Regensburg 2025 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 41: Quantum-Critical Phenomena (joint session TT/DY)
TT 41.6: Vortrag
Donnerstag, 20. März 2025, 10:45–11:00, H31
Fractionalized multicriticality in Kitaev spin-orbital liquids — •Max Fornoville1,2 and Lukas Janssen3 — 1Max Planck Insti- tute for Solid State Research, 70569 Stuttgart, Germany — 2School of Natural Sciences, Technische Universität München, 85748 Garching, Germany — 3Institut für Theoretische Physik and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany
Two-dimensional spin-orbital magnets with Kitaev-like exchange frustration realize spin-orbital liquid ground states that are characterized by the appearance of gapless Majorana fermions and a static Z2 gauge field. It has been shown that the introduction of an antiferromagnetic Heisenberg interaction between nearest-neighbor spin degrees of freedom facilitates a transition towards a partially ordered spin-orbital liquid state with a spontaneously broken spin-rotation symmetry. The associated quantum critical point belongs to the fractionalized fermionic Gross-Neveu-SO(3)∗ universality class and only partially gaps out the fermionic spectrum. Here, we consider an enlarged theory space, introducing an anisotropic XXZ interaction in the spin sector. The explicit breakdown of spin-rotation symmetry allows for two types of antiferromagnetic order, depending on the nature of the anisotropy. By means of Majorana mean-field theory and ε-expansion to leading order, we uncover the phase diagram of the model and characterize its multicritical behavior. Additionally, we present evidence for the appearance of a symmetry-enhanced first-order transition between the two ordered phases.
Keywords: frustration; spin liquids; fractionalization; Kitaev model; fermionic criticality