Anisotropy-driven quantum capacitance in multi-layered black phosphorus

TL;DR

This paper presents analytic results on quantum capacitance in multi-layered black phosphorus, demonstrating optical tuning via photon-dressing of dispersion and implications for FET performance and phase transitions.

Contribution

It introduces a theoretical framework for tuning quantum capacitance in black phosphorus using optical fields and dual gating, highlighting anisotropic effects and phase transition considerations.

Findings

Quantum capacitance is highly anisotropic in black phosphorus.

Photon-dressing enhances quantum capacitance and dispersion asymmetry.

Optical and electrostatic gating can tune phase transitions and thermoelectric properties.

Abstract

We report analytic results on quantum capacitance (C$_{q}$) measurements and their optical tuning in dual-gated device with potassium-doped multi-layered black phosphorous (BP) as the channel material. The two-dimensional (2D) layered BP is highly anisotropic with a semi-Dirac dispersion marked by linear and quadratic contributions. The C$_{q}$ calculations mirror this asymmetric arrangement. A further increase to the asymmetry and consequently C$_{q}$ is predicted by photon-dressing the BP dispersion. To achieve this and tune C$_{q}$ in a field-effect transistor (FET), we suggest a configuration wherein a pair of electrostatic (top) and optical (back) gates clamp a BP channel. The back gate shines an optical pulse to rearrange the dispersion of the 2D BP. Analytic calculations are done with Floquet Hamiltonians in the off-resonant regime. The value of such C$_{q}$ calculations, in addition, to its role in adjusting the current drive of an FET is discussed in context of metal-insulator and topological phase transitions and enhancements to the thermoelectric figure of merit.