Regensburg 2022 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 14: Cooperative Phenomena: Spin Structures and Magnetic Phase Transitions
MA 14.2: Vortrag
Dienstag, 6. September 2022, 10:00–10:15, H47
Poisson-Dirichlet distributions and weakly first-order spin-nematic phase transitions — •Nils Caci1, Peter Mühlbacher2, Daniel Ueltschi2, and Stefan Wessel1 — 1RWTH Aachen University, Aachen, Germany — 2University of Warwick, Coventry, United Kingdom
Weakly first-order transitions, i.e. discontinuous phase transitions with very large correlation lengths, have become a vivid subject in condensed matter research and beyond in recent years. Therefore, establishing quantum systems in which weakly first order phase transitions can be robustly demonstrated is of great interest. We present a quantitative characterization of generic weakly first-order thermal phase transitions out of planar spin-nematic states in three-dimensional spin-one quantum magnets, based on calculations using Poisson-Dirichlet distributions (PD) within a universal loop model formulation, combined with large-scale quantum Monte Carlo calculations. In contrast to earlier claims, the thermal melting of the nematic state is not continuous, instead we identify a weakly first-order transition. Furthermore, we obtain exact results for the order parameter distribution and cumulant ratios at the melting transition. Our findings establish the thermal melting of planar spin-nematic states as a generic platform for quantitative approaches to weakly first-order phase transitions in quantum systems with a continuous SU(2) internal symmetry.