Non-Hermitian Floquet topological phases with arbitrarily many real-quasienergy edge states

Topological states of matter in non-Hermitian systems have attracted a lot of attention due to their intriguing dynamical and transport properties. In this paper, we propose a periodically driven non-Hermitian lattice model in one dimension, which features rich Floquet topological phases. The topological phase diagram of the model is derived analytically. Each of its non-Hermitian Floquet topological phases is characterized by a pair of integer winding numbers, counting the number of real zero- and π-quasienergy edge states at the boundaries of the lattice. Non-Hermiticity-induced Floquet topological phases with unlimited winding numbers are found, which allow arbitrarily many real zero- and π-quasienergy edge states to appear in the complex quasienergy bulk gaps in a well-controlled manner. We further suggest probing the topological winding numbers of the system by dynamically imaging the stroboscopic spin textures of its bulk states.