Regensburg 2016 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 50: Correlated Electrons: Frustrated Magnets - Theory

TT 50.2: Talk

Wednesday, March 9, 2016, 15:15–15:30, H18

Classification of gapless Z₂ spin liquids in three-dimensional Kitaev models — •Kevin O’Brien, Maria Hermanns, and Simon Trebst — Institute for Theoretical Physics, University of Cologne, 50937 Cologne, Germany

The formation of spin liquids in frustrated quantum magnets makes for an exciting prospect due to their hosting fractionalized excitations and emergent gauge fields. Unfortunately, they are notoriously difficult to study as there are often no good analytical methods available and Quantum Monte Carlo simulations are hindered by the infamous sign problem. The Kitaev honeycomb model is a notable exception of a frustrated spin model which is exactly solvable and which hosts a number of distinct quantum spin liquid ground states. As such, it allows for a rare opportunity to study the physics of spin liquids with full analytical tractability.

Here we study the fractionalization of magnetic moments into Majorana fermions and a Z₂ gauge field in a generalization of the Kitaev honeycomb model to a number of three-dimensional, tricoordinated lattices. While the excitations of the gauge field are always gapped, the Majorana fermions may form a gapless dispersion with either topologically protected Weyl nodes, symmetry protected nodal lines, or full 2D Fermi surfaces. We show that the nature of these Majorana (semi)metals can be deduced from an elementary analysis of the projective time-reversal and inversion symmetries for a given lattice, allowing us to classify the gapless spin liquids of three-dimensional Kitaev models.