arXiv subjects

Shuncai Zhao

Publications and source records attributed to Shuncai Zhao.

3 recordsLinked to original sources

arXiv2026

Left handness in a four-level atomic system

A scheme is proposed for realizing simultaneous negative permittivity and negative permeability based on quantum coherence in a four-level dense atomic system here.Under some parametric conditions the system shows that simultaneous negative permittivity and negative permeability(i.e.Left handness) can be achieved in a wider frequency band because of quantum coherence.And the novelty properties of gain and dispersion near the resonance frequency may have some potential applications.

quant-ph↗

arXiv2024

Zero absorption and large negative refractive index in a left-handed four-level atomic media

In this paper,we have investigated three external fields interacting with the four-level atomic system described by the density-matrix approach.The atomic system exhibits left-handedness with zero absorption as well as large negative refractive index.Varying the parameters of the three external fields,the properties of zero absorption,large negative refractive index from the atomic system keep unvarying.Our scheme proposes an approach to obtain negative refractive medium with zero absorption. The zero absorption property of atomic system may be used to amplify the evanescent waves that have been lost in the imaging by traditional lenses.And a slab fabricated by the left-handed atomic system may be an ideal candidate for designing perfect lenses.

quant-ph↗

arXiv2023

From orthogonal link to phase vortex in generalized dynamical Hopf insulators

In the creation of Hopf topological matters, the old paradigm is to conceive the Hopf invariant first, and then display its intuitive topology through links. Here we brush aside this effort and put forward a new recipe for unraveling the quenched two-dimensional (2D) two-band Chern insulators under a parallel quench protocol, which implies that the quench quantities with different momentum k are parallel or antiparallel to each other. We find that whether the dynamical Hopf invariant exists or not, the links in (2+1)D space always keep their standard shape even for topological initial states, and trace out the trajectories of phase vortices. The linking number is exactly equal to the difference between pre- and post-quench Chern numbers regardless of the construction of homotopy groups. We employ two concrete examples to illustrate these results, highlighting the polarity reversal at fixed points.

cond-mat.str-el↗