Landau spectrum and twin boundaries of bismuth in the extreme quantum limit

TL;DR

This study maps the complex Landau spectrum of bismuth in the extreme quantum limit using angle-resolved Nernst effect measurements, revealing the influence of twin boundaries and tilted crystal domains on electronic properties.

Contribution

It provides the first detailed experimental and theoretical mapping of bismuth's Landau spectrum up to 28 T, clarifying the origin of additional spectral lines and the role of twin boundaries.

Findings

Landau spectrum matches theoretical models with parabolic holes and Dirac electrons.

Additional lines originate from hole Landau levels in tilted twin crystals.

Twin boundaries create reservoirs with different chemical potentials and carrier concentrations.

Abstract

The Landau spectrum of bismuth is complex and includes many angle-dependent lines in the extreme quantum limit. The adequacy of single-particle theory to describe this spectrum in detail has been an open issue. Here, we present a study of angle-resolved Nernst effect in bismuth, which maps the angle-resolved Landau spectrum for the entire solid angle up to 28 T. The experimental map is in good agreement with the results of a theoretical model with parabolic dispersion for holes and an extended Dirac Hamiltonian for electrons. The angular dependence of additional lines in the Landau spectrum allows to uncover the mystery of their origin. They correspond to the lines expected for the hole Landau levels in a secondary crystal tilted by 108 degrees, the angle between twinned crystals in bismuth. According to our results, the electron reservoirs of the two identical tilted crystals have different chemical potentials and carriers across the twin boundary have different concentrations. An exceptional feature of this junction is that it separates two electron-hole compensated reservoirs. The link between this edge singularity and the states wrapping a three-dimensional electron gas in the quantum limit emerges as an outstanding open question.