Current-enabled optical conductivity of superconductors

Abstract

While optical techniques are fundamental in the investigation of the superconducting state, in many clean superconductors the combination of particle-hole and inversion symmetries prevents momentum-conserving transitions. Here, the authors show that by driving supercurrent through the sample optical transitions across the superconducting gap become allowed even in clean single-band systems. As the signal depends strongly on the superconducting pairing as well as on the underlying normal state, supercurrent-driven optical conductivity provides a new way of determining the superconducting state properties.