this accumulation through Anderson localization, but the topological gap becomes partially filled with localized in-gap states. In contrast, the Fibonacci quasiperiodic system suppresses large-scale boundary accumulation while maintaining a well-defined topological gap. Analysis of the wave functions suggests that the hierarchical quasiperiodic structure fragments bulk states across multiple length scales, thereby mitigating the NHSE. These results identify deterministic quasiperiodicity as a distinct structural regime for controlling non-Hermitian skin dynamics and isolating topological boundary modes.
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Mesoscale and Nanoscale Physics
Solitary waves in a phononic integrated circuit
Timothy M.F. Hirsch, Xiaoya Jin, Nicolas P. Mauranyapin et al. (+6 more)
Solitons are universal nonlinear excitations that appear in settings as varied as optics, water waves, and
quantum gases [1-5]. While reduced models of
soliton dynamics are well established, their validity and dynamical behaviour in strongly nonlinear regimes with frequent interactions remain largely unexplored experimentally. Progress has been constrained by the difficulty of simultaneously achieving precise control of dispersion and nonlinearity, together with the temporal and spatial resolution required for dynamical observations. Here we overcome these difficulties by producing acoustic
solitons in integrated phononic waveguides. We exploit the interplay between waveguide dispersion and mechanical Kerr nonlinearity to generate 'dark'
solitons that persist over metre-scale propagation distances. The slow
phonon velocity allows direct imaging of hundreds of dark
soliton collisions – two orders of magnitude more than have previously been accessible [6, 7] – as well as
soliton fission and the melting of a
soliton Wigner
crystal. Furthermore, the unprecedented dynamical resolution allows us to verify two long-predicted aspects of dark
soliton behaviour: the existence of a collisional phase shift and two depth-dependent collision regimes [8, 9]. These results not only illuminate fundamental nonlinear energy transport processes, but also show a path towards acoustic versions of
soliton-enabled technologies such as frequency combs and mode-locked
lasers [1, 2, 10].
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All authors Timothy M.F. Hirsch, Xiaoya Jin, Nicolas P. Mauranyapin, Nishta Arora, Erick Romero, Matthew Reeves, Glen I. Harris, Warwick P. Bowen, Christopher G. Baker
Mesoscale and Nanoscale Physics
Electron scattering by a magnetic monopole in solid-state experiments
P. S. Sidorov, N. A. Vlasov, I. S. Terekhov et al. (+1 more)
The scheme of experiment for studying electron scattering in the field of a
magnetic monopole in two dimensional electron gas is proposed. The differential scattering cross section is obtained in the eikonal approximation. For unpolarized initial electron, the differential cross section coincides with that in the field of an infinitely long solenoid, up to redefinition of a
magnetic flux. It is shown that the scattered electron becomes polarized even for unpolarized initial electron. Besides, in an experimental setup similar to the
Hall experiment, the
spin polarization arises in the direction perpendicular to the electron current.
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All authors P. S. Sidorov, N. A. Vlasov, I. S. Terekhov, A. I. Milstein
Materials Science
Mechanical Origin of High-Temperature Thermal Stability in Platinum Oxides
Fangyuan Ma, Mengzhao Sun, Xuejian Gong et al. (+3 more)
Platinum
oxides are vital catalysts, but their limited thermal stability hinders applications. Recent studies have uncovered a structural transition in two-dimensional platinum
oxides that significantly enhances their thermal resilience by several hundred Kelvin. Herein, we demonstrate that this enhanced stability stems from the mechanical robustness of the elastic network at the atomic scale. Prior to the transition, an over-constrained
lattice generates localized states of self-stress through an incommensurate Moiré pattern with the platinum substrate, reducing thermal endurance. After the transition, the
oxide shifts to a mechanically flexible structure with balanced degrees of freedom and constraints. The isostatic network, together with the platinum substrate, forms a commensurate Moiré superlattice that relaxes elastic energy and enhances stability. These findings highlight the fundamental role of network connectivity in governing thermal stability, and provide a design principle for catalysts in extreme environments.
