9 research outputs found
Non-Hermitian Chiral Skin Effect
The interplay between non-Hermitian effects and topological insulators has
become a frontier of research in non-Hermitian physics. However, the existence
of a non-Hermitian skin effect for topological-protected edge states remains
controversial. In this paper, we discover an alternative form of the
non-Hermitian skin effect called the non-Hermitian chiral skin effect (NHCSE).
NHCSE is a non-Hermitian skin effect under periodic boundary condition rather
than open boundary condition. Specifically, the chiral modes of the NHCSE
localize around \textquotedblleft topological defects\textquotedblright
characterized by global dissipation rather than being confined to the system
boundaries. We show its detailed physical properties by taking the
non-Hermitian Haldane model as an example. As a result, the intrinsic mechanism
of the hybrid skin-topological effect in Chern insulators is fully understood
via NHCSE. Therefore, this progress will be helpful for solving the
controversial topic of hybrid skin-topological effect and thus benefit the
research on both non-Hermitian physics and topological quantum states
Nonlinear Bloch wave dynamics in photonic Aharonov–Bohm cages
We study the properties of nonlinear Bloch waves in a diamond chain waveguide lattice in the presence of a synthetic magnetic flux. In the linear limit, the lattice exhibits a completely flat (wavevector k-independent) band structure, resulting in perfect wave localization, known as Aharonov-Bohm caging. We find that in the presence of nonlinearity, the Bloch waves become sensitive to k, exhibiting bifurcations and instabilities. Performing numerical beam propagation simulations using the tight-binding model, we show how the instabilities can result in either the spontaneous or controlled formation of localized modes, which are immobile and remain pinned in place due to the synthetic magnetic flux. © 2021 Author(s
Properties of A Class of Topological Phase Transition
The properties of a class of topological quantum phase transition (TQPT) are
analyzed based on a model proposed by Haldane. We study the effect of finite
temperature on this phase transition. We have found that finite temperature
would drive this TQPT to be a crossover, while it is stable against the weak
short range interaction. When the interaction is strong enough, however, this
TQPT is unstable and other states would emerge. Then we investigate the effect
of the on-site energy in the original haldane model. The critical difference
between our TQPT and the topological phase transition in conventional quantum
Hall system is discussed. Finally, we discuss the potential application of our
analysis to a topological phase transition proposed in a realistic system.Comment: 7 pages, 7 figures. Accepted by Phys. Rev.
Periodic Instanton and Phase Transition in Quantum Tunneling of Spin Systems
The quantum-classical transitions of the escape rates in a uniaxial spin
model relevant to the molecular magnet MnAc and a biaxial anisotropic
ferromagnetic particle are investigated by applying the periodic instanton
method. The effective free energies are expanded around the top of the
potential barrier in analogy to Landau theory of phase transitions. We show
that the first-order transitions occur below the critical external magnetic
field for the uniaxial spin model and beyond the critical
anisotropy constant ratio for the biaxial ferromagnetic grains,
which are in good agreement with earlier works.Comment: 14 pages, revtex, 5 postscript figure
Nonlinear Bloch wave dynamics in photonic Aharonov–Bohm cages
Summarization: We study the properties of nonlinear Bloch waves in a diamond chain waveguide lattice in the presence of a synthetic magnetic flux. In the linear limit, the lattice exhibits a completely flat (wavevector k-independent) band structure, resulting in perfect wave localization, known as Aharonov–Bohm caging. We find that in the presence of nonlinearity, the Bloch waves become sensitive to k, exhibiting bifurcations and instabilities. Performing numerical beam propagation simulations using the tight-binding model, we show how the instabilities can result in either the spontaneous or controlled formation of localized modes, which are immobile and remain pinned in place due to the synthetic magnetic flux.Presented on: APL Photonic