Quantum Theory and Applications

Quantum Dynamics of Interacting Electrons

Exact density-functional potentials for time-dependent quasiparticles

In a recent paper [1] we used many-body perturbation theory to determine the exact potential that allows density-functional theory to yield the time-dependent electron density of a propagating electron wavepacket in a semiconducting wire. 

[1] "Exact density-functional potentials for time-dependent quasiparticles", J.D. Ramsden and R.W. Godby, Physical Review Letters 109 036402 (2012).

Quantum Computation and Spintronics

Quantized collective magnetic moment

Sketch of the proposed interpretation of the transverse inter-subband  spin plasmons m±, from ‘Giant Collective Spin-Orbit Field in a Quantum Well: Fine Structure of Spin Plasmons’ Phys. Rev. Lett. 109, 166401 (2012).

This work relates to both fundamental physics and spintronics applications. We show that the macroscopic spin moment of a spin plasmon in a quantum well is quantized and presents a fine structure whose degeneracy is lifted by the existence of a giant collective spin-orbit (SO) field. The effect is remarkable as each individual electron would be expected to precess in its own momentum-dependent SO field, leading to dephasing. Instead, many-body effects lead to a striking organization of the SO fields at the collective level.