Effects of intervalence band coherences on the coherently coupled heavy-hole–light-hole Stark shift in semiconductor quantum wells (original) (raw)
Related papers
Physical Review Letters, 2001
We report the experimental observation of coherently coupled heavy-hole-light-hole Stark shifts, i.e., light-hole exciton shifts under heavy-hole exciton pumping conditions, in InGaAs quantum wells. The theoretical analysis of the data is based on a full many-body approach (dynamics-controlled truncation formalism) in the third-order nonlinear optical regime. It is shown that the Stark shift data can be interpreted as strong evidence of suitably defined nonradiative intervalence band coherences in a semiconductor quantum well. Hence, the observations establish a semiconductor analog of Raman coherences in three-level atoms.
Superlattices and Microstructures, 2001
The paper deals with the detailed theoretical investigation of optical coherent transient processes in a narrow direct gap semiconductor quantum well structure (QWS), duly irradiated by a near band gap resonant ultrashort pulsed laser with moderate excitation intensity. The photoinduced band-to-band electronic transitions are considered from both the heavy-hole (hh) and light-hole (lh) valence bands to the lowest (1s) exciton state below the fundamental absorption edge. Since the hole populations in both hh and lh bands are nontrivial in the case of the transverse plane in a QWS, we have recognized that the hh and lh excitons participate in photoinduced transitions. The photoinduced electron density is chosen to be less than the Mott density such that various many-body processes, otherwise significant, can be neglected. The well-established time-dependent perturbation treatment of the semiconductor Bloch equations has been followed to calculate the induced polarization as well as the differential transmission spectra. We find from the numerical estimates made for a GaAs/AlGaAs single QWS shined by a femtosecond pulsed Ti : Sapphire laser that the transmission characteristics of the coherent transient processes are dominated by the lh species in the QWS. Rabi oscillation and Stark splitting as calculated for the two-hole species QWS agree qualitatively very well with recent experimental observations.
Quantum Coherence of Continuum States in the Valence Band of GaAs Quantum Wells
Physical Review Letters, 1996
Quantum beats of heavy and light holes in GaAs quantum wells are investigated in femtosecond time-resolved four-wave mixing and transmission experiments as a function of optical excitation energy. Under nonexcitonic excitation conditions, the four-wave mixing signal disappears due to the immediate loss of the interband coherence of continuum states. In the transmission experiment, the quantum beats are observed up to excess energies of 75 meV above the exciton resonances. The experimental data clearly demonstrate the coherence of continuum states in the valence band. Changes of the beat frequency with the excitation energy are due to the dispersion of the valence bands.
Stark shift effects in rectangular and graded gap quantum wells
Surface Science, 1999
We study the Stark effect in rectangular quantum wells and in quantum wells with linear variation of the composition. The energies of the bound electronic states, the transition energies and their Stark shifts are calculated when a longitudinal electric field is applied. The spatial overlap of the electron and hole states and the intensity of the main optical transitions are considered, and their dependence on the electric field strength is discussed. We compare the Stark effect characteristics of the rectangular and graded composition quantum wells. Numerical calculations are performed within the framework of a semi-empirical sp3s1 tight-binding model, the virtual crystal approximation and the surface Green function matching method. A comparison between the theoretical results and the experimental data available for these systems is made, and a critical discussion is presented.
Wave-packet analysis of the quantum-confined Stark effect in coupled double quantum wells
Physical Review B, 1991
The excitonic spectra and certain features of the quantum dynamics of electron-hole pairs in coupled double quantum wells under electrical bias are analyzed by a wave-packet propagation method. The excitonic system is described by a two-band model in the effective-mass envelope-wave-function approximation. The results describe the behavior of the bare pair distribution of electrons and holes under the Coulomb interaction and a longitudinal electric field (applied perpendicular to the wells). Many-body interaction, space-charge effects, and scattering by lattice and impurity mechanisms are not taken into
Stark effect near the type-I–type-II transition point in semiconductor quantum wells
Physical Review B, 1994
We show the effect of an electric field normal to the quantum-well (QW) plane on the shape of a hole wave function in the vicinity of the type-Itype-II transition point, which leads to (i) the strong decrease of the oscillator strength of elb 1, elb 3 exciton states, and (ii) an increase in the strength of the e lh2 transition, which is forbidden in the absence of the field. The variational calculation of the hole wave function in a type-II QW reveals the existence of some critical electric field which initiates a shift of the hole center of mass to one of the interfaces.
Stark effect in diffused quantum wells
Superlattices and Microstructures, 1999
We study the longitudinal Stark effect in diffused AlGaAs/GaAs quantum wells grown along the [1,0,0] direction. The energies of the ground electron and hole states and the first excited hole state are calculated for different diffusion lengths and electric field strengths. The energies of the main optical transitions and their Stark shifts are found. The intensities of the transitions are considered in terms of the bound states spatial distributions. The calculations are carried out within the semi-empirical sp 3 s * tight-binding model including spin and the surface Green function matching method. We compare our results with those obtained by means of other theoretical methods.