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TT: Fachverband Tiefe Temperaturen

TT 65: Frustrated Magnets: General I

TT 65.11: Vortrag

Donnerstag, 21. März 2024, 12:15–12:30, H 2053

Continuous similarity transformation for critical phenomena: bilayer antiferromagnetic Heisenberg-model and J₁−J₂-model — •Matthias R. Walther¹, Dag-Björn Hering², Götz S. Uhrig², and Kai P. Schmidt¹ — ¹Friedrich-Alexander-Universität Erlangen-Nürnberg, Institut für Theoretische Physik I, Staudtstraße 7, 91058 Erlangen — ²Technische Universität Dortmund, Department of Physics, Condensed Matter Theory, Otto-Hahn-Str. 4, 44227 Dortmund

We apply continuous similarity transformations (CSTs) to the bilayer antiferromagnetic Heisenberg model and the antiferromagnetic J₁−J₂ model on the square lattice. The bilayer Heisenberg model features a well studied, continuous phase transition in the O(3) universality class between a gapless Néel phase and a gapped paramagnetic dimer phase (valence bond solid). The J₁−J₂ features a gapless Néel phase for J₁ ≫ J₂, a gapless columnar phase for J₂ ≫ J₁ and an intermediate phase whose nature is still under debate. We start in both models from the magnetically ordered, collinear phases and approach the quantum phase transitions by the melting of the long-range magnetic order. The CST flow equations are truncated in momentum space by the scaling dimension d so that all contributions with d≤ 2 are taken into account. This amounts up to tracking all linear and quadrilinear terms while neglecting hexatic and higher terms. We locate critical points and estimate critical exponents from the flow of the couplings, the ground-state magnetization and the ground-state energy.

Keywords: QuantumPhaseTransitions; FrustratedMagnets; ContinuousSimilarityTransformation; SpinwaveTheory; AntiferromagneticHeisenbergModel