Dresden 2017 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 76: Poster Session: Transport 2
TT 76.7: Poster
Donnerstag, 23. März 2017, 15:00–19:00, P2-OG1
Dynamics of the pulsed central spin model and the validity of the rotating wave approximation for short pulses — •Lars B. Gravert and Götz S. Uhrig — Lehrstuhl für theoretische Physik I, Technische Universität Dortmund, Germany
We analyze the effect of different pulses and sequences to the central spin model (CSM), especially the influence of the pulse duration and the sequence duration. We compare different setups for the couplings between the central spin and the spin bath as well as for the couplings between bath spins. These setups address experimental systems, e. g. electron spins in quantum dots or 13C in adamantane.
By utilizing the density matrix renormalization group (DMRG) we are able to treat larger spin baths than most other numerical approaches while retaining a full quantum mechanical description. In addition we can choose the couplings between the spin bath and the central spin arbitrarily. We employ an analytic solution for homogeneous couplings, i. e. all bath spins are coupled equally to the central spin. Small spin baths will be approached by standard techniques, e. g. exact diagonalization (ED).
In addition we analyze the validity of the rotating wave approximation (RWA) regarding composite pulses with fast alternating pulse amplitudes. For these pulses additional errors occur within the RWA due to the assumed sharp edges between the different pulse amplitudes. This error is decreased for finite rise times of the pulse amplitudes as well as for high external magnetic fields.