Hong-Ya Xu
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View article: Special relativity effects on chaos and periodic orbits - a semianalytic approach
Special relativity effects on chaos and periodic orbits - a semianalytic approach Open
In the study of nonlinear dynamics and chaos, analytically solvable physical models are rare. We investigate the classical motion of a trapped relativistic particle, subject to an electric and a magnetic field. When the directions of the e…
View article: Observation of Quantized Klein Tunneling in a Dielectric Resonator Chain
Observation of Quantized Klein Tunneling in a Dielectric Resonator Chain Open
We present the first experimental observation of quantized Klein tunneling in a bounded Dirac system, implemented by a dimer chain of dielectric microwave resonators. Both the unusual quantized levels and corresponding spinor states hybrid…
View article: Symmetry dictated universal helicity redistribution of Dirac fermions in transport
Symmetry dictated universal helicity redistribution of Dirac fermions in transport Open
Helicity is a fundamental property of Dirac fermions. Yet, the general rule of how it changes in transport is still lacking. We uncover, theoretically, the universal spinor state transformation and consequently helicity redistribution rule…
View article: Klein scattering of spin-1 Dirac-Weyl wave and localized surface plasmon
Klein scattering of spin-1 Dirac-Weyl wave and localized surface plasmon Open
Localized surface plasmon and Klein tunneling resonances are two phenomena that were previously thought to be unrelated, where the former plays an important role in subwavelength optics while the latter is fundamental to relativistic quant…
View article: Pseudospin modulation in coupled graphene systems
Pseudospin modulation in coupled graphene systems Open
The ability to manipulate pseudospin can find applications in Dirac-material based spintronics. Unlike the transport of real spin that can be modulated by a magnetic field, some form of magnetization, or a spin-transfer torque, pseudospin …
View article: Anomalous in-gap edge states in two-dimensional pseudospin-1 Dirac insulators
Anomalous in-gap edge states in two-dimensional pseudospin-1 Dirac insulators Open
Quantum materials that host a flatband, such as pseudospin-1 lattices and magic-angle twisted bilayer graphene, can exhibit drastically new physical phenomena including unconventional superconductivity, orbital ferromagnetism, and Chern in…
View article: Scattering of Dirac electrons from a skyrmion: Emergence of robust skew scattering
Scattering of Dirac electrons from a skyrmion: Emergence of robust skew scattering Open
We study electron scattering from a closed magnetic structure embedded in the top surface of a topological insulator. Outside the structure there is a uniform layer of ferromagnetic insulators, leading to a positive effective mass for the …
View article: Scattering of Dirac electrons from a skyrmion: emergence of robust skew scattering
Scattering of Dirac electrons from a skyrmion: emergence of robust skew scattering Open
We study electron scattering from a closed magnetic structure embedded in the top surface of a topological insulator (TI). Outside the structure there is a uniform layer of ferromagnetic insulator (FMI), leading to a positive effective mas…
View article: Electrical confinement in a spectrum of two-dimensional Dirac materials with classically integrable, mixed, and chaotic dynamics
Electrical confinement in a spectrum of two-dimensional Dirac materials with classically integrable, mixed, and chaotic dynamics Open
An emergent class of two-dimensional Dirac materials is α-T_{3} lattices that can be realized by adding an atom at the center of each unit cell of a lattice with T_{3} symmetry. The interaction strength α between this atom and any of its n…
View article: Anomalous chiral edge states in spin-1 Dirac quantum dots
Anomalous chiral edge states in spin-1 Dirac quantum dots Open
We uncover an unexpected family of in-gap chiral edge states in noninverted spin-1 Dirac quantum dots. The system represents a topologically trivial confinement configuration where such edge states are not expected according to the convent…
View article: Quantization of massive Dirac billiards and unification of nonrelativistic and relativistic chiral quantum scars
Quantization of massive Dirac billiards and unification of nonrelativistic and relativistic chiral quantum scars Open
Quantum scars constitute one of the fundamental pillars in the traditional field of nonrelativistic quantum chaos. In relativistic quantum systems, chiral scars have been discovered recently whose wave functions concentrate on odd periodic…
View article: Chaos-based Berry phase detector
Chaos-based Berry phase detector Open
The geometric or Berry phase, a characteristic of quasiparticles, is\nfundamental to the underlying quantum materials. The discoveries of new\nmaterials at a rapid pace nowadays call for efficient detection of the Berry\nphase. Utilizing $…
View article: Can a photonic thermalization gap arise in disordered non-Hermitian Hamiltonian systems?
