Frank Pollmann |
Monday, 16:10 - 16:40 | |

Dynamical signatures of quantum spin liquids | ||

Condensed matter is found in a variety of phases, the vast majority of which are characterized in terms of symmetry breaking. However, the last few decades have yielded a plethora of theoretically proposed quantum phases of matter which fall outside this paradigm. Recent focus lies on the search for concrete realizations of quantum spin liquids. These are notoriously difficult to identify experimentally because of the lack of local order parameters. In my talk, I will discuss universal properties found in dynamical response functions that are useful to characterize these exotic states of matter. First, we show that the anyonic statistics of fractionalized excitations display characteristic signatures in threshold spectroscopic measurements. The low energy onset of associated correlation functions near the threshold show universal behavior depending on the statistics of the anyons. This explains some recent theoretical results in spin systems and also provides a route towards detecting statistics in experiments such as neutron scattering and tunneling spectroscopy [1]. Second, we introduce a matrix-product state based method to efficiently obtain dynamical response functions for two-dimensional microscopic Hamiltonians, which we apply to different phases of the Kitaev-Heisenberg model. We find significant broad high energy features beyond spin-wave theory even in the ordered phases proximate to spin liquids. This includes the phase with zig-zag order of the type observed in a-RuCl3, where we find high energy features like those seen in inelastic neutron scattering experiments. [1] S. C. Morampudi, A. M. Turner, F. Pollmann, and F. Wilczek, arXiv:1608.05700. [2] M. Gohlke, R. Verresen, R. Moessner, and and F. Pollmann, arXiv:1701.04678. |