Electronic properties of phosphorene in out-of-equilibrium conditions.
Manghi F., Bonacci M., Puviani M.
II - Fisica della materia
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2-Dimensional (2D) materials are a class of nanomaterials that are one -- or very few -- atom thick. The main actor in this field has been graphene whose extraordinary properties are intimately related to its reduced dimensionality. The types of 2D materials keep increasing and include now insulators, semiconductors and semimetals. Among them, phosphorene is one of the most interesting post-graphene materials. Phosphorene is a single sheet of black phosphorus, and, in analogy with graphene, it can be obtained by mechanical exfoliation. One of the advantages of phosphorene with respect to graphene is the presence of a band gap, an essential feature in view of device applications. In this paper we study the effects that intense laser fields may have on the electronic states of phosphorene. The discovery that circularly polarized light may induce non-trivial topological behavior in materials that would be standard in static conditions has opened the way to the realization of the so-called Floquet topological insulators, where a topological phase may be engineered and manipulated by tunable controls such as polarization, periodicity and amplitude of the external perturbation. Based on a solution of the Floquet Hamiltonian we have studied the photon-renormalized electronic states in phosphorene and phosphorene nanoribbons driven out of equilibrium by time-dependent electromagnetic fields in different regimes of intensity, polarization and frequency. We have considered different thicknesses and various nanoribbon configurations, looking for non-trivial topological phase formation and the presence of protected edge states. We show in particular that while for a single phosphorene layer these protected states do exist in a given regime of field polarization, frequency and intensity, this is no longer true when more phosphorene sheets are stacked to give rise to thicker structures.