Unconventional temperature dependence of the cuprate excitation spectrum

TL;DR

This paper models the temperature-dependent electronic density of states in cuprates, revealing a pseudogap above the critical temperature due to excited Cooper pairs, and explores the effects of magnetic fields and doping levels.

Contribution

It introduces a novel Bose-like condensation model to explain the pseudogap phenomena and the temperature dependence of the DOS in cuprates.

Findings

Pseudogap persists above $T_c$ due to excited pairs.

Normal DOS is recovered at the pair formation temperature $T^*$.

DOS shape depends on combined bosonic and fermionic excitations.

Abstract

Key properties of the cuprates, such as the pseudogap observed above the critical temperature $T_c$, remain highly debated. Given their importance, we recently proposed a novel mechanism based on the Bose-like condensation of mutually interacting Cooper pairs [W. Sacks, A. Mauger, Y. Noat, Superconduct. Sci. Technol. 28 105014, (2015)]. In this work, we calculate the temperature dependent DOS using this model for different doping levels from underdoped to overdoped. In all situations, due to the presence of excited pairs, a pseudogap is found above $T_c$ while the normal DOS is recovered at $T^*$, the pair formation temperature. A similar behavior is found as a function of magnetic field, crossing a vortex, where a pseudogap exists in the vortex core. We show that the precise DOS shape depends on combined pair (boson) and quasiparticle (fermion) excitations, allowing for a deeper understanding of the SC to the PG transition.