Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session F50: Experimental Advances on Newly-Discovered Unconventional Superconductor UTe2Invited Session Live
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Sponsoring Units: DCMP Chair: Priscila Rosa, Los Alamos National Laboratory |
Tuesday, March 16, 2021 11:30AM - 12:06PM Live |
F50.00001: Band structure and local electronic correlations in triplet superconductor UTe2 Invited Speaker: Lewis Wray The compound UTe2 has recently been found to realize spin triplet superconductivity from a non-magnetic normal state. This has sparked intense research activity, including analyses that suggest the superconducting order parameter to be topologically nontrivial. However, the electronic band structure and local correlations that underlie these phenomena are challenging to attribute with out direct measurements. I will present high resolution angle resolved photoemission (ARPES) measurements covering multiple planes in the 3D Brillouin zone of UTe2, revealing distinct Fermi pockets from two light electron bands and one heavy band. I will also present data showing atomic multiplet excitations and signatures of electronic symmetry, as a further basis for discussing many-body ordering instabilities. |
Tuesday, March 16, 2021 12:06PM - 12:42PM Live |
F50.00002: Intermediate valence UTe2 under pressure Invited Speaker: Sean Thomas Spin-triplet superconductors are a promising route in the search for topological superconductivity, and UTe2 is a recently discovered contender. Electrical resistivity, ac calorimetry, and x-ray absorption measurements of UTe2 under applied pressure reveal an antiferromagnetic quantum critical point near a critical pressure of 1.3 GPa. The emergence of magnetism is accompanied by an increase in valence toward a U4+ (5f2) state, which indicates that UTe2 exhibits intermediate valence at ambient pressure. At the end of the talk I will discuss new insights learned from dilatometry measurements as well as outstanding open questions regarding superconductivity in this material. |
Tuesday, March 16, 2021 12:42PM - 1:18PM Live |
F50.00003: Point Node Gap Structure of Spin-Triplet Superconductor UTe2 Invited Speaker: Tristin Metz Low-temperature electrical and thermal transport, magnetic penetration depth, and heat capacity measurements were performed on single crystals of the actinide superconductor UTe2 to determine the structure of the superconducting energy gap. Heat transport measurements performed with currents directed along both crystallographic a and b axes reveal a vanishingly small residual fermionic component of the thermal conductivity. The magnetic field dependence of the residual term follows a rapid, quasilinear increase consistent with the presence of nodal quasiparticles, rising toward the a-axis upper critical field where the Wiedemann-Franz law is recovered. Together with a quadratic temperature dependence of the magnetic penetration depth up to T/Tc = 0.3, these measurements provide evidence for an unconventional spin-triplet superconducting order parameter with point nodes. Millikelvin specific heat measurements performed on the same crystals used for thermal transport reveal an upturn below 300 mK that is well described by a divergent quantum-critical contribution to the density of states (DOS). Modeling this contribution with a T−1/3 power law allows restoration of the full entropy balance in the superconducting state and a resultant cubic power law for the electronic DOS below Tc, consistent with the point-node gap structure determined by thermal conductivity and penetration depth measurements. |
Tuesday, March 16, 2021 1:18PM - 1:54PM Live |
F50.00004: Multiple superconducting phases and field-induced phenomena in spin-triplet superconductor UTe2 Invited Speaker: Dai Aoki We present our recent results on the novel spin-triplet superconductor UTe2, which is at the verge of the ferromagnetic order. The huge upper critical field exceeding the Pauli limit indicates the spin-triplet state. For the field along b-axis, the field reentrant superconductivity is observed up to Hm~35T, where the first order metamagnetic transition occurs. The field reentrant superconductivity in UTe2 is similar to that observed in ferromagnetic superconductors, namely URhGe and UCoGe. Applying the pressure in UTe2, the superconducting transition temperature splits and the mulitple superconducting phase is detected in the AC calorimetry measurements as a thermodynamic response. We overview the results on UTe2 comparing with ferromagnetic superconductors, and show our perspective. This work was done in collaboration with G. Knebel, A. Pourret, J.P. Brison, D. Braithwaite, Q. Niu, M. Valiska, J. Flouquet, A. Nakamura, F. Honda, Y. Homma, D.X,Li, Y. Shimizu, Y. J. Sato, A. Miyake, S. Imajo, S. Kohama, M. Tokunaga, H. Harima, W. Knafo, I. Sheikin, C. Paulsen, Y. Tokunaga, S. Kambe, H. Sakai, S. Fujimori, K. Ishida, G. Nakamine, S. Kitagawa. |
Tuesday, March 16, 2021 1:54PM - 2:30PM Live |
F50.00005: Spin-triplet superconducting state in the nearly ferromagnetic compound UTe2 Invited Speaker: Sheng Ran Our recent discovery of the novel spin-triplet superconductivity in UTe2 has inspired a lot of interests in the community. Superconducting state of UTe2 closely resembles that of ferromagnetic superconductors, but the normal state is paramagnetic and shows no indication of magnetic ordering. UTe2 exhibits an extremely large, anisotropic upper critical field Hc2, temperature independent NMR Knight shift in the superconducting state, and a large residual normal electronic density of states. All these results strongly indicate that the superconductivity in UTe2 is carried by spin-triplet pairs. Even more striking, superconductivity reenters in the magnetic field of 45 tesla and persists up to 65 tesla, which is the upper limit of magnetic field in our current study. These extreme properties reflect a new kind of exotic superconductivity rooted in magnetic fluctuations and quantum dimensionality. |
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