The fate of quasiparticles in the superconducting state

TL;DR

This paper presents a method using Kramers--Kronig transformation to isolate quasiparticle properties in superconductors, enabling better understanding of their electrodynamic behavior by combining microwave and infrared data.

Contribution

It introduces a novel approach to extract intrinsic quasiparticle properties in superconductors by separating them from superfluid response using Kramers--Kronig transformation.

Findings

Successful separation of quasiparticle and superfluid responses

Unified analysis of microwave and infrared measurements

Enhanced understanding of quasiparticle behavior in cuprates

Abstract

Quasiparticle properties in the superconducting state are masked by the superfluid and are not directly accessible to infrared spectroscopy. We show how one can use a Kramers--Kronig transformation to separate the quasiparticle from superfluid response and extract intrinsic quasiparticle properties in the superconducting state. We also address the issue of a narrow quasiparticle peak observed in microwave measurements, and demonstrate how it can be combined with infrared measurements to obtain unified picture of electrodynamic properties of cuprate superconductors.