In this work, we study the effect of PT -symmetric complex potentials on the transport properties of one non-Hermitian system, which is formed by the coupling between a triple-quantum-dot molecule and two semi-infinite leads. As a result, it is found that the PT -symmetric imaginary potentials take pronounced effects on transport properties of such a system, including changes from antiresonance to resonance, shift of antiresonance, and occurrence of new antiresonance, which are determined by the interdot and dot-lead coupling manners. This study can be helpful in understanding the quantum transport behaviors modified by the PT symmetry in non-Hermitian discrete systems.
The band structure and topological properties of a 1D rhombus lattice are studied by defining three models according to the manners of intracell hopping amplitudes. Results show that in the presence of uniform intracell hopping amplitudes, degenerate topological edge states appear at the ends of the lattice. When the intracell hopping amplitudes change, the edge states change in different ways, but they are robust to a small amount of disorder. The inversion symmetry breaking modifies the degeneracy of the edge states and makes the edge states localized at one end of the lattice. Next, when local magnetic flux is introduced, the band structures of the three models are further modulated. New gaps can be opened and edge states can be induced with their different topological properties. This rhombus lattice can be a promising candidate for studying the edge states and their dependence on structural parameters and magnetic flux in 1D systems.
By introducing the next-nearest-neighboring (NNN) intersite coupling, we investigate the eigenenergies of the PT -symmetric non-Hermitian Su-Schrieffer-Heeger (SSH) model with two conjugated imaginary potentials at the end sites. It is found that with the strengthening of NNN coupling, the particle-hole symmetry is destroyed. As a result, the bonding band is first narrowed and then undergoes the top-bottom reversal followed by the its width's increase, whereas the antibonding band is widened monotonously. In this process, the topological state extends into the topologically-trivial region, and its energy departs from the energy zero point, accompanied by the emergence of one new topological state in this region. All these results give rise to the complication of the topological properties and the manner of PT -symmetry breaking. It can be concluded that the NNN coupling takes important effects to the change of the topological properties of the non-Hermitian SSH system.
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