arXiv subjects

Haiyu Meng

Publications and source records attributed to Haiyu Meng.

11 recordsLinked to original sources

arXiv2026

High-Throughput Computational Discovery of Inverted Resistive Switching in Two-Dimensional Materials

Atomristors, non-volatile resistive switching devices based on two-dimensional (2D) monolayers, are promising building blocks for energy-efficient memory and neuromorphic computing. However, their design remains restricted to a few materials such as MoS2 and h-BN, limiting functional diversity and design flexibility. Here, a high-throughput computational framework combining density functional theory, machine-learning molecular dynamics, and quantum transport simulations screens about 2,900 exfoliable monolayers for vacancy-mediated resistive switching, identifying 17 thermally stable candidates in two mechanistically distinct classes. In Class 1 monolayers, such as GaS, Au adsorption at the native vacancy introduces conducting states, switching the insulating monolayer from a high- to a low-resistance state (HRS-to-LRS). Class 2 monolayers, comprising ionically bonded metal oxyhalides and nitrohalides such as BiOCl, exhibit previously unreported inverted switching. Vacancy-released electrons delocalize and push the Fermi level into the conduction band, placing the device natively in the LRS; Au adsorption re-localizes these carriers and returns the Fermi level to the gap, driving LRS-to-HRS switching. Quantum transport simulations confirm both mechanisms, while migration-barrier calculations identify the electrode-2D separation as a key parameter governing Au migration and the resistance window. These findings expand the atomristor landscape and establish complementary switching as a design paradigm for multifunctional memory and neuromorphic hardware.

cond-mat.mtrl-sci↗

arXiv2026

Mirror-Symmetry-Enforced Photonic Altermagnet

Altermagnets host momentum-dependent spin splitting without net magnetization, a symmetry-enforced band phenomenon whose photonic analogues have so far been realized only in square lattices governed by fourfold rotation. Here we introduce a photonic altermagnet on a hexagonal lattice whose helicity splitting is governed by mirror rather than rotational symmetry. Elliptical chiral elements of alternating handedness, placed at the vertices of a regular hexagon, leave the two opposite-chirality sublattices connected only by chirality reversal combined with a mirror reflection. Full-wave simulations reveal mirror-related splitting of the two opposite-helicity branches in the band structure and isofrequency contours, with the channels exchanged when the ellipse orientation is reversed. Using a finite photonic crystal slab, we show that such splitting separates a linearly polarized beam into handedness-resolved channels, thus enabling beam splitting and direction-selective helicity filtering with target-helicity output fractions above 0.85 and output paths continuously tunable through the ellipse rotation angle. These results extend photonic altermagnetism to a previously unexplored lattice-symmetry class and establish mirror-symmetric chiral textures as building blocks for altermagnetism-inspired on-chip chiral photonics.

physics.optics↗

arXiv2026

Chips in the Flatland : 2D Semiconductors for Future Computing Electronic

As transistor scaling approaches its fundamental physical limits in the Angstrom era, two-dimensional (2D) semiconductors have emerged as the promising channel material candidates for future computing. While the device physics of 2D semiconductors have been rigorously explored, translating these nanodevices into fully functional integrated circuits remains a largely uncharted frontier. This review bridges the gap between material- and device-centric breakthroughs and circuit-level chip design in 2D semiconductors, a valley of death that has so far prevented translation of high-performance individual transistors into functional chips. We track the evolution of 2D semi-conductor field-effect transistors from basic Boolean logic families and standard cells to complex chip architectures, including recent milestones in RISC-V and monolithic CMOS microprocessors. Critically, we highlight the indispensable role of multiscale compact modeling, spanning semiclassical, quantum-hybrid and data-driven approaches, as the necessary link between device physics and the electronic design automation workflows for scalable chip development. By summarizing recent breakthroughs and identifying the bottlenecks in both fab and fabless trajectories of 2D semiconductors, this review shall provide insights that motivates the translation of proof-of-concept 2D transistors into fully functional computing chips, paving a way towards future Angstrom era computing technology empowered by 2D semiconductors.

