Dynamical Anisotropic Response of Black Phosphorus under Magnetic Field

TL;DR

This study investigates how magnetic fields influence the ultrafast anisotropic optical response of black phosphorus, revealing that while the anisotropy decreases with magnetic field, hot carrier effects remain similar, opening avenues for multi-field control.

Contribution

The paper provides the first detailed experimental analysis of black phosphorus's dynamical anisotropic optical properties under magnetic fields up to 9 T using ultrafast spectroscopy.

Findings

Anisotropic optical response decreases with increasing magnetic field.

Relaxation dynamics of photoexcited carriers are unaffected by magnetic field.

Magneto-optical conductivity explains the observed effects.

Abstract

Black phosphorus (BP) has emerged as a promising material candidate for next generation electronic and optoelectronic devices due to its high mobility, tunable band gap and highly anisotropic properties. In this work, polarization resolved ultrafast mid-infrared transient reflection spectroscopy measurements are performed to study the dynamical anisotropic optical properties of BP under magnetic fields up to 9 T. The relaxation dynamics of photoexcited carrier is found to be insensitive to the applied magnetic field due to the broadening of the Landau levels and large effective mass of carriers. While the anisotropic optical response of BP decreases with increasing magnetic field, its enhancement due to the excitation of hot carriers is similar to that without magnetic field. These experimental results can be well interpreted by the magneto-optical conductivity of the Landau levels of BP thin film, based on an effective k*p Hamiltonian and linear response theory. These findings suggest attractive possibilities of multi-dimensional controls of anisotropic response (AR) of BP with light, electric and magnetic field, which further introduces BP to the fantastic magnetic field sensitive applications.