arXiv subjects

Yunjia Zhai

Publications and source records attributed to Yunjia Zhai.

4 recordsLinked to original sources

arXiv2026

Topological bound states in a lattice of rings with nearest-neighbour interactions

We study interaction-induced bound states in a system of ultracold bosons loaded into the states with orbital angular momentum in a one-dimensional staggered lattice of rings. We consider the hard-core limit and strong nearest-neighbour interactions such that two particles in next neighbouring sites are bound. Focusing on the manifold of such bound states, we have derived the corresponding effective model for doublons. With orbital angular momentum $l=1$, the original physical system is described as a Creutz ladder by using the circulations as a synthetic dimension, and the effective model obtained consists of two Su-Schrieffer-Heeger (SSH) chains and two Bose-Hubbard chains. Therefore, the system can exhibit topologically protected edge states. In a structure that alternates $l=1$ and $l=0$ states, the original system can be mapped to a diamond chain. In this case, the effective doublon model corresponds to a Creutz ladder with extra vertical hoppings between legs and can be mapped to two SSH chains if all the couplings in the original system are equal. Tuning spatially the amplitude of the couplings destroys the inversion symmetry of these SSH chains, but enables the appearance of multiple flat bands.

cond-mat.quant-gas↗

arXiv2026

Geometrical control of topology with orbital angular momentum modes

We study how the topological properties of a one-dimensional staggered lattice, loaded into states with orbital angular momentum $l=1$, can be controlled simply by tuning the relative angle between sites. The original system under consideration can be depicted as a Creutz ladder model when unwrapping the different state circulations in a synthetic dimension. Depending on the hopping strengths of the chain, different topological regimes may be accessed by changing the ladder angle, as determined by the value of the winding number of the chain. We analytically and numerically explore the different available regimes, and determine the number of topologically protected edge states that exist in each case. We also study the emergence of band inversion across topological transitions and show that it agrees with the winding number calculations, thus serving as an additional topological marker. Then, we propose a realistic experimental implementation in a photonic waveguide system, where the topological transition manifests as a sudden change of the behavior of the propagation of light in the system.

cond-mat.quant-gas↗

arXiv2023

Patterning by dynamically unstable spin-orbit-coupled Bose-Einstein condensates

In a two-dimensional atomic Bose-Einstein condensate, we demonstrate Rashba spin-orbit coupling can always introduce dynamical instability into specific zero-quasimomentum states in all parameter regimes. During the evolution of the zero-quasimomentum states, such spin-orbit-coupling-induced instability can fragment the states and lead to a dynamically patterning process. The features of formed patterns are identified from the symmetries of the Bogoliubov-de Gennes Hamiltonian. We show that spin-orbit-coupled Bose-Einstein condensates provide an interesting platform for the investigation of pattern formations.

cond-mat.quant-gas↗

arXiv2019

Non-Hermitian Weyl Semimetals: Non-Hermitian Skin Effect and non-Bloch Bulk-Boundary Correspondence

We investigate novel features of three dimensional non-Hermitian Weyl semimetals, paying special attention to its unconventional bulk-boundary correspondence. We use the non-Bloch Chern numbers as the tool to obtain the topological phase diagram, which is also confirmed by the energy spectra from our numerical results. It is shown that, in sharp contrast to Hermitian systems, the conventional (Bloch) bulk-boundary correspondence breaks down in non-Hermitian topological semimetals, which is caused by the non-Hermitian skin effect. We establish the non-Bloch bulk-boundary correspondence for non-Hermitian Weyl semimetals: the Fermi-arc edge modes are determined by the non-Bloch Chern number of the bulk bands. Moreover, these Fermi-arc edge modes can manifest as the unidirectional edge motion, and their signatures are consistent with the non-Bloch bulk-boundary correspondence. Our work establish the non-Bloch bulk-boundary correspondence for non-Hermitian topological semimetals.

cond-mat.mes-hall↗