Microscopic approach to high-temperature superconductors: Pseudogap phase

TL;DR

This paper presents a microscopic theoretical approach using the PRM scheme to understand the pseudogap phase in high-temperature superconductors, aligning well with ARPES experimental data and shedding light on the pseudogap's origin.

Contribution

It introduces a novel renormalization scheme (PRM) applied to the $t$-$J$ model to analyze the pseudogap phase microscopically, providing insights into spectral features.

Findings

ARPES spectral function matches experimental observations

Well-defined peaks near the Fermi energy in the nodal direction

Pseudogap arises from suppression of incoherent spectral weight

Abstract

Despite the intense theoretical and experimental effort, an understanding of the superconducting pairing mechanism of the high-temperature superconductors is still lacking. An additional puzzle is the unknown connection between the superconducting gap and the so-called pseudogap which is a central property of the most unusual normal state. Angle-resolved photoemission spectroscopy (ARPES) measurements have revealed a gap-like behavior on parts of the Fermi surface, leaving a non-gapped segment known as Fermi arc around the diagonal of the Brillouin zone. Starting from the $t$-$J$ model, in this paper we present a microscopic approach to investigate physical properties of the pseudogap phase in the framework of a novel renormalization scheme called PRM. This approach is based on a stepwise elimination of high-energy transitions using unitary transformations. We arrive at a renormalized 'free' Hamiltonian for correlated electrons. The ARPES spectral function along the Fermi surface turns out to be in good agreement with experiment: We find well-defined excitation peaks around $\omega=0$ near the nodal direction, which become strongly suppressed around the antinodal point. The origin of the pseudogap can be traced back to a suppression of spectral weight from incoherent excitations in a small $\omega$-range around the Fermi energy. In a subsequent paper, also the supercunducting phase at moderate hole doping will be discussed within the PRM approach.