Quantum spin liquid in the 1/3 depleted triangular lattice Ba3(Ru1-xIrx)Ti2O9

Dec. 11. (Fri.), 13:30 PM,  E6-2. 1st fl. #1323
Dr. KwangYong Choi  (Chung-Ang University)

Geometrically frustrated antiferromagnets are a versatile reservoir for emergent quantum-correlated phenomena such as spin liquids, fractionalized excitations, and magnetic monopoles. Recent experiments on the 6H-perovskite family Ba3AB2O9 (A=Cu, Ni, Co, Ru, Ir; B=Sb, Ti) have disclosed a variety of interesting ground states: a random singlet, spin liquid, spin freezing, and 120? ordering, depending on a spin number, spin-orbit coupling, and Jahn-Teller (JT) distortions. In this talk, I will briefly introduce spin liquid in the context of topological order and then present experimental results on the two materials Ba3CuSb2O9 and Ba3Ru1-xIrxTi2O9. In Ba3CuSb2O9, a combined effect of frustration and local JT distortions may create a novel spin-orbital entangled state. Our ESR results provide evidence for intrinsic coupling of spins to orbital degrees of freedom and thereby demonstrate that magnetism is dictated by a spatiotemporal structure of the JT distortions. In Ba3Ru1-xIrxTi2O9, a 1/3 depleted triangular lattice with strong spin-orbit coupling we address the possibility of spin-orbit tuned spin liquids. For the 4d Ru compound, we find experimental signatures of a coexisting spin freezing and dynamically fluctuating state. In the 5d Ir counterpart, spin-orbit coupling melts residual spin freezing while stabilizing a spin liquid state. Our comparative study evidences that spin depletion and spin-orbit coupling conspire to promote a quantum spin liquid in triangular antiferromagnets.

Contact: Heung Sun Sim, Physics Dept., (hs_sim@kaist.ac.kr)