Berlin 2024 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 65: Frustrated Magnets: General I

TT 65.13: Vortrag

Donnerstag, 21. März 2024, 12:45–13:00, H 2053

Extracting quantum-critical properties from directly evaluated enhanced perturbative continuous unitary transformations — •Lukas Schamriß¹, Matthias R. Walther¹, Dag-Björn Hering², and Kai P. Schmidt¹ — ¹Department Physik, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Staudtstr. 7, 91058 Erlangen, Germany — ²Condensed Matter Theory, TU Dortmund University, Otto-Hahn Str. 4, 44221 Dortmund, Germany

Ising models in a transverse field are paradigmatic models for quantum phase transitions of various universality classes depending on the lattice geometry and the choice of antiferromagnetic or ferromagnetic coupling. We investigate the quantum phase diagram of the bilayer antiferromagnetic transverse-field Ising model on the triangular lattice with an Ising-type interlayer coupling. Without a field, the model hosts a classically disordered ground state, and in the limit of decoupled layers it exhibits a 3dXY 'order by disorder' transition. Our starting point for the unknown parts of the phase diagram is a high-order perturbative calculation from the limit of isolated dimers. Directly evaluated enhanced perturbative continuous unitary transformations (deepCUTs) are used to calculate non-perturbatively extrapolated numerical data for the ground-state energy and the energy gap which coincide with the perturbative series up to the order with respect to which the deepCUT is truncated. We develop a general scheme to extract quantum critical properties from the deepCUT data based on critical scaling and a strict correspondence between the truncation used for deepCUT and the length scale of correlations at the critical point.

Keywords: Frustration; criticality; Ising; Bilayer; scaling