Speaker
Description
We present the results of a finite-temperature study of a Heisenberg-Dzyaloshinskii-Moriya Hamiltonian on AB-stacked kagome bilayers. We develop an exact analytical coarse-graining procedure to map the microscopic Hamiltonian onto a generalized XY model on a triangular lattice. To leading order, the effective XY model includes both bilinear and biquadratic interactions. In a large portion of the parameter space, the biquadratic couplings dominate in the system, leading to two phase transitions: a high-temperature nematic, and a low-temperature Ising transition. In bilayer systems, these transitions are accompanied respectively by the binding/unbinding of half-integer or integer topological vortex defects. Furthermore, we show that when the ground state is incommensurate, thermal fluctuations change the nature of the low-temperature transition from continuous to first-order. These predictions are confirmed by the numerical Monte-Carlo finite-size analysis.
| Keyword-1 | Kagome |
|---|---|
| Keyword-2 | Nematic |
| Keyword-3 | Phase transitions |
