Plasmon-phonon coupling in a valley-spin-polarized two-dimensional electron system: A theoretical study on monolayer silicene

Abstract

We study the hybrid excitations due to the coupling between surface optical phonons of a polar insulator substrate and plasmons in the valley-spin-polarized metal phase of silicene under an exchange field. We perform the calculations within the generalized random-phase approximation where the plasmon-phonon coupling is taken into account by the long-range Fröhlich interaction. Our investigation on two hybridized plasmon branches in different spin and valley subbands shows distinct behavior compared to the uncoupled case. Interestingly, in one valley, it is found that while the high energy hybrid branch is totally damped in the spin-up state, it can be well-defined in the the spin-down state. Moreover, we show that the electron-phonon coupling is stronger in both spin-down subbands, regardless of valley index, due to their higher electron densities. In addition, we study the effects of electron-phonon coupling on the quasiparticle scattering rate of four distinct spin-valley locked subbands. The results of our calculations predict a general enhancement in the scattering rate for all subbands, and a jump in the case of spin-down states. This sharp increase associated to the damping of hybrid plasmon modes is almost absent in the uncoupled case. The results suggest an effective way for manipulating collective modes of valley-spin-polarized silicene which may become useful in future valleytronic and spintronic applications. arXiv:1811.12071v1 [cond-mat.mes-hall]

Valley splitting in the van der Waals heterostructure WSe2/CrI3 : The role of atom superposition

“…In addition, the electrostatic potential gradient between WSe 2 and CrI 3 should also play a role in lifting the valley degeneracy. Previous studies demonstrated that applying a vertical external electric field combining with a magnetic field can significantly increase the valley splitting in silicene [8][9][10]12,14 . Similar effects might be at function here in the WSe 2 /CrI 3 , where a vertical electric field is generated from an interlayer electrostatic potential gradient as shown in Fig.…”

“…It is crucial to achieve large valley polarization, in analogous to large spin polarization in spintronics, for the development of valleytronics devices. A plenty of exotic properties such as quantum spin/valley anomalous Hall effect [8][9][10] , valleydependent optoelectronics 11 , spin/valley polarization of plasmons [12][13][14] , magneto-optical conductivity 15 , electrical transport of valley carriers 16 have been explored in the valley-polarized systems. Moreover, valley polarization may interplay with spin polarization, especially to enhance spin polarization 17,18 .…”

Electrically-driven robust tuning of lattice thermal conductivity

“…1. The thickness considering the vdW distance of germanene (4.889 Å) 46 is greater than that of silicene (4.650 Å), 47 which may be due to its larger relative atomic mass and radius. The lattice constants of the three materials increase exponentially with increasing electric field strength in the z direction (perpendicular to the plane).…”

Many-body effects due to the electron–electron interaction in silicene under an applied exchange field: The case of valley–spin coupling

“…50,51 Particularly, we are interested in the valley-spin polarized metal (VSPM) phase of silicene due to its rich underlying valley and spin physics. 24,52 We show that both the real and imaginary parts of silicene self-energy depend upon the spin and valley degrees of freedom where the change in the imaginary part is more pronounced. Moreover, we obtain the single-particle spectral function of carriers for four different states (four distinct combinations of the spin and valley indexes).…”