Berlin 2015 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 30: Correlated Electrons: Spin Systems and Itinerant Magnets – Frustrated Magnets 3 (jointly with MA)

TT 30.5: Talk

Tuesday, March 17, 2015, 10:30–10:45, H 0110

Non-linear bond operator theory and 1/d expansion for coupled dimer magnets — •Darshan G. Joshi and Matthias Vojta — Institut für Theoretische Physik, Technische Universität Dresden, 01062 Dresden, Germany

For coupled-dimer Heisenberg magnets, a paradigm of magnetic quantum phase transition, we develop a systematic expansion in 1/d, where d is spatial dimension, using bond operators. We apply this technique to a model of dimers on a hyper-cubic lattice, a generalization of the square-lattice bilayer Heisenberg model to arbitrary d. We calculate physical observables at zero temperature in both the quantum paramagnetic and anti-ferromagnetic phases and show that the 1/d expansion consistently describes the entire phase diagram including the quantum critical point. In particular, we determine the dispersion and spectral-weight distribution of the elementary excitations, including the Higgs mode of the anti-ferromagnetic phase.