Phase and Amplitude Fluctuation in High-T_c Superconductors: Formation of Gap Stripes Due to Lack of Electron-Hole Symmetry in Cuprate Oxides

Abstract

T_c in high-temperature superconductors seems well described by coherence of overall phase of the superconducting order parameter that is complex and fluctuates in space and time (thermal and quantum phase fluctuation). Above T≥T_c is the pseudogap phase, where one has a nonzero pairing gap without global phase coherence. If one were to define a meanfield BCS temperature, T_c⁰, where pairing susceptibility diverges—the so-called Thouless instability—then we show in this communication that if the system has no electron-hole symmetry, we obtain a nonuniform phase of stripes where the pairing gap develops a periodic amplitude modulation at T=T_c⁰. This suppresses the q=o mode instability at T=T_c⁰—i.e., the BCS instability.