All-optical injection and control of spin and electrical currents in quantum wells

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

“…Following previous theories, 11,13,17,19,21 we have used a framework based on (i) a separation of the initial carrier photoinjection and the subsequent carrier scattering, and (ii) a perturbative expansion in the optical field amplitudes, with injection rates obtained in a Fermi's golden rule limit for the bichromatic field. The injection rates for carrier population control, spin control, current injection, and spin current injection, have been described phenomenologically by tensors ξ (I) , ζ (I) , η (I) , and µ (I) , respectively.…”

“…17 The phases of the material response tensors η (I) , ξ (I) , µ (I) , and ζ (I) are related to the phases of the one-and two-photon matrix elements, D (1) n and D…”

“…The twophoton transition amplitude is more difficult to deal with due to the sum over intermediate states; however, in our set of approximations it has been done exactly. 38,39,40 In order to proceed analytically, it is common to use (17) and (18), and then make an expansion in k of the velocity matrix elements v nm (k) about the Γ point. 30,36,37,38,39,40 However, due to the degeneracy at the Γ point, the coefficients of such an expansion can depend on the direction of k. 81 To proceed, we note that Wannier excitons have large spatial extent and hence only a small region of wavevectors is important for them, i.e., A κ cv (k) is peaked in the region of k near κ.…”

“…10 Interband '1 + 2' interference in unbiased semiconductors, which is our interest here, allows independent control of electrical current injection 11,12 and spin current injection. 13,14,15,16,17,18 Furthermore, in noncentrosymmetric semiconductors, it allows independent control of carrier populations (i.e., absorption) 19,20 and carrier spin polarization. 21, 22 In each scenario, the experimenter can control the interference by adjusting the phases of the two colors.…”

An Approach To “Quantumness” In Coherent Control

“…For example, the path alternatives are given by the two excitation processes in a 1 vs. N coherent control scenario. The resultant CCI framework is general and applicable to many systems, from atoms [15,66] to molecules [27,45,[67][68][69] to bulk solids [4,5,20,30,[70][71][72][73][74][75]. Further, the control field can be in a semiclassical coherent or in a quantum state of light, such as a multimode Fock state or a squeezed state.…”