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TT: Fachverband Tiefe Temperaturen

TT 81: Nonequilibrium Quantum Many-Body Systems III

TT 81.3: Vortrag

Donnerstag, 15. März 2018, 10:00–10:15, H 3010

Non-Markovian Decay of Nuclear Spins Coupled to Itinerant Electrons — •Stephanie Matern and Bernd Brauncker — SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, United Kingdom

We study the full time evolution of a nuclear spin coupled to itinerant electrons through the hyperfine interaction, with a particular focus on memory effects leading to a non-Markovian behaviour. We show that even a noninteracting electron system causes a notable memory effect due to the restriction of fluctuations by the Fermi surface. The resulting short time dynamics of the nuclear spin is dominated by a logarithmic, temperature independent decay before crossing over to the standard, thermally induced exponential decay. But even at the longer time scales the initial non-Markovian decay causes a systematic reduction of the decay amplitude that should be detectable. Our approach is based on an expansion of the exact Nakashima-Zwanzig equation in the hyperfine coupling constant, set up to preserve the analytical structure of the memory kernel that causes the non-Markovian behaviour. Our results are analytical and describe the full time range from the novel non-Markovian contributions to the well-known exponential decay expressions.