Phase- and temperature-driven chiral topological superfluids on a honeycomb lattice.

The correlated spinful Haldane model exhibits rich topological phases consisting of chiral topological superfluids (TSFs) and topological spin density waves. However, most of previous studies mainly focus on the case with the fixed hopping phase or at zero temperature. In this paper, we study the attractive spinful Haldane model with arbitrary phase at finite temperature. The chiral TSFs with Chern numberC = 2 and 4 emerge driven by the phase and temperature. In particular, the temperature can drive aC = 2 topological superfluid from a trivial normal insulator phase at an appropriate interaction. The bulk topology of all TSFs is uncovered by the Wilson loop method, and confirmed by the responses of edge dislocations.

Nonlinear optical switch based on coherent perfect absorption.

Coherent perfect absorption (CPA) or reflection (CPR) are methods to realize the extreme manipulation on an optical field. We propose a scheme to operate a bistable switch with convertible CPA and/or CPR. Generally, CPA and CPR occur with different input-field phases. For example, CPA is realized when two input probe beams are in phase; instead, CPR is achieved when they are out of phase. In this scheme, a CPA state can be converted to a CPR state by an incoherent field although two input fields are in phase. When we use the incoherent field as a switching field, the CPA (CPR) state is treated as the closed (open) state. As a result, the switching efficiency can theoretically reach a maximum value, i.e., η = 1. In addition, the switch can be operated in the linear regime with a weak input field, and in the nonlinear or bistable regime with a strong input field. Moreover, the efficiency of the bistable switch is sensitively dependent on the input-field intensity. It provides a potential application of this work on sensitive optical detecting.

Quantum interference control of perfect photon absorption in a three-level atom-cavity system.

We propose a scheme for controlling coherent photon absorption by electromagnetically induced transparency (EIT) in a three-level atom-cavity system. Coherent perfect absorption (CPA) occurs when time-reversed symmetry of lasing process is obtained with the destructive interference at the cavity interfaces. The frequency range of CPA is generally dependent on the decay rates of the cavity mirrors. The smaller decay rate of the cavity mirror causes the wider frequency range of CPA, and the needed intensity of the probe fields is larger to satisfy CPA condition for a given frequency. Although Rabi frequency of the control laser has little effect on the frequency range of CPA, with EIT-type quantum interference, the CPA mode is tunable by the control laser. In addition, with the relative phase, the probe fields can be perfectly transmitted and/or reflected. Therefore, the system can be used as a controllable coherent perfect absorber or transmitter (reflector), and our work may have practical applications in optical logic devices.