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Wednesday, October 20 2021
2:00pm - 3:00pm
Howey N201 -N202 In-person / simultaneously at
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Quantifying entanglement and detecting Kardar-Parisi-Zhang transport in spin chains using neutron scattering

School of Physics ,Quantum Matter Seminar| Dr.  Allen Scheie| Neutron Scattering Division, ORNL  

Quantum entanglement is a key driver of exotic physics in quantum materials, but it historically has been extremely hard to measure. In the first part of this talk I will discuss recent experiments showing how quantum spin entanglement can be extracted from neutron data using the tools of quantum information theory. We applied these protocols to 1D spin chains KCuF3, Cs2CoCl4, and triangular lattice KYbSe2. Of the protocols three we tested, we found Quantum Fisher Information (QFI) to be the most experimentally robust. Crucially, these protocols do not require theoretical models, which are only sometimes available for 2D and 3D quantum systems. In the second part of the talk, I discuss a separate set of experiments on the Heisenberg spin chain KCuF3 showing Kardar-Parisi-Zhang (KPZ) hydrodynamics at room temperature. By comparing with theoretical simulations, we show that the high temperature dynamic exponent of KCuF3 is inconsistent with ballistic or diffusive transport, indicating instead superdiffusive KPZ behavior. This verifies a recent theoretical prediction, and shows the influence of quantum effects even at room temperature.

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