2021/06/12 by Hofmann, Christoph P.
#FOS: Physical sciences #High Energy Physics - Theory (hep-th) #Strongly Correlated Electrons (cond-mat.str-el)
paper · doi:10.48550/arxiv.2106.06852
Counterintuitive order-disorder phenomena emerging in antiferromagnetically coupled spin systems have been reported in various studies. Here we perform a systematic effective field theory analysis of two-dimensional bipartite quantum Heisenberg antiferromagnets subjected to either mutually aligned -- or mutually orthogonal -- magnetic and staggered fields. Remarkably, in the aligned configuration, the finite-temperature uniform magnetization MT grows as temperature rises. Even more intriguing, in the orthogonal configuration, MT first drops, goes through a minimum, and then increases as temperature rises. Unmasking the effect of the magnetic field, we furthermore demonstrate that the finite-temperature staggered magnetization MHs and entropy density -- both exhibiting non-monotonic temperature dependence -- are correlated. Interestingly, in the orthogonal case, MHs presents a maximum, whereas in mutually aligned magnetic and staggered fields, MHs goes through a minimum. The different behavior can be traced back to the existence of an "easy XY-plane" that is induced by the magnetic field in the orthogonal configuration.