We present a study of the interaction mechanisms in magnetic trilayer structures with an MgO barrier grown by molecular beam epitaxy. The interlayer exchange coupling, Aex, is determined using SQUID magnetometry and ferromagnetic resonance (FMR), displaying an unexpected oscillatory behaviour as the thickness, tMgO, is increased from 1 to 4 nm. Transmission electron microscopy confirms the cont...

This thesis describes the calculation of exchange interactions for systems of electrons, and their potential uses for quantum information processing. The first part treats exchange between donor impurities (including especially deep donors) in silicon, while the second describes exchange in copper and manganese phthalocyanines. Part I uses the quantum defect method and a model central-cell corr...

For the traditional low Tc superconductors, the superconducting condensation energy is proportional to the change in energy of the ionic lattice between the normal and superconducting state, providing a clear link between pairing and the electron–ion interaction. Here, for the t-J model, we discuss an analogous relationship between the superconducting condensation energy and the change in the e...

We have used the Hartree-Fock Random Phase Approximation (HFRPA) to study the interacting electron gas in a quantum wire. The spectra of intersubband spin-flip excitations reveal a considerable red shift with respect to single-particle HF energies. That signals on appearance of collective intersubband spind-density excitations due to the exchange interaction. The long wavelength dispersions of ...

Using a many-body approach based on atomistic pseudopotential wave functions we show that the electronhole exchange interaction in semiconductor quantum dots is characterized by a large, previously neglected long-range component, originating from monopolar interactions of the transition density between different unit cells. The calculated electron-hole exchange splitting of CdSe and InP nanocry...

We use the exact strong-interaction limit of the Hohenberg-Kohn energy density functional to approximate the exchange-correlation energy of the restricted Kohn-Sham scheme. Our approximation corresponds to a highly nonlocal density functional whose functional derivative can be easily constructed, thus transforming exactly, in a physically transparent way, an important part of the electron-elect...