Report on 2105.05271v3

Abstract

The phase diagrams of highly frustrated quantum spin systems can exhibit firstorder quantum phase transitions and thermal critical points even in the absence of any long-ranged magnetic order.However, all unbiased numerical techniques for investigating frustrated quantum magnets face significant challenges, and for generic quantum Monte Carlo methods the challenge is the sign problem.Here we report on a general quantum Monte Carlo approach with a loop-update scheme that operates in any basis, and we show that, with an appropriate choice of basis, it allows us to study a frustrated model of coupled spin-1/2 trimers: simulations of the trilayer Heisenberg antiferromagnet in the spin-trimer basis are sign-problemfree when the intertrimer couplings are fully frustrated.This model features a first-order quantum phase transition, from which a line of first-order transitions emerges at finite temperatures and terminates in a thermal critical point.The trimer unit cell hosts an internal degree of freedom that can be controlled to induce an extensive entropy jump at the quantum transition, which alters the shape of the first-order line.We explore the consequences for the thermal properties in the vicinity of the critical point, which include profound changes in the lines of maxima defined by the specific heat.Our findings reveal trimer quantum magnets as fundamental systems capturing in full the complex thermal physics of the strongly frustrated regime.

Authors 6

1. Lukas Weber corresponding Aachen Institute for Theoretical Solid State Physics

   Jülich Aachen Research Alliance · RWTH Aachen University

   Affiliation as printed

   Institute for Theoretical Solid State Physics , JARA-FIT , and JARA-HPC , RWTH Aachen University , 52056 Aachen , Germany

   Institute for Theoretical Solid State Physics, JARA-FIT, and JARA-HPC, RWTH Aachen University, 52056 Aachen, Germany

2. A. Honecker

   Centre National de la Recherche Scientifique · CY Cergy Paris Université · Laboratoire de Physique Théorique et Modélisation

   Affiliation as printed

   Laboratoire de Physique Théorique et Modélisation, CNRS UMR 8089, CY Cergy Paris Université, 95302 Cergy-Pontoise, France

3. Bruce Normand

   Paul Scherrer Institute · École Polytechnique Fédérale de Lausanne

   Affiliation as printed

   Institute of Physics , Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne , Switzerland

   Paul Scherrer Institute , CH-5232 Villigen-PSI , Switzerland

   Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland

   Paul Scherrer Institute, CH-5232 Villigen-PSI, Switzerland

4. Philippe Corboz

   Delta Institute for Theoretical Physics · Institute for Theoretical Physics Amsterdam · University of Amsterdam

   Affiliation as printed

   Institute for Theoretical Physics and Delta Institute for Theoretical Physics , University of Amsterdam , Science Park 904 , 1098 XH Amsterdam , The Netherlands

   Institute for Theoretical Physics and Delta Institute for Theoretical Physics, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands

5. Frédéric Mila

   École Polytechnique Fédérale de Lausanne

   Affiliation as printed

   Institute of Physics , Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne , Switzerland

   Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland

6. Stefan Weßel Aachen Institute for Theoretical Solid State Physics

   Jülich Aachen Research Alliance · RWTH Aachen University

   Affiliation as printed

   Institute for Theoretical Solid State Physics , JARA-FIT , and JARA-HPC , RWTH Aachen University , 52056 Aachen , Germany

   Institute for Theoretical Solid State Physics, JARA-FIT, and JARA-HPC, RWTH Aachen University, 52056 Aachen, Germany