Fractionalization in an easy-axis Kagome antiferromagnet

Abstract

We study an antiferromagnetic spin-1/2 model with up to third\nnearest-neighbor couplings on the Kagome lattice in the easy-axis limit, and\nshow that its low-energy dynamics are governed by a four site XY ring exchange\nHamiltonian. Simple ``vortex pairing'' arguments suggest that the model\nsustains a novel fractionalized phase, which we confirm by exactly solving a\nmodification of the Hamiltonian including a further four-site interaction. In\nthis limit, the system is a featureless ``spin liquid'', with gaps to all\nexcitations, in particular: deconfined S^z=1/2 bosonic ``spinons'' and Ising\nvortices or ``visons''. We use an Ising duality transformation to express vison\ncorrelators as non-local strings in terms of the spin operators, and calculate\nthe string correlators using the ground state wavefunction of the modified\nHamiltonian. Remarkably, this wavefunction is exactly given by a kind of\nGutzwiller projection of an XY ferromagnet. Finally, we show that the\ndeconfined spin liquid state persists over a finite range as the additional\nfour-spin interaction is reduced, and study the effect of this reduction on the\ndynamics of spinons and visons.\n

Keywords

Affiliated Institutions

• University of California, Santa Barbara US
• Yale University US

Related Publications