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Description
Black Phosphorous (BP) represents a very unique two dimensional (2D) material due to its tunable infrared band gap and its anisotropic conduction properties. It has been emerged as an attractive material with a huge potential for future nanoelectronics and nanophotonic applications [1]. BP also shows the optical signatures of pressure induced Lifshitz transition from a semiconductor to a Dirac semi-metal due to emergence of a plasma of massless charge carriers [2]. Here we investigate the nonlinear terahertz (THz) electrodynamics of black phosphorus along the more conducting armchair direction. The THz saturable-absorption properties of black phosphorus can be understood within a thermodynamic model by assuming a fast thermalization of the electron bath which is similar to the case of other 2D systems such as graphene and topological insulators [3]. Our analysis shows that although BP does not show the presence of massless fermions at ambient pressure and temperature, its anomalous THz nonlinear properties can be accounted for by a relativistic massive Dirac dispersion, provided that the Fermi temperature is low enough. This suggests that an optimal tuning of the Fermi level could be a strategy to engineer a strong THz nonlinear response in other massive Dirac materials, such as transition-metal dichalcogenides or high-temperature superconductors.
References:
1. R. Fei et al., Topologically protected Dirac cones in compressed bulk black phosphorus, Phys. Rev. B 91 (2015) 195319.
2. P. Di Pietro et al., Emergent Dirac carriers across a pressure-induced Lifshitz transition in black phosphorus, Phys. Rev. B 98 (2018) 165111.
3. N. Adhlakha et al., Terahertz saturable absorption from relativistic high-temperature thermodynamics in black phosphorus, Phys. Rev. Appl. 20 (2023) 054039.
| Scientific Topics | Solid State Physics |
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