Superconducting Fluctuation and Pseudogap in Disordered Short Coherence Length Superconductor

Abstract

We investigate the role of disorder on the superconducting (SC) fluctuation in short coherence length d-wave superconductors. The particular intetest is focused on the disorder-induced microscopic inhomogeneity of SC fluctuation and its effect on the pseudogap phenomena. We formulate the self-consistent 1-loop order theory for the SC fluctuation in inhomogeneous systems and analyze the disordered t-t ′ -V model. The SC correlation function, electronic DOS and the critical temperature are estimated. The SC fluctuation is localized like a nanoscale granular structure when the coherence length is short, namely the transition temperature is high. This is contrasted to the long coherence length superconductors where the order parameter is almost uniform in the microscopic scale. In the former case, the SC fluctuation is enhanced by the disorder in contrast to the Abrikosov-Gorkov theory. These results are consistent with the STM, NMR and transport measurements in high-Tc cuprates and illuminate the essential role of the microscopic inhomogeneity. We calculate the spacial dependence of DOS around the single impurity and discuss the consistency with the NMR measurements.

Random Spin–Orbit Coupling in Spin Triplet Superconductors: Stacking Faults in Sr2RuO4 and CePt3Si

“…A higher-order theory, such as the self-consistent T-matrix approximation, is needed for a quantitative estimation. (C) Highly two-dimensional regime W z < T c0 where the spatial inhomogeneity plays an important role like in short coherence length superconductors [48][49][50] In this regime the spatial average (replica symmetry) taken in the Born approximation as well as in the self-consistent T-matrix approximation is not justified. In the limit of two-dimensionality W z /T c0 → 0, the layers are independent of each other.…”

Disorder Effects on Competition between Antiferromagnetism and Superconductivity in Cuprate Superconductors through the Enhancement in Charge Susceptibility

“…In such a case, the SC state becomes robust against impurities in general. 51 Although electrons in cuprates experience a strong Coulomb repulsion, we have analyzed in the weak-coupling situation that U = 2t because the mean-field approximation gives a greatly overestimated T N for large-U regions. Our weak-coupling assumption can be justified to some extent by regarding U as an effective low-energy vertex function in the spin 25/32 channel.…”

Superconductivity in compensated and uncompensated semiconductors

“…We analyze the model of equation (1) on the basis of the real-space self-consistent T-matrix approximation (RSTA) which has been formulated to investigate the disordered d-wave superconductivity [44]. The calculation is carried out above T c , and the instability to the superconducting transition is investigated.…”

“…The thermal fluctuation of superconductivity is taken into account in the self-consistent 1-loop order. Although the fluctuation has been neglected in many microscopic investigations of the random systems [45][46][47], it plays an essential role in strongly disordered systems because the microscopic inhomogeneity enhances the fluctuations [10,44].…”