Quasi-equilibrium excitation dependent optical probe spectra of II-VI semiconductor quantum wells at room temperature are investigated within the framework of multi-band semioonductor Bloch equations. The calculations-I include correlation effects beyond the Hdree-Fock level which describe dephasing, interband Coulomb correlations and band-gap renormalbation in second Born approximation. In addition to the carrier-Coulbmb interaction, " the influence of carrier-phonon scattering and inhomogeneous broadening is considered. The explicit calculation of single particle properties like band structure and dipole matrix elements using k p theory makes it possible to c investigate various II-VI material combinations. Numerical results are presented for CdZnSe/ZnSe and CdZnSe/MgZnSSe semiconductor quantum-well systems. ST Keywords: A. semiconductors B. optical properties C. carrier-carrier interaction ' I quantum-well heterostructure, is the absorption coefficient, where n b the refractive index, k (w) = J d t est E(t) is the Fourier transform of the applied probe pulse E (t) and p(w) is the corresponding Fourier transform of the induced polarization density P(t). Note that for a weak probe field the induced polarization p(w) is directly proportional to E (w) so that a(When light propagation in the qu field overlapps with the quantum well(s) and the barrier layers. To account for the resulting This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, e x p m or implied, or s~ssumes any legal liability or rrsponsibiity for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disdased, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

We discuss the transition from a metal to charge or spin insulating phases characterized by the opening of a gap in the charge or spin excitation spectra, respectively. These transitions are addressed within the context of two exactly solvable Hubbard and tJ chains with long range, 1/r hopping. We discuss the specific heat, compressibility, and magnetic susceptibility of these models as a function of temperature, band filling, and interaction strength.We then use conformal field theory techniques to extract ground state correlation functions. Finally, by employing the g-ology analysis we show that the charge insulator transition is accompanied by an infinite discontinuity in the Drude weight of the electrical conductivity. While the magnetic properties of these models reflect the genuine features of strongly correlated electron systems, the charge transport properties, especially near the Mott-Hubbard transition, display a non-generic behavior.(3) which describes spin ( s Kσ ; S z K = ±1/2, C K = 0) and charge ( d K , e K ; S K = 0, C z K = ±1/2) degrees of freedom in an occupation number representation with a hard core constraint,The chemical potential in the presence of an external magnetic field is given by µ σ = µ − σ(gµ B H 0 )/2. In the following we will set µ B ≡ 1, and g = 2. To be precise, we also restrict ourselves to t ≥ 0 and U ≥ −2πt in which case we were allowed to identify K min − ∆ ≡ K max because J K vanishes for K = K min = −∆(L − 1)/2. Note that, formally, the entire spectrum appears to display spin-charge separation at all energies in the sense that the Hamiltonian splits up into independent spin and charge contributions ("strong" spin-charge separation). In reality, however, spin and charge excitations are coupled by the constraint, σ n s K,σ + n d K + n e K = 1; and spin-charge separation only occurs at sufficiently low energies/temperatures, where spin and charge excitations contribute independently to various physical properties.As already discussed above, we will concentrate on the physics of two special limits:(i) the 1/r-Hubbard model in the vicinity of half filling, n < ∼ 1, and (ii) the 1/r-tJ model for n < 1. The latter is obtained by taking the limit U → ∞ of (3) which projects out all double occupancies (h d K → ∞). With the help of the completeness constraint one arrives at the tJ effective Hamiltonian,where, for J = 4t 2 /U ≪ 1, the exchange coupling, J K (U/t), reduces to J K = (J/4) π 2 − (K − ∆/2) 2 . Below, we will adopt the usual standpoint for the tJ model 7 , and treat J as an independent parameter. A. 1/r-Hubbard ModelFrom eq. (3) we can immediately extract the form of eigenstates in an occupation number representation in terms of the effective spin ( s K,σ ) and charge ( e K , d K ) degrees of freedom.

This letter describes a microscopic gain theory for an InGaN/AlGaN quantum well laser. The approach, which is based on the semiconductor Bloch equations, with carrier correlations treated at the level of quantum kinetic theory in the Markovian limit, gives a consistent treatment of plasma and excitonic effects, both of which are important under lasing conditions. Inhomogeneous broadening due to spatial variations in quantum well thickness or composition is taken into account by a statistical average of the homogeneously broadened spectra.

A microscopic analysis of experimental GaInP quantum well gain spectra is presented for a wide range of excitation. A consistent treatment of carrier collision effects, at the level of quantum kinetic theory in the Markovian limit, is found to be necessary for agreement with experiment.

The gain spectrum of a (GaIn)As/(AlGa)As single-quantum-well laser diode is precisely measured at various currents in order to quantitatively check the predictions of a microscopic model. The theory includes carrier—carrier and carrier—LO-phonon collisions which lead to optical dephasing and screening of the Coulomb interaction. The measurements are based on a transmission technique using the broad spectrum of a 10 fs Ti:sapphire laser to obtain sufficient signal to noise ratio over a wide spectral range. We obtain excellent agreement between theoretical and experimental gain spectra and thus can clearly demonstrate the predictive capability of our microscopic model.