Angle-resolved Landau spectrum of electrons and holes in bismuth

TL;DR

This study maps the angle-dependent Landau spectrum of electrons and holes in bismuth using Nernst quantum oscillations, compares it with a Dirac Hamiltonian model, and reveals new phenomena at high magnetic fields.

Contribution

It provides the first detailed angle-resolved Landau spectrum of bismuth and tests a Dirac Hamiltonian model against experimental data, clarifying the g-factor and spin polarization effects.

Findings

Good agreement between theory and experiment for all orientations

Confirmation of Dirac spectrum relevance for electron pockets

Detection of additional unexpected Nernst peaks

Abstract

In elemental bismuth, emptying the low-index Landau levels is accompanied by giant Nernst quantum oscillations. The Nernst response sharply peaks each time a Landau level intersects the chemical potential. By studying the evolution of these peaks when the field rotates in three perpendicular planes defined by three high-symmetry axes, we have mapped the angle-resolved Landau spectrum of the system up to 12 T. A theoretical model treating electrons at L point with an extended Dirac Hamiltonian is confronted with the experimentally-resolved spectrum. We obtain a set of theoretical parameters yielding a good but imperfect agreement between theory and experiment for all orientations of the magnetic field in space. The results confirm the relevance of the Dirac spectrum to the electron pockets and settle the longstanding uncertainty about the magnitude of the g-factor for holes. According to our analysis, a magnetic field exceeding 2.5 T applied along the bisectrix axis puts all carriers of the three electron pockets in their lowest($j=0$) spin-polarized Landau level. On top of this complex angle-dependent spectrum, experiment detects additional and unexpected Nernst peaks of unidentified origin.