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All authors Fangyuan Ma, Mengzhao Sun, Xuejian Gong, Jun Cai, Zhujun Wang, Di Zhou
Materials Science
Ultrafast optical route to coupled ferroelectric and altermagnetic switching
Yuhao Gu, Yu-Hui Song, Peng-Jie Guo et al. (+5 more)
Exploring novel magnetoelectric coupling mechanisms to achieve control of ferroelectric polarization and magnetism is highly significant for both fundamental science and electronic device applications. Although extensive studies have been conducted on electrical switching of magnetism in multiferroic materials, simultaneous ultrafast
laser switching of ferroelectric polarization and altermagnetism remains unexplored. In this letter, we propose that the ultrafast
laser can be used to switch ferroelectric polarization and altermagnetism concurrently in charge-order-induced altermagnetic ferroelectrics. Building on this idea, we further demonstrate that such dual switching can be realized in charge-order-induced altermagnetic ferroelectric LiV$_2$F$_6$ by
symmetry analysis and time-dependent density functional theory (TDDFT) calculation. Given that LiV$_2$F$_6$ has already been experimentally synthesized, our work not only provides an ideal material platform for experimentally realizing simultaneous switching of ferroelectric polarization and altermagnetism but also holds potential application value in future ultrafast spintronic devices.
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All authors Yuhao Gu, Yu-Hui Song, Peng-Jie Guo, Yihao Wang, Zhe Li, Ze-Feng Gao, Huan-Cheng Yang, Zhong-Yi Lu
Materials Science
Profound impacts of interlayer interactions in bilayer altermagnetic V2S2O
Siqi Xu, Qilong Cui, Shaowen Xu et al. (+6 more)
Two-dimensional altermagnets exhibit exceptional potential for low-power spintronics via nonrelativistic
spin splitting and zero net magnetization. Here, we systematically investigate the influence of interlayer interactions on the electronic,
magnetic and
quantum transport properties of
bilayer vanadium oxysulfide (V2S2O), a prototypical layered altermagnet, using DFT and NEGF calculations. Our results reveal that interlayer interactions predominantly modulate the p-orbital derived top valence bands, inducing a profound competitive valence band maximum position between Gamma-point pz and X/Y-point pxy orbitals, with an energy difference as small as 9 meV. Furthermore, interlayer interactions suppress the piezomagnetic effect and impose additional requirements on the type of strain for the
bilayer system, compared to its monolayer counterpart. Out-of-plane external electric fields effectively weaken interlayer coupling by enlarging the energy difference of Gamma/X-Y top valence bands to 170 meV.
Quantum transport simulations on a
bilayer Au/V2S2O/Au two-probe device demonstrate the presence of pronounced
spin current. Interlayer interactions reduce the transmission
spin polarization from nearly 100% (monolayer) to 60% (
bilayer) for energies above the
Fermi level. Notably, gate-voltage modulation exhibits significant asymmetry in controlling charge-to-
spin current conversion efficiency, originating from the out-of-plane
symmetry breaking induced by the electrode geometry. Specifically, a positive gate voltage markedly enhances the contribution of the bottom layer to the overall
spin polarization, while a negative gate voltage induces a marginal reduction of transmission
spin polarization, attributed to the inherently weak polarization contribution of the bottom layer. These findings provide essential insights for the design and optimization of multilayer altermagnetic spintronics.
