Observation of the Yamaji effect in a cuprate superconductor

TL;DR

This paper reports the first observation of the Yamaji effect in a cuprate superconductor above the critical temperature, providing direct evidence of closed Fermi surface pockets in the pseudogap phase, which challenges existing notions of Fermi surface reconstruction.

Contribution

It presents the first detection of the Yamaji effect in a cuprate superconductor above $T_c$, revealing small closed Fermi surface pockets in the pseudogap state without translational symmetry breaking.

Findings

Observation of the Yamaji effect above $T_c$ in HgBa$_2$CuO$_{4+eta}$

Identification of small Fermi surface pockets (~1.3% of Brillouin zone)

Evidence against Fermi surface reconstruction via translational symmetry breaking

Abstract

The pseudogap state of high-$T_{\rm c}$ cuprates, known for its partial gapping of the Fermi surface above the superconducting transition temperature $T_{\rm c}$, is believed to hold the key to understanding the origin of Planckian relaxation and quantum criticality. However, the nature of the Fermi surface in the pseudogap state has remained a fundamental open question. Here, we report the observation of the Yamaji effect above $T_{\rm c}$ in the single layer cuprate HgBa$_2$CuO$_{4+\delta}$. This observation is direct evidence of closed Fermi surface pockets in the normal state of the pseudogap phase. The small size of the pockets determined from the Yamaji effect (occupying approximately $1.3\%$ of the Brillouin zone area) is all the more surprising given the absence of evidence for long-range broken translational symmetry that can reconstruct the Fermi-surface.