Excitonic effects on the two-color coherent control of interband transitions in bulk semiconductors

Abstract

Quantum interference between one-and two-photon absorption pathways allows coherent control of interband transitions in unbiased bulk semiconductors; carrier population, carrier spin polarization, photocurrent injection, and spin current injection may all be controlled. We extend the theory of these processes to include the electron-hole interaction. Our focus is on photon energies that excite carriers above the band edge, but close enough to it so that transition amplitudes based on low order expansions in k are applicable; both allowed-allowed and allowed-forbidden two-photon transition amplitudes are included. Analytic solutions are obtained using the effective mass theory of Wannier excitons; degenerate bands are accounted for, but envelope-hole coupling is neglected. We find a Coulomb enhancement of two-color coherent control process, and relate it to the Coulomb enhancements of one-and two-photon absorption. In addition, we find a frequency dependent phase shift in the dependence of photocurrent and spin current on the optical phases.The phase shift decreases monotonically from π/2 at the band edge to 0 over an energy range governed by the exciton binding energy. It is the difference between the partial wave phase shifts of the electron-hole envelope function reached by one-and two-photon pathways.

All-optical injection of charge, spin, and valley currents in monolayer transition-metal dichalcogenides

“…For semiconductors, this shift is too small 28 . However, since calculations for exciton binding energies 29 indicate that monolayer TMDs have a stronger electron-hole interaction, it is reasonable to expect a considerable shift δ for them.…”

“…It has been applied in several experimental scenarios involving bulk and nanostructure semiconductors [14][15][16][17][18][19]28 , it has been predicted and seen in graphene [20][21][22] , and experiments to lead to its observation in topological insulators have recently been proposed 23 . Here we study how it can be used for the injec- The explicit expression for the injection rate coefficients are shown in the Appendix A.…”

Microscopic analysis of charge and spin photocurrents injected by circularly polarized one-color laser pulses in GaAs quantum wells

“…The two-color current generation process uses the interference of one-and two-photon excitations, and is a third-order nonlinear optical process that does not rely on the material symmetry or details of the band structure. [2][3][4]7,[12][13][14][15][16][17]20,25,26,[28][29][30] One-color injection currents however arise from a spin splitting of the energy bands in systems of reduced symmetry and are of second order in the light field, i.e., the currents are proportional to the light intensity. Since this current is maximal for circularly polarized excitation, it is referred to as circular photogalvanic effect.…”

“…The multisubband SBE include Coulomb many-body effects in time-dependent Hartree-Fock approximation and are thus capable of describing excitonic effects which are known to influence one-and two-color injection currents. 15,16,24,30 Since the injection charge currents generated by circularly polarized one-color excitation are spin polarized, 9,27 they are accompanied by spin currents. These spin currents are also described by our multisubband SBE and analyzed below.…”

Optical spin- and current-injection study on Si(111)-In surfaces

“…The optical injection of current is a second-order optical nonlinear effect and has been the subject of research in recent years [21][22][23][24][25][26]. In noncentrosymmetric crystals, an observable photocurrent can be injected with a single optical beam [26][27][28].…”