Magnetic-field-induced insulating behavior in black phosphorus under pressure

TL;DR

This work probes out-of-plane magnetotransport in black phosphorus under finely tuned pressures up to 1.5 GPa to illuminate field-induced electronic phases in the quantum-limit regime. It identifies a semiconductor–semimetal transition between 1.1 and 1.3 GPa, with a pronounced, temperature-sensitive onset of insulating behavior in the semiconducting side and a low-field Shubnikov–de Haas signal appearing just after metallization at 1.3 GPa. The observed insulating tendencies near the transition, along with the low-doping SdH data and recent theory, support the scenario of an excitonic insulator phase induced by strong electron–hole correlations, making pressurized BP a practical platform for exploring field-induced electronic phase transitions at moderate magnetic fields below 9 T.

Abstract

We investigated the out-of-plane magnetoresistance of pressurized black phosphorus (BP) with a longitudinal field configuration. Despite the absence of the Lorentz force in the present configuration, we observed a significant enhancement of magnetoresistance marked with a clear onset field in both the semiconducting (1.1 GPa) and semimetallic (1.3 GPa) phases. The insulating behavior observed near the semiconductor-semimetal transitio pressure is possibly associated with emergence of an excitonic phase, which has been suggested in a recent theoretical study. BP under finely tuned pressure can be a candidate to realize the field-induced electronic phase transition in a moderate magnetic field below 9 T.

Figures (3)

• Figure 1: (a) Crystal structure of BP with crystal axes. (b) Typical setup of out-of-plane resistivity measurement using the four-probe method under pressure. $I$ and $V$ represent the current and voltage terminals attached to one side of a sample.
• Figure 2: (a) Temperature dependence of $\rho_b$ under pressures up to 1.5 GPa. The black and red broken curves represent the fitting curves assuming the Arrhenius model. (b) Pressure dependence of the intrinsic ($E_g^{\mathrm{intrinsic}}$) and impurity ($E_g^{\mathrm{impurity}}$) gaps deduced by Arrhenius fitting. The inset shows the field dependence of $\rho_b$ at 0.95 K measured sufficiently below the semiconductor-semimetal transition pressure.
• Figure 3: (a) Field dependence of $\rho_b$ at 1.1 GPa. The inset shows the log-log plot of $\rho_b$. The red arrow indicates the onset field of the resistivity increase. (b) Field dependence of $\rho_b$ at 1.3 GPa. The inset shows the second derivative of $\rho_b$ at 0.95 K. The black arrows represent the resistivity peaks caused by SdH oscillation, and the red arrow indicates the onset of field-induced insulating behavior.