physics.app-ph↗

arXiv2026

Tunable high-$Q$ Janus-to-chiral bound states in the continuum in bilayer PhCs

We propose a bilayer all-dielectric PhC for controlling Janus bound states in the continuum (BIC) and optical chirality through symmetry-selective perturbations. Starting from a symmetry-protected $\Gamma$-point BIC, we use interlayer displacement as one geometric control knob to generate different topological charges in the upward radiation and downward radiation channels. A subsequent diagonal in-plane displacement reconstructs the polarization topology around the BIC and generates a Janus-chiral BIC with strong handedness selectivity. In contrast, other in-plane perturbations generate chiral quasi-BICs with finite radiative coupling, for which the circular dichroism (CD) and resonance wavelength can be continuously tuned. We further show that material conductivity provides an additional dissipative degree of freedom for actively modulating the chiral response, with a switchable CD exceeding 0.89. Near-field optical-chirality distributions and multipole decompositions reveal that the chiral response originates from a symmetry-induced imbalance of local optical handedness and a spin-selective magnetic-dipole resonance. These results reveal the topological relationship between Janus radiation, polarization singularities and intrinsic chirality, thus paving a scalable route toward reconfigurable high-$Q$ chiral photonics.

physics.optics↗

arXiv2026

Ferroelectric Band Twinning from Pair-State Symmetry

Ferroelectric switching provides a nonvolatile way to control electronic structures, but a general symmetry rule connecting the full Bloch bands of two switchable polarization states is still lacking. Here, we introduce ferroelectric band twinning, a pair-state relation in which the bands of two opposite-polarization states are mapped onto each other by a non-inversion state-exchange symmetry. Using dichromatic groups, we derive the band-twinning rule and identify 11 ferroelectric band-twinning point-group classes. Screening the Ferroelectric Materials Database yields 16 candidate compounds, of which the two lattice-metric-preserving candidates, bulk gamma-Ag3SI and BaAl2O4, are selected for first-principles validation. For gamma-Ag3SI, we further show that the same pair-state symmetry controls the transformation of shift-current tensor components under polarization reversal. These results establish ferroelectric band twinning as a general symmetry framework for nonvolatile control of momentum-dependent electronic structures in ferroelectrics.

cond-mat.mtrl-sci↗

arXiv2025

Generalized Brillouin Zone Fragmentation

The Generalized Brillouin Zone (GBZ) encodes how lattice momentum is complex-deformed due to non-Hermitian skin accumulation, and has proved essential in restoring bulk-boundary correspondences. However, we find that generically, the GBZ is neither unique nor well-defined if more than one skin localization direction or strength exists, even in systems with no asymmetric hoppings. Instead, open boundary condition (OBC) eigenstates become complicated superpositions of multiple competing skin modes from "fragments" of all possible GBZs solutions. We develop a formalism that computes the fragmented GBZ in a scalable manner, with fragmentation extent quantified through our newly-defined composition IPR and spectral relative entropy. GBZ fragmentation is revealed to fundamentally challenge the notion of discontinuous phase transitions, since topological winding contributions from different GBZ fragments can "melt away" at different rates. Phenomenologically, GBZ fragmentation also leads to edge localization in all observables in energetically weighted ensembles such as thermal ensembles. This contrasts with conventional GBZs where the skin localization completely cancels in biorthogonal expectations. Occurring universally in multi-mode non-Hermitian media, as we concretely demonstrate with photonic crystal simulations, GBZ fragmentation points towards a new paradigm that is essential for understanding the band structure and the topological and dynamical properties of diverse generic non-Hermitian systems.

cond-mat.other↗

arXiv2025

Janus bound states in the continuum in structurally symmetric photonic crystals

We propose a sigma_z-symmetry-preserving approach to achieve Janus bound states in the continuum (Janus BICs) exhibiting asymmetric topological charges in the upward and downward radiation channels. While prior approaches typically involve explicit structural perturbations to break vertical symmetry, our design leverages a bilayer photonic crystal slab (PCS) system with independently tunable refractive indices, introducing an optical asymmetry without altering the geometric symmetry. In the optical symmetry case, the system supports symmetry-protected BICs at Gamma point with topological charge q = -1, and Friedrich-Wintgen BICs (FW-BICs) at off-Gamma point with q = +1. Upon introducing refractive index detuning, the polarization vortex splits into two circularly polarized states (C points) with half-integer topological charge (q = 1/2), shifting oppositely in momentum space for upward and downward radiation, while the symmetry-protected BICs remain unaffected. Janus BICs are established through the shift of upward-radiating C points shift towards the Gamma point, accumulating a total topological charge of q = -1, while the downward-radiating counterpart contributes q = +1, leading to a net topological charge reversal between the two radiation channels. This purely optical mechanism allows for the realization of Janus BICs without any structural deformation. Their asymmetric topological nature makes them ideally suited for applications in unidirectional light sources, chiral photonic interfaces, and topological photonic circuits, offering a promising platform for on-chip optical communication, sensing, and quantum information processing.

