Emergent Quantum Dynamics In A Spin Liquid

Dr. Arnab Banerjee (host Henriksen/Ogilvie), Oak Ridge National Laboratory
November 8, 2017 at 4:00 pm
204 Crow
Event Description 

At low temperature the spins in a material tend to freeze into regular patterns, like a ferromagnet or an antiferromagnet. However, in some materials, in the presence of competing interactions and large quantum fluctuations, the spins do not freeze, even to very low temperatures. Such a state is called a quantum spin liquid (QSL). Since Anderson proposed in 1970, QSLs have captured the fascination of physicists because its highly degenerate ground state hosts queer emergent topological excitations with fractional quantum numbers, called fractionalized excitations. In 2006, Alexei Kitaev proposed the existence of a peculiar QSL on a honeycomb lattice with fractionalized excitations resembling Majorana Fermions and states obeying non-abelian statistics - exciting prospects for both basic physics and applications towards a lossless technology for quantum qubits. In this talk, I will describe our recent range of experiments in a the magnetic Mott insulator a-RuCl3. In this compound, a strong spin-orbit coupling and an octahedral crystal field provides a favorable condition for investigating the Kitaev’s QSL. Prominently, our neutron scattering measurements reveal a continuum of fractionalized excitations despite a long-range ordered ground state confirming that the material is proximate to a QSL. In a magnetic field the long-range order vanishes the continuum becomes gapped, giving rise to hopes of a state where a direct evidence of non-abelian excitations can perhaps be measured.

Coffee: 3:30 pm, 245 Compton