Phase transitions and finite-temperature properties of frustrated magnetic systems

Ehsan Khatami (Georgetown University)

I will present numerical results for the thermodynamic properties of several frustrated magnetic systems, such as the antiferromagnetic Heisenberg model on the checkerboard and kagome lattices utilizing the numerical linked-cluster expansions (NLCE). I will compare NLCE results for the uniform susceptibility, which are exact in the thermodynamic limit, to those obtained experimentally for clinoatacamite and Rb_2Cu_3SnF_12, and discuss the nature of the interactions in these materials. The latter has a pinwheel-distorted kagome lattice and exhibits a valence-bond solid (VBS) ground state. Introducing a zero-temperature NLCE, tailored to capture the correlations of the VBS order, and by tuning a parameter that takes one from the distorted to the uniform Hamiltonian, we study the approach towards the ground state of the uniform kagome lattice Heisenberg model. We find strong evidence for a first-order phase transition before the uniform limit is reached, implying that the ground state of this model is not pinwheel dimerized and is stable to finite dimerizing perturbations.

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