Nonlinear bond-operator theory and 1/d expansion for coupled-dimer magnets. I. Paramagnetic phase
Joshi DG, Coester K, Schmidt KP, Vojta M (2015)
Publication Status: Published
Publication Type: Journal article
Publication year: 2015
Journal
Publisher: AMER PHYSICAL SOC
Book Volume: 91
Journal Issue: 9
DOI: 10.1103/PhysRevB.91.094404
Abstract
For coupled-dimer Heisenberg magnets, a paradigm of magnetic quantum phase transitions, we develop a systematic expansion in 1/d, the inverse number of space dimensions. The expansion employs a formulation of the bond-operator technique and is based on the observation that a suitably chosen product-state wave function yields exact zero-temperature expectation values of local observables in the d -> infinity limit, with corrections vanishing as 1/d. We demonstrate the approach for a model of dimers on a hypercubic lattice, which generalizes the square-lattice bilayer Heisenberg model to arbitrary d. In this paper, we use the 1/d expansion to calculate static and dynamic observables at zero temperature in the paramagnetic singlet phase, up to the quantum phase transition, and compare the results with numerical data available for d = 2. Contact is also made with previously proposed refinements of bond-operator theory as well as with a perturbative expansion in the interdimer coupling. In a companion paper, the present 1/d expansion will be extended to the ordered phase, where it is shown to consistently describe the entire phase diagram including the quantum critical point.
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APA:
Joshi, D.G., Coester, K., Schmidt, K.P., & Vojta, M. (2015). Nonlinear bond-operator theory and 1/d expansion for coupled-dimer magnets. I. Paramagnetic phase. Physical Review B, 91(9). https://dx.doi.org/10.1103/PhysRevB.91.094404
MLA:
Joshi, Darshan G., et al. "Nonlinear bond-operator theory and 1/d expansion for coupled-dimer magnets. I. Paramagnetic phase." Physical Review B 91.9 (2015).
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