Tuesday, June 8, 2010

Deconfined spinons take the heat

There is a nice paper in Science this week which provides experimental evidence for gapless spin excitations (possibly deconfined spinons) in an organic material that may have a (Mott insulating) spin liquid ground state.
[I thank Andrew Bardin and Ben Powell for bringing it to my attention].

The Figure below shows the temperature dependence of the thermal conductivity kappa(T). The fact that as T->0, kappa/T has a non-zero intercept is a clear signature of gapless excitations. The magnitude of the intercept is comparable to its value in the metallic phase of other organic charge transfer salts, and an order of magnitude larger than what one gets in the d-wave superconducting state due to nodal quasi-particles. [see for example this PRL].
[This is a good example of a Figure because it compares results for several materials so you can see just how clearly different the dmit-131 material is].

The authors also measure the thermal conductance tensor in a magnetic field. Within error the thermal Hall angle was zero. This was motivated by this recent PRL by Katsura, Nagaosa, and Lee, predicted a sizeable thermal Hall effect in quantum spin liquids with deconfined spinons. [Patrick Lee wrote a guest post about this a while back].

1 comment:

  1. Dear Colleagues,

    It should be mentioned that the authors also measure the magnetic field dependence of the thermal conductivity. This very interesting dependence allows us to reveal that the observed quantum spin liquid represents a strongly correlated quantum spin liquid, and relate the field dependence to the relaxation properties of the quantum spin liquid in herbertsmithite.
    Please see: EPL, 103, 67006 (2013);
    doi: 10.1209/0295-5075/103/67006

    With warm regards,
    Vasily Shaginyan