Abstract
Spanning a broad range of physical systems, complex symmetry breaking is widely recognized as a hallmark of competing interactions. This is exemplified in superfluid 3He which has multiple thermodynamic phases with spin and orbital quantum numbers S = 1 and L = 1, that emerge on cooling from a nearly ferromagnetic Fermi liquid. The heavy fermion compound UPt3 exhibits similar behavior clearly manifest in its multiple superconducting phases. However, consensus as to its order parameter symmetry has remained elusive. Our small angle neutron scattering measurements indicate a linear temperature dependence of the London penetration depth characteristic of nodal structure of the order parameter. Our theoretical analysis is consistent with assignment of its symmetry to an L = 3 odd parity state for which one of the three thermodynamic phases in non-zero magnetic field is chiral.
Highlights
Recent interest in topological superconductors has focused attention on materials that exhibit chiral symmetry, or have been proposed to exhibit chiral symmetry, including Sr2RuO4, 3He, and UPt3 [1]
The diffraction patterns were constructed from a superposition of scattering images measured at different rocking angles φ as the sample and magnet are tipped about a horizontal axis perpendicular to the neutron beam
The distortion of the vortex lattice (VL) from a perfect hexagon is a result of penetration depth anisotropy in the plane perpendicular to a*
Summary
Recent interest in topological superconductors has focused attention on materials that exhibit chiral symmetry, or have been proposed to exhibit chiral symmetry, including Sr2RuO4, 3He, and UPt3 [1]. Josephson tunneling interference measurements [10] and measurements of the polar Kerr effect [11] provide evidence for an order parameter that is chiral in the B-phase. We use small angle neutron scattering (SANS) from the vortex lattice (VL) to provide a bulk probe of the temperature dependence of the penetration depth, obtaining evidence for the nodal structure of the order parameter in the Bphase supporting its identification as an odd parity, chiral state, with E2u symmetry consistent with theory [12]
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