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Dresden 2017 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 72: Correlated Electrons: Frustrated Magnets - General 2

TT 72.4: Talk

Thursday, March 23, 2017, 15:45–16:00, HSZ 204

J1-J2 Heisenberg model on a triangular-lattice bilayer — •Darshan G. Joshi1 and Matthias Vojta21Max Planck Institute for Solid State Research, D-70569 Stuttgart, Germany — 2Institut für Theoretische Physik, Technische Universität Dresden, 01062 Dresden, Germany

We consider a triangular-lattice bilayer Heisenberg model for spins 1/2 with antiferromagnetic nearest-neighbor and next-nearest-neighbor interactions. We determine the phase diagram and the dispersion of elementary excitations using variants of bond-operator theory. Large inter-layer coupling yields a dimer quantum paramagnet, while magnetic order is possible for weak inter-layer coupling. Frustration can induce flat portions of triplon bands in the dimer phase, opening the window to find exotic states in the vicinity to the transition point to ordered phases. For weak inter-layer coupling we reproduce the possible spin-liquid state known from the single-layer J1-J2 model which occurs when 120 order is destroyed by increasing J2. Remarkably, this state is destabilized in favor of magnetic order with increasing inter-layer coupling before amplitude fluctuations destroy magnetic order at large inter-layer coupling.

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