Interplay of non-Hermitian skin effects and Anderson localization in nonreciprocal quasiperiodic lattices

Non-Hermiticity from nonreciprocal hoppings has been shown recently to demonstrate the non-Hermitian skin effect (NHSE) under open boundary conditions (OBCs). Here we study the interplay of this effect and the Anderson localization (AL) in a nonreciprocal quasiperiodic lattice, dubbed nonreciprocal Aubry-André model, and a rescaled transition point is exactly proved. The nonreciprocity can induce not only NHSEs but also the asymmetry in localized states, characterized by two Lyapunov exponents. Meanwhile, this transition is also topological, in the sense of a winding number associated with complex eigenenergies under periodic boundary conditions (PBCs), establishing a bulk-bulk correspondence. This interplay can be realized straightforwardly by an electrical circuit with only linear passive RLC components instead of elusive nonreciprocal ones, showing the transport of a continuous wave undergoes a transition between insulating and amplifying. This paradigmatic scheme can be immediately accessed in experiments even for more nonreciprocal models and will definitely inspire the study of interplay of NHSEs and ALs as well as more other quantum/topological phenomena in various systems.