Normal state Nernst effect from bi-directional bond density wave state in high T_c cuprates

TL;DR

This paper investigates how a bi-directional bond density wave state in high T_c cuprates influences the Fermi surface and Nernst effect, providing insights into charge order phenomena in underdoped superconductors.

Contribution

It models a bi-directional BDW state with a d-wave form factor and calculates its impact on Fermi surface topology and Nernst coefficient, aligning with experimental observations.

Findings

Fermi surface features electron and hole pockets in the BDW phase.

Low temperature Nernst coefficient becomes negative in the presence of BDW.

Results match experimental data on charge order effects in cuprates.

Abstract

The role of charge order in the phase diagram of high temperature cuprate superconductors has been recently re-emphasized by the experimental discovery of an incipient bi-directional charge density wave (CDW) phase in a class of underdoped cuprates. In a subset of the experiments, the CDW has been found to be accompanied by a d-wave intra-unit-cell form factor, indicating modulation of charge density on the oxygen orbitals sandwiched between neighboring Cu atoms on the CuO planes (the so-called bond-density wave (BDW) phase). Here we take a mean field Q_1=(2\pi/3,0) and Q_2=(0,2\pi/3) bi-directional BDW phase with a d-wave form factor, which closely resembles the experimentally observed charge ordered states in underdoped cuprates, and calculate the Fermi surface topology and the resulting quasiparticle Nernst coefficient as a function of temperature and doping. We establish that, in the appropriate doping ranges where the low temperature phase (in the absence of superconductivity) is a BDW, the Fermi surface consists of an electron and a hole pocket, resulting in a low temperature negative Nernst coefficient as observed in experiments.