Theoretical Physics Seminar: James de Lisle (Osaka University)

Identifying Weyl Superconductivity in UCoGe via the Chiral-Magnetothermal effect

Abstract: The experimental identification of Weyl superconductivity (WSC) presents a more difficult problem than its Weyl semimetal cousin. The standard surface measurements such as ARPES are no longer useful as the relevant systems are at very low temperatures and therefore lie outside the sensitivity range. We show that one can identify WSC in UCoGe [1, 2] due to a new phenomenon we call the chiral- magnetothermal effect (CMTE). CMTE is analogous to the chiral anomaly in other condensed matter systems. In the CMTE the electric and magnetic field are replaced by a temperature gradient and an effective magnetic field that arises from a torsional field (such as that from the vortex texture of the superconducting order parameter). The effect, if present, should give rise to spin polarisation, an effect which cannot be attributed to Zeeman splitting due to the absence of a magnetic field in the bulk. Using non-equilibrium quantum field theory in the quasiclassical limit, we show that the spin polarisation that occurs due to this effect appears under the first order quantum correction to the quasiclassical propagator. Such an effect should be observable using standard Knight shift measurements. 
[1] Mineev V P Phys. Rev. B 66 134504 (2002)
[2] Hattori T et al. Phys. Rev. Lett. 108 066403 (2012)