Interband spectroscopy of Landau levels and magnetoexcitons in bulk black phosphorus

TL;DR

This study investigates the magneto-optical properties of bulk black phosphorus at high magnetic fields, revealing Landau levels, Zeeman splitting, and magnetoexcitons, providing insights into its electronic structure and excitonic effects.

Contribution

It presents the first high-field magneto-optical spectroscopy of bulk black phosphorus, identifying Landau levels, Zeeman splitting, and magnetoexcitons, and estimating key electronic parameters.

Findings

Observation of Landau levels up to n=6 with linear B dependence.

Determination of electron-hole reduced mass as 0.13 m_0.

Identification of magnetoexciton peaks with quadratic B shift and binding energy of 9.7 meV.

Abstract

Low-dimensional systems based on black phosphorus (BP) have recently attracted much interest. Since the crystal structure of BP consists of 2D layers with a strong in-plane anisotropy, its electronic properties at a high magnetic field ($B$) are quite interesting. Here, we report a magneto-optical study of bulk BP at high $B$ to 12 T perpendicular to the 2D layers. In the obtained optical conductivity spectra, periodic peaks are clearly observed corresponding to Landau levels of up to $n$=6 quantum number. They exhibit almost linear shifts with $B$, and from their analysis an electron-hole reduced mass of 0.13 $m_0$ is obtained, where $m_0$ is the electron mass. Many of the peaks appear in pairs, which is interpreted in terms of Zeeman splitting and an electron-hole combined $g$-factor of 6.6 is obtained. In addition, magnetoexciton peaks are observed to shift quadratically with $B$, and the exciton binding energy at $B$=0 is estimated to be 9.7 meV.