Phenomenological theories of the low-temperature pseudogap: Hall number, specific heat and Seebeck coefficient

TL;DR

This paper compares three phenomenological theories of the pseudogap in cuprates, analyzing their predictions for thermodynamic and transport properties, and discusses how experimental signatures like electron pockets could distinguish these models.

Contribution

It unifies three successful phenomenological models within a common formalism and links their predictions to specific experimental signatures, especially electron pockets and doping dependence.

Findings

Rapid rise in specific heat across the transition in all models.

Drop in Seebeck coefficient associated with the emergence of electron pockets.

Electron pockets appear before the critical doping p* and are sensitive to the van Hove singularity position.

Abstract

Since its experimental discovery, many phenomenological theories successfully reproduced the rapid rise from $p$ to $1+p$ found in the Hall number $n_H$ at the critical doping $p^*$ of the pseudogap in superconducting cuprates. Further comparison with experiments is now needed in order to narrow down candidates. In this paper, we consider three previously successful phenomenological theories in a unified formalism---an antiferromagnetic mean field (AF), a spiral incommensurate antiferromagnetic mean field (sAF), and the Yang-Rice-Zhang (YRZ) theory. We find a rapid rise in the specific heat and a rapid drop in the Seebeck coefficient for increasing doping across the transition in each of those models. The predicted rises and drops are locked, not to~$p^*$, but to the doping where anti-nodal electron pockets, characteristic of each model, appear at the Fermi surface shortly before~$p^*$. While such electron pockets are still to be found in experiments, we discuss how they could provide distinctive signatures for each model. We also show that the range of doping where those electron pockets would be found is strongly affected by the position of the van~Hove singularity.