Regensburg 2019 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 42: Focus: Many-Body Quantum Chaos

DY 42.8: Talk

Thursday, April 4, 2019, 12:00–12:15, H20

Spin Diffusion Triggered by the Onset of Quantum Chaos in Surrounding Spin Bath — •Walter Hahn and Viatcheslav Dobrovitski — QuTech, Delft University of Technology, The Netherlands

We theoretically investigate spin diffusion driven by a finite quantum spin bath for a realistic solid-state NMR experiment. The total system consists of a disordered spin system which is acted upon by a surrounding spin bath via dipolar coupling. The bath consists of strongly coupled groups which are weakly interacting among each other. By means of numerical simulations, we show that the common expectation that only bath spins contributing to local noise are relevant is violated. In fact, nearby and farther bath spins can be equally important. While nearby bath spins govern the driving noise, the farther bath spins provide ergodicity within the bath by breaking integrability and, thereby, drastically change the spin diffusion dynamics. Specifically, we consider polycrystalline L-alanine in a realistic solid-state NMR setting including all experimental details. Spin diffusion occurs within the disordered carbon-spin subsystem and the spin bath is given by the surrounding proton spins. To modify the properties of the bath, we also consider deuterated alanine with protons replaced by deuterons having a smaller nuclear magnetic dipole moment. For deuterated L-alanine, we show that the driving noise is insufficient to allow for spin diffusion. Instead, spin diffusion is governed by the spin-lattice relaxation of deuteron spins on much larger time scales.