Ambipolar quantum transport in few-layer black phosphorus

Abstract

We have investigated the quantum transport properties of high-mobility electrons and holes in atomically thin black phosphorus ambipolar devices. The two-dimensional hole system exhibits unambiguously the quantum Hall effect in a magnetic field up to 30 T, while the electron system shows clearly developing Hall plateaus at integer Landau level filling factors accompanied by ${R}_{xx}$ oscillations, signaling the onset of the quantum Hall effect. By bringing the spin-resolved Landau levels of the electron system to a coincidence, we determine an electron spin susceptibility to be ${\ensuremath{\chi}}_{se}={m}^{*}{g}^{*}=1.1\ifmmode\pm\else\textpm\fi{}0.03$, which, combined with the electron mass ${m}^{*}=0.39\phantom{\rule{0.16em}{0ex}}{m}_{0}$, yields a Land\'e $g$ factor ${g}^{*}=2.8\ifmmode\pm\else\textpm\fi{}0.2$. The enhancement of spin susceptibility in the black phosphorus two-dimensional electron system is around 50% compared with band susceptibility, which agrees well with various two-dimensional charge-carrier systems with weak spin-orbit coupling, suggesting the important role played by the exchange interaction.