Frustrated Magnets

A hot topic in condensed matter physics in recent years is related to the quantum spin liquid (QSL) state, in which strong quantum fluctuations prevent spins from ordering or freezing and they remain in a disordered liquid-like states even at absolute zero. Previous studies have shown that QSL state tends to emerge in the geometrically frustrated systems with two-dimensional low-spin magnetic lattices, in which the interactions among the limited magnetic degrees of freedom is restricted by crystal geometry. When Ising spins are placed on a lattice with triangular motifs (a), AFM interactions cannot be simultaneously satisfied for all positions, therefore leading to the “frustration” of the system. This is called geometric frustration. Unlike QSLs, Kitaev QSL arises from strong anisotropy and bond-dependent interactions that frustrate the spin configuration on a single site of a honeycombb lattice (b). This is called exchange frustration. The Kitaev model, which is an exactly solvable model of honeycombb lattice magnetism, has attracted considerable attention, as it gives rise to quantum and topological spin liquids and emergent Majorana quasiparticles.