Scaling and data collapse from local moments in frustrated disordered quantum spin systems

• Main Authors: Kimchi, Itamar (Author), Sheckelton, John P. (Author), McQueen, Tyrel M. (Author), Lee, Patrick A. (Author)
• Other Authors: Massachusetts Institute of Technology. Department of Physics (Contributor)
• Format: Article
• Language: English
• Published: Springer Nature, 2020-04-22T18:01:23Z.
• Subjects: Article
• Online Access: Get fulltext

Recently measurements on various spin-1/2 quantum magnets such as H3LiIr2O6, LiZn2Mo3O8, ZnCu3(OH)6Cl2 and 1T-TaS2-all described by magnetic frustration and quenched disorder but with no other common relation-nevertheless showed apparently universal scaling features at low temperature. In particular the heat capacity C[H, T] in temperature T and magnetic field H exhibits T/H data collapse reminiscent of scaling near a critical point. Here we propose a theory for this scaling collapse based on an emergent random-singlet regime extended to include spin-orbit coupling and antisymmetric Dzyaloshinskii-Moriya (DM) interactions. We derive the scaling C[H, T]/T ~ H−γFq[T/H] with Fq[x] = xq at small x, with q ∈ {0, 1, 2} an integer exponent whose value depends on spatial symmetries. The agreement with experiments indicates that a fraction of spins form random valence bonds and that these are surrounded by a quantum paramagnetic phase. We also discuss distinct scaling for magnetization with a q-dependent subdominant term enforced by Maxwell's relations. ©2018
U.S. Department of Energy, office of Basic Energy Sciences, Division of Materials Sciences and Engineering (grant no. DEFG02-08ER46544)
DOE (grant no. DE-FG02-03-ER46076)