Signatures of superconducting gap inhomogeneities in optical properties
Abstract
Scanning tunneling spectroscopy applied to the high- Tc cuprates has revealed significant spatial inhomogeneity on the nanoscale. Regions on the order of a coherence length in size show variations of the magnitude of the superconducting gap of order ±20% or more. An important unresolved question is whether or not these variations are also present in the bulk, and how they influence superconducting properties. As many theories and data analyses for high- Tc superconductivity assume spatial homogeneity of the gap magnitude, this is a pressing question. We consider the far-infrared optical conductivity and evaluate, within an effective-medium approximation, what signatures of spatial variations in gap magnitude are present in various optical quantities. In addition to the case of d -wave superconductivity, relevant to the high- Tc cuprates, we have also considered s -wave gap symmetry in order to provide expected signatures of inhomogeneities for superconductors in general. While signatures of gap inhomogeneities can be strongly manifested in s -wave superconductors, we find that the far-infrared optical conductivity in d -wave is robust against such inhomogeneity, such that any changes maintain the character of a curve for a single d -wave gap.
- Publication:
-
Physical Review B
- Pub Date:
- September 2008
- DOI:
- 10.1103/PhysRevB.78.094513
- arXiv:
- arXiv:0806.2131
- Bibcode:
- 2008PhRvB..78i4513L
- Keywords:
-
- 74.25.Gz;
- 74.72.-h;
- 74.40.+k;
- Optical properties;
- Cuprate superconductors;
- Fluctuations;
- Condensed Matter - Superconductivity;
- Condensed Matter - Strongly Correlated Electrons
- E-Print:
- 8 pages, 7 figures