Andreev and Single Particle Tunneling Spectroscopies in Underdoped Cuprates

TL;DR

This paper models tunneling spectroscopy in underdoped cuprates, explaining the coexistence of small and large energy gaps observed experimentally through a phenomenological approach.

Contribution

It introduces a theory that semi-quantitatively explains the two-gap behavior in tunneling spectra of underdoped cuprates.

Findings

Small energy gap observed in Andreev reflection in transparent tunneling.

Large energy gap observed in single particle tunneling in Giaever limit.

Theory aligns with experimental tunneling spectra observations.

Abstract

We study tunneling spectroscopy between a normal metal and underdoped cuprate superconductor modeled by a phenomenological theory in which the pseudogap is a precursor to the undoped Mott insulator. In the transparent tunneling limit, the spectra show a small energy gap associated with Andreev reflection. In the Giaever limit, the spectra show a large energy gap associated with single particle tunneling. Our theory semi-quantitatively describes the two gap behavior observed in tunneling experiments.