Dresden 2026 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 31: Frustrated Magnets I (joint session MA/TT)
TT 31.11: Talk
Tuesday, March 10, 2026, 12:15–12:30, POT/0361
Fate of the Triangular Dirac spin liquid under an external magnetic field — •Sasank Budaraju1,2, Josef Willsher3, Federico Becca4, Johannes Knolle1,2, and Frank Pollmann1,2 — 1Technical University of Munich, TUM School of Natural Sciences, Physics Department, 85748 Garching, Germany — 2Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, 80799 München, Germany — 3Max-Planck-Institut fur Physik komplexer Systeme, 01187 Dresden, Germany — 4Dipartimento di Fisica, Universita di Trieste, Strada Costiera 11, I-34151 Trieste, Italy
We investigate the J1-J2 Heisenberg model under an external Zeeman field using the Variational Monte Carlo approach. Simple variational ansatzes are proposed for several candidate ordered states, and their energetics are compared on large clusters to obtain the phase diagram for small/moderate fields. For small J2, we capture a continuous transition from the Y to the "Up-Up-Down" (UUD) states as predicted by spin-wave theory. Additionally, around the highly frustrated region, we demonstrate that the ground state in the presence of a small field is a condensate of monopoles, which are gapless gauge excitations of the U (1) spin liquid. The monopole condensate is shown to be the ground state for a significant region of phase diagram, which we estimate using finite size numerics. Our results imply that the Dirac spin liquid is unstable to a condensation of monopoles in the presence of external fields.
Keywords: Quantum Spin liquid; Dirac Spin liquid; Triangular lattice antiferromagnets; Magnetization plateaus; Quantum Monte Carlo