Thematic Unit of Excellence on Computational Materials Science
S. N. Bose National Centre for basic Sciences

Strong disorder in strongly correlated matter: Perspective from cuprates

: Dr. Amit Ghosal
  , Indian Institute of Science Education and Research, Kolkata,

: Tuesday, 16th August, 2015
: 11:30 AM
: Fermion (LH-3)
: Strong disorder in strongly correlated matter: Perspective from cuprates

Abstract: The effect of potential impurities on cuprate superconductors will be discussed using a formalism suitable for addressing the complex interplay of the bare repulsive electronic correlations and disorder, both being strong. We show that the mechanism governing the demise of superconductivity is rather subtle and differs from conventional descriptions. While the superconductivity remains surprisingly robust for up to a moderate disorder, it crashes down sharply at strong disorders. The initial robustness is attributed to the repulsive correlations that smear out charge inhomogeneities by self-consistently reorganizing the hopping on the bonds. Such reorganization prohibits the formation of superconducting 'islands'. The merit of a simple minded pairing theory, similar to that of Anderson for disordered conventional superconductors, will be discussed in order to develop deeper understanding of the results up to moderate disorder strengths. With increasing strength of disorder, however, the potential difference across some bonds reach of the order of bandwidth and the system prefers prohibiting hopping on such links. Integrating this concept within our formalism, we show that the correlations fail to homogenize the system across these 'cut-bonds'. This produces locally Mott-insulating, Anderson-insulating, as well as superconducting regions interspersed among each other at strong disorder, eventually destroying the global superconductivity..