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Regelmäßige Termine
Titel Referent Datum Ort

Schmalian, Schön, Schnirman, Mirlin

Mo 14.00-15.30

10.1

Schön

Di 12.30-14.00

10/1

Do 17.30-19.00

Lehmann HS

Fr 17.15-18.45

Lehmann HS



Geometric phases and spin manipulation in a moving quantum dot

TFP Institutsseminar

Vortragender:

Dr. Tilen Cadez

Datum:

10.12.2013 14:00

Ort:

Raum 10.01, Geb. 30.23 (Physikhochhaus), Campus Süd

Zugehörigkeit:

J. Stefan Institute, Ljubljana, Slovenia

Gastgeber:

Prof. G. Schön

Abstract

I will present a novel approach to manipulate the spin of an electron in a moving quantum dot
(QD) in a one-dimensional (1D) system in the presence of time-dependent spin-orbit interaction
(SOI). First, I will give an exact solution for the wave function of an electron in a semiconductor
quantum wire with constant SOI and driven by external time dependent harmonic confining
potential. The formalism allows analytical expressions for various quantities to be derived, such
as spin and pseudo-spin rotations, energy and occupation probabilities for excited states. It is
demonstrated how spin and pseudo-spin flips can be achieved at high frequencies of order !, the
confining potential level spacing. By an appropriately chosen driving term, spin manipulation can
be exactly performed far into the non-adiabatic regime. Then I will present an exact solution for
the wave-function of an electron in a 1D moving QD in the presence of time-dependent spin-orbit
coupling (SOC). I will focus on the cyclic evolutions of the Hamiltonian and show that after the
evolution the spin rotation is proportional to the area of a closed loop in the parameter space
of the time-dependent quantum dot position and the amplitude of a fictitious classical oscillator
driven by the time-dependent SOC strength. By an appropriate choice of parameters, arbitrary
spin rotations may be performed on the Bloch sphere. The total phase acquired during the cyclic
evolution can be decomposed into dynamical and geometric part. For the system considered I will
give analytical expressions for the geometric phase in both non-adiabatic and adiabatic regime.
The double degeneracy of the Kramers states can be lifted by an external magnetic field and I
will present analytical results for the case of the magnetic field along the direction of the effective
field induced by the moving QD due to the SOI.