Non-Classical Longitudinal Magneto-Resistance in Anisotropic Black Phosphorus

TL;DR

This study reports anisotropic and non-monotonic longitudinal and transverse magneto-resistance in black phosphorus, revealing a significant positive LMR likely due to its anisotropic Fermi surface, under high magnetic fields.

Contribution

It provides the first detailed measurements of anisotropic magneto-resistance in black phosphorus, highlighting the non-classical behavior linked to its anisotropic electronic structure.

Findings

Observation of both transverse and longitudinal magneto-resistance.

Larger positive LMR than TMR above 32 T.

Strong anisotropy linked to Fermi surface anisotropy.

Abstract

Resistivity measurements of a few-layer black phosphorus (bP) crystal in parallel magnetic fields up to 45 T are reported as a function of the angle between the in-plane field and the source-drain (S-D) axis of the device. The crystallographic directions of the bP crystal were determined by Raman spectroscopy, with the zigzag axis found within 5{\deg} of the S-D axis, and the armchair axis in the orthogonal planar direction. A transverse magneto-resistance (TMR) as well as a classically-forbidden longitudinal magneto-resistance (LMR) are observed. Both are found to be strongly anisotropic and non-monotonic with increasing in-plane field. Surprisingly, the relative magnitude (in %) of the positive LMR is larger than the TMR above $\sim$32 T. Considering the known anisotropy of bP whose zigzag and armchair effective masses differ by a factor of approximately seven, our experiment strongly suggests this LMR to be a consequence of the anisotropic Fermi surface of bP.