Description:

Title: Chiral quantum states stabilized by anisotropic scattering in 3He and UPt3

Speaker: Professor W. P. Halperin, Northwestern University

Abstract: New chiral states of 3He have recently been studied at Northwestern and are similarly thought to exist in a number of superconducting compounds, like UPt3 and Sr2RuO4. In the past few years or more, the condensed matter physics community has become interested in these superconductors and superfluids, driven in part from predictions for potential applications of topologically non-trivial quantum states. I will focus on measurements of physical properties which are a consequence of chiral symmetry, most clearly in evidence in UPt3 and superfluid 3He. These systems have multiple thermodynamic phases, each with a different order parameter structure. The theoretical prediction that anisotropic quasiparticle scattering favors the stability of anisotropic quantum states, in particular the chiral states of superfluid 3He is confirmed in our experiments. This general result might also be the case in UPt3 and possibly other anisotropic unconventional superconductors suggested by recent specific heat experiments. I will discuss the origin of the symmetry breaking field in UPt3, and follow with a suggestion that antiferromagnet ism might be attributed to an inhomogeneous impurity phase associated with prism plane stacking faults which we have observed in this material. In the absence of these defects the chiral phase of UPt3 might be the uniquely stable thermodynamic phase.

Keywords: Physics, Astronomy, CMP