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All authors Siqi Xu, Qilong Cui, Shaowen Xu, Xianbo Chenwei, Jiahao Zhang, Ruixue Li, Yuan Li, Gaofeng Xu, Fanhao Jia
Materials Science
Experimental investigation of magnetic properties of MnFeCo$_{4}$Si$_{2}$ discovered by GNoME
Shuhei Naganuma and Jiro Kitagawa
AI-driven inorganic materials research has garnered significant
attention due to its ability to reduce the time, labor, and cost associated with experiments. An AI model known as GNoME, recently developed by Google DeepMind, is particularly fascinating because it is integrated with the Materials Project open database. The experimental verification of compounds identified by GNoME is a crucial process for advancing AI-driven materials research. Here, we focus on the
magnetic compound MnFeCo$_{4}$Si$_{2}$ (Materials ID: mp-3203253), which possesses a layered-like structure. Consistent with the GNoME prediction, MnFeCo$_{4}$Si$_{2}$ crystallizes in a rhombohedral structure with a single-phase nature. We have characterized its
magnetic properties and determined that MnFeCo$_{4}$Si$_{2}$ is a soft ferromagnet with a Curie temperature of 1039 K.
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Quantum Gases · Cross-listed from quant-ph
Boundary-sensitive non-Hermiticity of Floquet Hamiltonian: spectral transition and scale-free localization
Bo Li, He-Ran Wang and Fei Song
We report a novel mechanism of boundary-sensitive PT
symmetry breaking in one-dimensional Floquet systems. By designing a time-periodic driving protocol, we realize a Floquet
Hamiltonian that is Hermitian under periodic boundary conditions yet acquires non-Hermitian boundary terms under open boundary conditions due to the non-commutativity of driving
Hamiltonians. We establish that a PT
symmetry breaking transition occurs when the quasienergy bandwidth expands to cover the entire frequency Brillouin zone. This condition highlights a crucial difference from static non-Hermitian systems, where such transitions typically require band touching. Furthermore, we demonstrate that in the PT-broken phase, the eigenstates exhibit scale-free localization, a phenomenon arising from the specific system-size scaling of non-Hermitian terms. Finally, we provide a general framework for constructing multi-band models that exhibit this boundary-induced phase transition.
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Materials Science
Hydrogenation-induced gigantic resistance decrease of palladium films deposited by high pressure magnetron sputtering
Yusuke Ikeda, Takuya Kawada and Yuki Shiomi
We demonstrate a pronounced decrease in the electrical resistance of highly disordered palladium (Pd) films deposited under a high working Ar pressure using a compact film coating system. The resulting resistance change ratio of up to $1/335$ is predominant among those reported previously. Film characterization suggests two primary mechanisms responsible for this significant resistance reduction: atomic force microscopy observation indicates improved electrical contacts among Pd grains, and X-ray diffraction measurement demonstrates hydrogenation-induced crystallization of Pd. These findings offer a simple scheme to enhance hydrogen sensor performance and can contribute to a more comprehensive understanding of the hydrogenation process in Pd.
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Strongly Correlated Electrons
Symmetric Mass Generation Transition and its Nonequilibrium Critical Dynamics in a Bilayer Honeycomb Lattice Model
Zhi-Xuan Li, Yin-Kai Yu, Zi-Xiang Li et al. (+1 more)
Symmetric mass generation (SMG) transitions defy the conventional Landau-Ginzburg-Wilson paradigm by opening a many-body gap without spontaneous
symmetry breaking or topological order, attracting intense interest across particle physics and condensed matter physics. Here, we utilize unbiased
quantum Monte Carlo simulations to investigate the
equilibrium and nonequilibrium critical dynamics of the SMG transition in a
bilayer honeycomb
lattice model. We unambiguously confirm the existence of an SMG transition at $J_{\text{c}}=2.584(8)$ that separates the Dirac semimetal phase from a
symmetry-preserving SMG phase. High-precision extraction of the critical exponents reveals a novel universality class that profoundly departs from mean-field theory. We then extend our study to the nonequilibrium regime, exploring the driven dynamics of the SMG transition. Notably, despite the breakdown of the prerequisites for the celebrated Kibble-Zurek mechanism, the nonequilibrium SMG transition still follows the generalized finite-time scaling. By bridging
equilibrium criticality and nonequilibrium dynamics, our work uncovers the universal critical properties of SMG transitions, providing a solid theoretical basis for future experimental studies of SMG physics.
