Order-by-disorder in the XY highly frustrated honeycomb lattice under an external magnetic field

F. A. GÓMEZ ALBARRACÍN; H. D. ROSALES

Trieste

Conferencia; Conference on Frontiers in Two-Dimensional Quantum Systems; 2017

In the last year, the honeycomb iridates have been greatly studied since they are candidates to showing Kitaev interactions. Experimental results show that other additional interactions are at play, and for example Heisenberg and further neighbour Kitaev interactions have been suggested and studied [1]. Recently, the classical case of the highly frustrated honeycomb lattice was presented in connection to these models [2]. For Heisenber spins, this model shows a remarkable feature: it is a classical spin liquid with ?pinch points? in the structure factor but with a non-bipartite dual lattice. For XY spins, order by disorder is at play, also showing particular features in the structure factor. In this work, we study the classical honeycomb lattice at the maximally frustrated pointJ1/2 = J2 = J3 for XY spins under an external magnetic field. At low enough temperatures thermal fluctuations select a sub-manifold of states. In particular, there are two collinear pseudoplateaux at M=1/3 and M=2/3. The low temperature states are characterized through several and different order parameters, since the system is organized in plaquettes that retain some degeneracy. For higher values of the magnetic field the order parameters show a Z6 distribution.[1] S. M. Winter, A. A. Tsirlin, M. Daghofer, J. van den Brink, Y. Singh, P. Gegenwart, R. Valenti, preprint arxiv/1706.06113 (2017).[2] J. Rehn, A. Sen, K. Damle and R. Moessner, Phys. Rev. Letters 117, 16 (2016).