Photoinduced pseudospin effects in silicene beyond the off-resonant condition

Abstract

We study the photoinduced manipulation of charge carriers in monolayer silicene subject to intense electromagnetic terahertz radiation. Considering the Dirac cone approximation and going beyond the off-resonant condition for large frequencies of the radiation field, where only virtual photon processes are allowed, we present the exact zero-momentum pseudospin polarization and numerical results for the quasienergy band structure and time-averaged density of states. We find that resonant processes, due to real photon emission and absorbtion processes, induce a band inversion that qualitatively modifies the quasienergy spectrum. These band-structure changes manifest themselves as an inversion of the averaged pseudospin polarization. Through the analysis of the time-averaged density of states we find that effective photoinduced gap manipulation can only be achieved in the intermediate and strong matter-radiation coupling regime where the off-resonant approximation breaks down.

Photo-modulation of the spin Hall conductivity of mono-layer transition metal dichalcogenides

“…Interestingly, this dispersion, as shown in Ref. 5 can be modulated by light under off-resonant conditions 6 to give rise to a valley-dependent tuning of the band gap and an overall alteration of the carrier transport characteristics.…”

“…The offresonant condition which is a non-equilibrium state happens when energy of the incoming radiation is much larger than the hopping amplitude of the electrons ( ω ≫ t); for such a case real photon absorption is inhibited by energy conservation, instead second order virtual photon emission or absorption occurs leading to reordering of electronic bands and photon-dressed eigen-states. 6,9 We theoretically calculate the SHC within the linear response framework for such a system and in presence of surface disorder to gauge the magnitude of the spin current. As we show later, the SHC declines as the frequency of the incoming radiation is raised or the intensity is lowered.…”

Photoinduced Pseudospin Dynamical Effects in Graphene-Like Systems

“…One could further explore the dynamical features at finite momentum but refer the reader to Ref. [35] where it is proven that the intermediate lightmatter-coupling regime is the physically correct scenario for describing the emergent topological features such as the realization of the single-valley polarized state in silicene. Needless to say that other quantities of interest such as charge and spin currents can be treated within the approximate scenarios discussed in the chapter, they go beyond the main interest of the chapter and are thus not further discussed here.…”

“…Here, we show that the quasi-energy spectrum presents a leveldependent photoinduced gap and we also show that coherent Landau level states can be synchronized in order to produce Rabi oscillations and quantum revivals [27]. In Section 3, we describe how the energy spectrum and pseudospin polarization in monolayer silicene [28][29][30][31][32][33] can be manipulated beyond the so-called off-resonant regime [34,35] when strong radiation effects are taken into account [36][37][38]. We find the explicit and realistic parameter regime for the realization of a single-valley polarized state in silicene.…”

Localization length versus level repulsion in one-dimensional driven disordered quantum wires

“…Coherent control through time-dependent periodic external fields is an exciting field in condensed matter physics with promising applications in many different areas like quantum transport [1][2][3][4][5][6][7] , spintronics 8,9 , control of many-body phases [10][11][12] and topological properties [13][14][15][16][17][18] . Some of its guiding principles have already been demonstrated experimentally in different setups [19][20][21][22][23] .…”