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All authors Zhi-Xuan Li, Yin-Kai Yu, Zi-Xiang Li, Shuai Yin
Materials Science · Cross-listed from physics.app-ph
Simultaneous measurement of pressure-dependent bulk and interfacial thermal properties in thermal interface materials using square-pulsed source thermoreflectance
Tao Chen, Bingjia Xiao, Xin Qian et al. (+1 more)
Thermal interface materials (TIMs) critically regulate heat dissipation from electronic chips to heat spreaders, yet their thermal conductivity (k), volumetric heat capacity (C), and interfacial thermal resistance (ITR) evolve with mechanical pressure and cannot be determined simultaneously using existing steady-state or transient techniques. As a result, the coupled roles of bulk compaction and interfacial contact in governing heat transport in TIM assemblies remain poorly resolved. Here, we present a square-pulsed source (SPS) thermoreflectance method that enables simultaneous determination of k, C, and ITR in TIM stacks under controlled mechanical loading. By spanning square-wave modulation frequencies from 1 Hz to 10 MHz, SPS probes a broad range of thermal penetration depths, enabling distinction between heat
diffusion in the TIM bulk and interfacial heat transfer at the Al/TIM contact. Measurements on a thermally conductive gel, a thermal pad, and a high-
vacuum grease during compression-unloading cycles reveal distinct pressure-dependent thermal transport mechanisms. The gel and pad exhibit increases in k and C, reduced ITR, and pronounced hysteresis, indicating coupled bulk densification and persistent interfacial conformity during loading cycles. In contrast, the grease shows nearly pressure-independent bulk properties but a strong pressure dependence of ITR, consistent with an interface-dominated response. These results resolve the long-standing challenge of simultaneously quantifying bulk and interfacial thermal transport in mechanically loaded TIM assemblies, enabling experimentally constrained thermal management and reliability analysis in electronic packaging.
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All authors Tao Chen, Bingjia Xiao, Xin Qian, Puqing Jiang
Materials Science
First-Principles Analysis of Chirality-Induced Spin Selectivity at Molecule-Metal Interfaces in Photoemission
Amos Afugu, Gyanu P. Kafle and Zhen-Fei Liu
Spin-resolved photoelectron spectroscopy (PES) probes chirality-induced
spin selectivity (CISS), yet it remains unclear whether the measured
spin polarization reflects molecular chirality itself or the broader electronic structure of the hybrid interface. We present a first-principles analysis of PES
spin polarization at
chiral molecule-metal interfaces, treating the interface holistically rather than as a metal substrate plus a separate molecular
spin filter/polarizer. Using density functional theory within a three-step photoemission framework, we compute the
spin polarization generated in the optical-excitation step for ($M$)- and ($P$)-heptahelicene adsorbed on Au(111) and Cu(111), and for coronene/Au(111) as a non-
chiral control. We find that adsorption strongly reshapes the PES
spin polarization relative to the clean metal surface, but opposite enantiomers yield
symmetry-related responses. These results indicate that changes in the PES
spin polarization are more naturally attributed to the electronic structure of the hybrid interface than to molecular chirality alone.
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Materials Science
Weak Coupling of Diffusional and Phonon-like Modes in Liquids Revealed by Dynamic Kapitza Length
Tao Chen and Puqing Jiang
Understanding heat transfer across solid-
liquid interfaces is central to thermal management and energy technologies, yet whether the interfacial thermal conductance (ITC) depends on the timescale of heating remains unclear. Here we use square-pulsed source thermoreflectance, which combines time-resolved detection with broadband modulation, to probe Al-water and Al-octane interfaces. We observe a reproducible increase of the apparent ITC with modulation frequency. A control Al-silica interface shows no measurable frequency dependence, indicating that the effect is specific to
liquids rather than a generic feature shared by all amorphous materials. We explain the data with a two-channel
liquid picture in which diffusional and
phonon-like modes exchange energy weakly over a finite nonequilibrium length. From the relative magnitude of the thermal penetration depth and the nonequilibrium length, we identify three transport regimes. These findings challenge the common assumption of fully equilibrated
liquid modes and provide experimental constraints for modeling dynamic energy exchange at
liquid interfaces.