physics.optics↗

arXiv2023

Exceptional points in non-Hermitian Photonics: Applications and Recent Developments

Exceptional points are complex branching singularities of non-Hermitian bands that have lately attracted considerable interest, particularly in non-Hermitian photonics. In this article, we review some recent developments in non-Hermitian photonic platforms such as waveguides, photonic crystals, Fabry-Perot resonators and plasmonic systems, and suggest how optical non-linearities and exceptional bound states can significantly impact the development of non-Hermitian photonics in the near future.

physics.optics↗

arXiv2023

Experimental observation of exceptional bound states in a classical circuit network

Exceptional bound (EB) states represent an unique new class of robust bound states protected by the defectiveness of non-Hermitian exceptional points. Conceptually distinct from the more well-known topological states and non-Hermitian skin states, they were recently discovered as a novel source of negative entanglement entropy in the quantum entanglement context. Yet, EB states have been physically elusive, being originally interpreted as negative probability eigenstates of the propagator of non-Hermitian Fermi gases. In this work, we show that EB states are in fact far more ubiquitous, also arising robustly in broad classes of systems whether classical or quantum. This hinges crucially on a newly-discovered spectral flow that rigorously justifies the EB nature of small candidate lattice systems. As a highlight, we present their first experimental realization through an electrical circuit, where they manifest as prominent stable resonant voltage profiles. Our work brings a hitherto elusive but fundamentally distinctive quantum phenomenon into the realm of classical metamaterials, and provides a novel pathway for the engineering of robust modes in otherwise sensitive systems.

quant-ph↗

arXiv2022

Terahertz Polarization Conversion from Optical Dichroism in a Topological Dirac Semimetal

Topological Dirac semimetals (TDSM), such as Cd$_3$As$_2$ and Na$_3$Bi, exhibits strong optical dichroism with contrasting dielectric permittivity along different crystal axes. However, such optical dichroism is often overlooked in the study of TDSM-based optoelectronic devices, and whether such optical dichroism can lead to unique functionalities not found under the isotropic approximation remain an open question thus far. Here we show that the optical dischroism in TDSM lead to starkly different terahertz (THz) responses and device performance as compared to the isotropic case. Using finite-difference time-domain simulations of a Cd$_3$As$_2$-based metasurface, we demonstrate that such optical dichroism can lead to an unexpected THz wave polarization conversion even if the metasurface structure remains C$_4$ four-fold rotationally symmetric, a practically useful feature not achievable under the isotropic model of TDSM. Our findings concretely reveal the contrasting spectral response between isotropic and anisotropic media, and shed important light on the capability of anisotropic TDSM in THz applications, leading not just to the more accurate device modelling, but also a new route in realizing THz waves polarization conversion without the need of complex device morphology commonly employed in conventional polarization converters.

physics.optics↗

arXiv2022

Port Reconfigurable Phase-Change Optical Resonator

Active control and manipulation of electromagnetic waves are highly desirable for advanced photonic device technology, such as optical cloaking, active camouflage and information processing. Designing optical resonators with high ease-of-control and reconfigurability remains a open challenge thus far. Here we propose a novel mechanism to continuously reconfigure an optical resonator between one-port and two-port configurations via \emph{phase-change material} for efficient optical modulation. By incorporating a phase-change material VO$_2$ substrate into a photonic crystal optical resonator, we computationally show that the system behaves as a one-port device with near-perfect absorption and two-port device with high transmission up to 92% when VO$_2$ is in the metallic rutile phase and insulating monoclinic phase, respectively. The optical response can be continuously and reversibly modulated between various intermediate states. More importantly, the proposed device is compatible with wide-angle operation and is robust against structural distortion. Our findings reveal a novel device architecture of \emph{port reconfigurable} optical resonator uniquely enabled by switchable optical properties of phase change material.

physics.optics↗