Magnetization in the superconducting state of UPt3from polarized neutron diffraction

Abstract

The heavy-fermion superconductor UPt3 is thought to have odd parity, a state for which the temperature dependence of the spin susceptibility is an important signature. In order to address conflicting reports from two different experiments, the NMR Knight shift and measurements of the anisotropy of the upper critical field, we have measured the bulk susceptibility in a high-quality single crystal using polarized neutron diffraction. A temperature-independent susceptibility was observed for H||a through the transitions between the normal state and the superconducting A, B, and C phases, consistent with odd-parity, spin-triplet superconductivity.

Spin susceptibility of the topological superconductor UPt3 from polarized neutron diffraction

“…In previous work we measured the magnetic susceptibility with H ⊥ c using polarized neutron scattering for a UPt 3 crystal with high purity, residual resistance ratio (RRR) of 600 and mass 15 g. 36 We found that the spin susceptibility is temperature independent in the superconducting state for this orientation consistent with Knight shift results. 10,11 Here we extend these measurements for H||c with a smaller crystal, 0.4 g, of even higher purity grown at Northwestern University (RRR = 900), 18 for which a strong temperature dependence of the susceptibility is expected from the E 2u theory for odd-parity superconductivity with angular momentum locked to the c-axis.…”

“…In Fig. 4(a), reproduced from our earlier work, 36 we show the complete temperature dependence of the susceptibility from neutron scattering at 1.0 T along our SQUID measurements including earlier susceptibility measurements from Frings et. al.…”

“…37 The bulk magnetization was determined by measuring the neutron spin-flipping ratio R at the (1,0,0) nuclear Bragg reflection as described in more detail in previous work. 18,36 Here, R is defined as the ratio of scattering cross sections for incident neutrons with spins parallel and antiparallel to the applied magnetic q FIG. 3.…”

Nodal gap structure and order parameter symmetry of the unconventional superconductor UPt3

“…Our sample consists of a high-quality, 15 g single crystal (RRR > 600), cut into two pieces, and is described by Gannon et al [20]. The UPt 3 crystals were co-aligned, fixed with silver epoxy to a copper cold finger, and mounted to the mixing chamber of a dilution refrigerator with the crystal a-axis vertical and the c and a * -axes in the horizontal plane.…”

Polar Kerr effect studies of time reversal symmetry breaking states in heavy fermion superconductors

“…A number of experimental observations are consistent with E 2u pairing symmetry. Muon and 195 Pt Knight shift studies [58,59], as well as polarized neutron diffraction measurements [60], suggest spin-triplet pairing with parallel spins in the ab-plane. Direction-dependent thermal conductivity [61,62], Josephson interferometry [63,64], and vortex lattice [65,66] model of the order parameter [67].…”