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Mesoscale and Nanoscale Physics
Two-dimensional bound excitons in real space and Landau quantization space: A comparative study
Kunxiang Li and Yi-Xiang Wang
The Landau quantization space is based on the respective motion of the electron and hole in a
magnetic field and can provide a new route to understand the bound
exciton behaviors observed in the experiments. In this paper, we study the two-dimensional
exciton properties of monolayer WSe$_2$ in both real space and Landau quantization space. Focusing on the
excitons of zero center-of-mass momentum, we calculate its energy spectrum in both spaces, with the results agreeing well with each other. We then obtain the diamagnetic coefficients and root-mean-square radius, which are consistent with the available $s$ state data in the experiment. More importantly, in the
exciton state $nl$, we find that the dominant electron-hole pair component may shift with the
magnetic field and the Coulomb interactions, and reveal that the
magnetic field will drive the dominant component to be the free electron-hole pair $\{n_e=n+l-1,n_h=n-1\}$, whereas the Coulomb interactions drives it to be the pair of the lower index.
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Materials Science
Distinct memory properties in spin-wave reservoir computing based on synthetic antiferromagnet
Takumu Shinkai, Satoshi Iihama, Kensuke Hayashi et al. (+3 more)
Spin-wave-based physical reservoir computing (RC) is a promising candidate for energy-efficient physical implementations of artificial intelligence because of its potential for nanoscale integration with low power consumption. Most of the previous studies on
spin-wave RC have utilized
spin waves excited in a single-layer ferromagnet. In this study, we focused on
spin waves in a synthetic antiferromagnet (SAF), consisting of two
ferromagnetic layers coupled antiferromagnetically, and investigated additional
memory properties of
spin-wave RC. We theoretically and numerically demonstrate the emergence of two distinct
memory properties in the SAF device due to the distinct
spin-wave characteristics of the acoustic and optical modes inherent in SAFs.
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All authors Takumu Shinkai, Satoshi Iihama, Kensuke Hayashi, Takahiro Moriyama, Shigemi Mizukami, Natsuhiko Yoshinaga
Strongly Correlated Electrons
Dimensionality-Dependent Exciton Dispersion in a Single-Band Mott Insulator
Zhibin Su, Junjian Mi, Shaohua Yan et al. (+9 more)
Excitonic band structure is critical for investigating
exciton dynamics. Theoretically,
quantum effects from exchange scattering between electron-hole pairs significantly modulate
exciton dispersion. Here, we report the direct observation of dimensionality-dependent
exciton dispersion in a single-band Mott
insulator Nb3Cl8 through high-resolution electron energy loss spectroscopy. In the high-temperature phase, the
exciton in Nb3Cl8 hosts an exceptionally large binding energy, and exhibits clear quasi-two-dimensional massless linear dispersion. In contrast, in the low-temperature phase, the
exciton splits into two bands, both displaying three-dimensional
parabolic dispersion. These dramatic changes in the
exciton dispersion stem from the dimensional mutation driven by a substantial enhancement of interlayer coupling across the phase transition. This Letter provides a clear and typical example of how
exciton behavior evolves with dimensionality.
