17. September 2018
Finite-temperature critical points and quantum critical end point in a 2D magnetThe Mermin–Wagner theorem has long told us that in two dimensions a continuous symmetry can be broken, allowing a finite order parameter, only at zero temperature. Now PSI theorist Bruce Normand, working with colleagues in Aachen, Amsterdam, Lausanne and Paris, has circumvented this rule.
The team was considering the thermodynamics
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The first-order transition in the ground state runs across the entire phase diagram from full frustration to no frustration, and the team showed that a line of finite-temperature critical points should follow it all the way. However, at low frustration the system has an additional line of second-order quantum phase transitions between an ordered magnetic bilayer and the dimer-singlet state. This line terminates on the first-order line, providing a rare example of a `quantum critical end point' (QCEP, meaning the end of a second-order line). The authors used tensor-network calculations to follow the first-order discontinuities in the vicinity of the QCEP, which is a phenomenon yet to be investigated in detail.
ContactDr. Bruce Normand
Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
Phone: +41 56 310 2297, e-mail: email@example.com
Original Publication1. Thermal Critical Points and Quantum Critical End Point in the Frustrated Bilayer Heisenberg Antiferromagnet
Stapmanns J, Corboz P, Mila F, Honecker A, Normand B, Wessel S
Physical Review Letters, 121: 127201, 2018