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Phase transitions in condensed matter are often linked to exotic emergent properties. In this talk, I will show that applying a magnetic field in a fully frustrated bilayer Heisenberg antiferromagnet creates a novel emergent criticality. The quantum phase diagram contains four states, the DS (singlets on every interlayer dimer bond), DTAF (all triplets with antiferromagnetic order), TC (a singlet-triplet checkerboard) and FM (saturated ferromagnet). The thermal phase diagram is dominated by a wall of discontinuities extending from the zero-field DTAF-DS transition to a quantum critical endpoint where the field drives the DTAF and TC into the FM. This first-order wall is terminated at finite temperatures by a line of critical points, where the Berezinskii-Kosterlitz-Thouless (BKT) transition of the DTAF and the thermal Ising transition of the TC also terminate. We demonstrate by quantum Monte Carlo simulations that the BKT transition does not change the Ising nature of the DTAF-DS critical line. By contrast, the combination of symmetries merging on the multicritical DTAF-TC line leads to a 4-state Potts universality not contained in the microscopic Hamiltonian, which we associate with the Ashkin-Teller model. Our results represent a systematic step in understanding emergent phenomena in quantum magnetic materials including the “Shastry-Sutherland compound” SrCu2(BO3)2.
Reference:
[1] Yuchen Fan, Ning Xi, Changle Liu, Bruce Normand, and Rong Yu, arXiv:2306.16288
Dr. Rong Yu is a professor of physics at Renmin University of China. He received his Ph.D. degree from University of Southern California in 2007. He worked at University of Tennessee, Knoxville and Rice University as a postdoctoral research associate before he joined the faculty at Renmin University. He has been working on theory of correlated electronic systems. Current research interests include frustration and disorder effects in quantum magnets, superconductivity and correlation effects in unconventional superconductors.
Tencent Meeting link: https://meeting.tencent.com/dm/MjzIBiF7MVys Meeting ID: 988 734 855