2014 We present (a) a local-orbital formulation of the electron-hole interaction in a heteropolar semiconductor which takes into account both the screened electron-hole attraction and its exchange counterpart, giving rise to the excitonic and local-field effects, respectively, and (b) a calculation of the absorption spectrum in GaP, which demonstrates the dominant rôle played by the continuum-e...

The self-interaction error (SIE) plays a central role in density functional theory (DFT) when carried out with approximate exchange-correlation functionals. Its origin, properties, and consequences for the development of standard DFT to a method that can correctly describe multi-reference electron systems by treating dynamic and non-dynamic electron correlation on an equal footing, is discussed...

We consider theoretically the electron–electron interaction induced exchange-correlation effects in the lowest subband of a quasi-one-dimensional GaAs quantum wire structures. We calculate, within the leading order dynamical screening approximation (i.e. the so-called GW approximation of the electron gas theory), the electron self-energy, spectral function, momentum distribution function, inela...

Some of the most promising proposals for scalable solid-state quantum computing, e.g., those using electron spins in quantum dots or donor electron or nuclear spins in Si, rely on a two-qubit quantum gate that is ideally generated by an isotropic exchange interaction. However, an anisotropic perturbation arising from spin-orbit coupling is inevitably present. Previous studies focused on removin...

We experimentally investigate the dynamics of spins in GaAs quantum wells under applied electric bias by photoluminescence (PL) measurements excited with circularly polarized light. The bias-dependent circular polarization of PL (P(PL)) with and without magnetic field is studied. The P(PL) without magnetic field is found to be decayed with an enhancement of increasing the strength of the negati...

We report an electron spin resonance (ESR) study in n-type narrow-gap quantum well (QW) heterostructures. By using the Hartree-Fock approximation based on the 8 k·p Hamiltonian the many-body theory of the ESR in narrow-gap QWs is developed. We have discovered significant enhancement of the ESR g-factor and its low-magnetic-field divergence in both in asymmetric and symmetric QWs which is caused...

Conformational analysis by electron paramagnetic resonance study is naturally limited to free radicals. Very interesting information on these molecules is given by e.p.r., and with short-lived radicals e.p.r. is often the only method for conformational analysis. Then, one needs a complementary hypothesis of theoretical origin. For monoradicals, it can be theoretically and experimentally verifie...

We have measured plasmon energies in Na under high pressure up to 43 GPa using inelastic x-ray scattering (IXS). The momentum-resolved results show clear deviations, growing with increasing pressure, from the predictions for a nearly free-electron metal. Plasmon energy calculations based on first-principles electronic band structures and a quasiclassical plasmon model allow us to identify a pre...

Density functional theory (DFT) is often used to determine the electronic and geometric structures of molecules. While studying alkynyl radicals, we discovered that DFT exchange-correlation (XC) functionals containing less than ∼22% Hartree-Fock (HF) exchange led to qualitatively different structures than those predicted from ab initio HF and post-HF calculations or DFT XCs containing 25% or mo...

This thesis addresses the concept of quantum computing with semiconductor quantum dots. The basic unit of a quantum computer is a quantum mechanical two-level system, the so-called quantum bit (qubit). The qubit can be defined as the spin of an electron confined in a quantum dot or as a two-dimensional subspace of the Hilbert space for several spins. Some semiconductors have several minima in t...