# CMT Seminar: Finite-temperature properties and phase transitions of frustrated magnetic systems

Monday, December 5, 2011 – 3:15pm

Reiss 261A

Ehsan Khatami

Georgetown University

Frustrated magnets often show unusual low-energy behavior and exotic ground state phases, such as the proposed quantum spin liquid. Among the corresponding quantum lattice models, the antiferromagnetic Heisenberg model on the checkerboard lattice has been attracting a lot of theoretical attention for its possible ground state phases in different parameter regions. Here, I will present exact numerical results in the thermodynamic limit for the finite-temperature properties of this model utilizing the numerical linked-cluster expansions (NLCE). I will discuss how the proposed ground state orders are approached as the temperature is reduced. We also study thermodynamic properties of a pinwheel-distorted kagome lattice Heisenberg model with a valence-bond solid (VBS) ground state, realized in Rb_2Cu_3SnF_12 material. 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.

Host: Marcos Rigol