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All authors Zhibin Su, Junjian Mi, Shaohua Yan, Jiade Li, Siwei Xue, Zhiyu Tao, Enling Wang, Xiongfei Shi, Hechang Lei, Zhuan Xu, Jiandong Guo, Xuetao Zhu
Soft Condensed Matter
Finite compressibility and strain hardening in elasto-plastic models of amorphous matter
A. Elgailani, D. Vandembroucq and C. E. Maloney
We study a mesoscopic elasto-plastic model of amorphous matter with varying dimensionless compression modulus, $K/\mu$, where $K$ and $\mu$ are the compression and shear
moduli. We study both cyclic shear with amplitude $\Gamma$ and forward steady shear. In cyclic shear, the terminal behavior is, in order of increasing $\Gamma$: i) trivially elastic, ii) hysteretic but with microscopically reversible limit cycles, iii) diffusive with no return to previously visited configurations. We show that the transition between i) and ii) at the onset point $\Gamma_0$ is determined by the Eshelby back stress, $\sigma_0$, which depends on the Poisson ratio. Systems with smaller $K/\mu$ (more compressible) are effectively harder with a higher $\Gamma_0$ and a correspondingly larger purely elastic regime in cyclic loading. In forward shear, $\sigma_0$ plays a similar role where lower $K/\mu$ results in a higher steady state flow stress, $\sigma_y$. We show that increasing $K/\mu$ increases the amplitude of stress redistribution after a local yielding event without changing the net stress relaxation and relate this to the assumptions in mean-field descriptions of amorphous solids. A striking feature of the model is the emergence of a complex hardening behavior in the absence of any ad-hoc hardening parameters: a transition between a kinematic and an isotropic hardening behavior precisely at $\Gamma_0$ associated with the hysteresis transition. The enhanced plastic response for incompressible systems is also seen in amorphous
alloys where it is usually attributed to excess free volume, while in the present model, it arises from the dependence of the Eshelby backstress on the Poisson ratio. Our results should have important implications for amorphous metallic
alloys or other glassy systems where $K/\mu$ can vary with composition, age, quench procedure, or mechanical processing history.
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Disordered Systems and Neural Networks
Non-Hermitian Mosaic Maryland model
Zhenning Wang, Ni Lu, Dan Liu et al. (+2 more)
We introduce the non-Hermitian mosaic Maryland model, where a discrete modulation period and a non-Hermitian phase are incorporated into the potential, rendering the originally exactly solvable system generally non-integrable. This model provides a unique platform to investigate how structural modulation governs localization in complex quasiperiodic potentials. Using Avila's global theory, we analytically derive the exact Lyapunov exponent and obtain explicit formulas for the complex mobility edges. Remarkably, for modulation periods kappa >= 2, the system intrinsically hosts kappa-1 robust extended bands that persist independently of the potential strength and non-Hermiticity. We further characterize the topological nature of these phases via the spectral winding number. Unlike the standard Maryland model, the mosaic modulation induces mobility edges, and the resulting phase transitions are continuous, reflecting the non-integrable nature of the system. Numerical calculations of the inverse participation ratio and fractal dimension confirm the analytical predictions for the asymptotic form of the mobility edges in the large non-Hermiticity limit. This work establishes structural design as a powerful degree of freedom for engineering wave transport and enhancing the robustness of extended states in non-Hermitian systems.
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All authors Zhenning Wang, Ni Lu, Dan Liu, Xiaosen Yang, Xianqi Tong
Superconductivity
A mechanism for nonmonotonic $T_{c,max}(n)$ in multilayer cuprates
Pavel Kornilovitch
We propose an explanation of the observed dependence of the maximal critical temperature $T_{c,max}$ on the number of conducting layers $n$ in layered copper-
oxide superconductors within the preformed pair mechanism. Copper-oxygen planes fine-tune the
lattice anisotropy and regulate the balance between the attractive and kinetic energies of carrier holes. To maximize the Bose-Einstein condensation temperature, real-space pairs must be compact and light at the same time. Generally, $T_{c,max}$ increases between $n = 1$ and $n = 3$ because pairs become lighter. For $n > 3$, the rising kinetic energy weakens the pairs, leading to inflated pair volumes and reduced $T_{c,max}$. By varying model parameters, the peak of $T_{c,max}(n)$ can be tuned to $n = 2$, $n = 3$, or $n > 3$. We also discuss strategies for using this knowledge to boost $T_{c,max}$ beyond the current record of 138 K.
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