Quantum Oscillations in Cu$_x$Bi$_2$Se$_3$ in High Magnetic Fields

TL;DR

This study investigates quantum oscillations in Cu$_x$Bi$_2$Se$_3$ under high magnetic fields, revealing Fermi surface shape changes and a possible Lifshitz transition, contributing to understanding its normal state electronic properties.

Contribution

It provides detailed analysis of quantum oscillations and Fermi surface evolution in Cu$_x$Bi$_2$Se$_3$, highlighting a potential Lifshitz transition with high magnetic field data.

Findings

Fermi surface transforms from 3D to quasi-cylindrical with doping

Quantum oscillation period follows ellipsoidal Fermi surface prediction

Possible Lifshitz transition identified at high carrier density

Abstract

Cu$_x$Bi$_2$Se$_3$ has drawn much attention as the leading candidate to be the first topological superconductor and the realization of coveted Majorana particles in a condensed matter system. However, there has been increasing controversy about the nature of its superconducting phase. This study sheds light on present ambiguity in the normal state electronic state, by providing a complete look at the quantum oscillations in magnetization in Cu$_x$Bi$_2$Se$_3$ at intense high fields up to 31T. Our study focuses on the angular dependence of the quantum oscillation pattern in a low carrier concentration. As magnetic field tilts from along the crystalline c-axis to ab-plane, the change of the oscillation period follows the prediction of the ellipsoidal Fermi surface. As the doping level changes, the 3D Fermi surface is found to transform into quasi-cylindrical at high carrier density. Such a transition is potentially a Lifshitz transition of the electronic state in Cu$_x$Bi$_2$Se$_3$.