Can a photonic thermalization gap arise in disordered non-Hermitian Hamiltonian systems? Open
The phenomenon of chiral-symmetry protected thermalization gap in Hermitian photonic systems is counterintuitive as it implies that the photon coherence can be continuously improved by disorders towards an asymptotic limit. We show that th…
View article: Phase locking of a pair of nano ferromagnetic oscillators on a topological insulator
Phase locking of a pair of nano ferromagnetic oscillators on a topological insulator Open
We investigate the magnetization dynamics of a pair of ferromagnetic insulators (FMIs) deposited on the surface of a topological insulator (TI). Due to the nonlinear nature of the underlying physics and intrinsic dynamics, the FMIs can exh…
View article: Decay of semiclassical massless Dirac fermions from integrable and chaotic cavities
Decay of semiclassical massless Dirac fermions from integrable and chaotic cavities Open
Conventional microlasing of electromagnetic waves requires (1) a high $Q$\ncavity and (2) a mechanism for directional emission. Previous theoretical and\nexperimental work demonstrated that the two requirements can be met with\ndeformed di…
View article: Relativistic quantum chaos—An emergent interdisciplinary field
Relativistic quantum chaos—An emergent interdisciplinary field Open
Quantum chaos is referred to as the study of quantum manifestations or fingerprints of classical chaos. A vast majority of the studies were for nonrelativistic quantum systems described by the Schrödinger equation. Recent years have witnes…
View article: Chaos in Dirac Electron Optics: Emergence of a Relativistic Quantum Chimera
Chaos in Dirac Electron Optics: Emergence of a Relativistic Quantum Chimera Open
We uncover a remarkable quantum scattering phenomenon in two-dimensional Dirac material systems where the manifestations of both classically integrable and chaotic dynamics emerge simultaneously and are electrically controllable. The disti…
View article: Nonequilibrium transport in the pseudospin-1 Dirac-Weyl system
Nonequilibrium transport in the pseudospin-1 Dirac-Weyl system Open
Recently, solid state materials hosting pseudospin-1 quasiparticles have attracted a great deal of attention. In these materials, the energy band contains a pair of Dirac cones and a flatband through the connecting point of the cones. As t…
View article: Superscattering of a pseudospin-1 wave in a photonic lattice
Superscattering of a pseudospin-1 wave in a photonic lattice Open
We uncover a superscattering behavior of pseudospin-1 wave from weak scatterers in the subwavelength regime where the scatterer size is much smaller than wavelength. The phenomenon manifests itself as unusually strong scattering characteri…
View article: Gaussian orthogonal ensemble statistics in graphene billiards with the shape of classically integrable billiards
Gaussian orthogonal ensemble statistics in graphene billiards with the shape of classically integrable billiards Open
A crucial result in quantum chaos, which has been established for a long time, is that the spectral properties of classically integrable systems generically are described by Poisson statistics, whereas those of time-reversal symmetric, cla…
View article: Nonlinear dynamics induced anomalous Hall effect in topological insulators
Nonlinear dynamics induced anomalous Hall effect in topological insulators Open
We uncover an alternative mechanism for anomalous Hall effect. In particular, we investigate the magnetisation dynamics of an insulating ferromagnet (FM) deposited on the surface of a three-dimensional topological insulator (TI), subject t…