Non-Hermitian Aubry-André-Harper model with short- and long-range p-wave pairing

Abstract: We investigate a non-Hermitian Aubry-Andr\'e-Harper model with short-range, as well as long-range p-wave pairing. Here, the non-Hermiticity is introduced through the onsite potential. A comprehensive analysis of several critical aspects of this system is conducted, which includes eigenspectra, topological properties, localization properties, and the transition from real to complex energies. Specifically, we observe the emergence of Majorana zero modes in the case of short-range pairing, whereas massive Dirac modes emerge in the case of long-range pairing. More importantly, for the case of short-range pairing, we observe two simultaneous phase transitions or double phase transitions: topological and multifractal to localized phase. On the other hand, in the case of the long-range pairing, the topological and multifractal to localized transitions do not coincide. However, for both ranges of pairing, we identify a double phase transition where delocalized (or metallic) to a critical multifractal state is accompanied by an unconventional shift from real to complex energies. Unlike the short-range pairing case, we observe mobility edges in the long-range pairing case.