Magnetization process in frustrated honeycomb lattices: a classical approach

F. A. GÓMEZ ALBARRACÍN

Toulouse

Seminario; Seminario del Grupo de Electrones Fuertemente Correlacionados (GEFC) en el Laboratoire de Physique Theorique, Toulouse, Francia; 2017

GEFC - LPT

(talk) In this talk we first introduce the notion of highly frustrated points in several lattices, and discuss the different phenomena found in each case. We then focus on the highly frustrated point of the honeycomb lattice, J1/2=J2=J3, which can be described by six spin plaquettes and has been shown as a possible spin liquid phase (Cabra, Lamas, Rosales PRB 2011) and has recently been studied in the classical case (Rehn Moessner PRL 2016), since up to third nearest neighbour couplings have been considered relevant for the honeycomb iridates. We here discuss our recent work on the effect of a magnetic spin at low temperatures for XY spins in this point, showing that thermal order by disorder selects different phases. Most notably two collinear plateaux (UUUUDD at m=1/3 and UUUUUD at m=2/3) and phases that can be described by a Z6 parameter per plaquette. This phases have soft modes that can be found by exchanging pairs of spins in loops of plaquettes. We then procede to discuss recent papers on semiclassical approaches to iridate materials, regarding the competition between exchange and Kitaev couplings at different distances. We also show preliminary results on our work on the competition between first and second nearest neighbour Kitaev couplings under a magnetic field.