Speaker
Description
In 2019, unconventional superconductivity was observed in the heavy-fermion paramagnet UTe2 and a spin-triplet nature of the superconducting pairing has been proposed for this compound initially presented as a nearly-ferromagnet [1,2]. Soon after, multiple superconducting phases were found to develop near magnetic transitions in UTe2 under intense magnetic fields and high pressures [3-8].
Here, I will present a selection of results performed within a French-Japanese collaboration on UTe2. Experiments under combined extreme conditions showed that multiple superconducting phases can be induced by a magnetic field, sometimes coupled with pressure, in the vicinity of metamagnetic transitions [4,6,8] (see also [5,7]). From inelastic neutron scattering at zero magnetic field, we evidenced the presence of quasi-two-dimensional antiferromagnetic fluctuations in UTe2, which is also a two-legs magnetic ladder [9] (see also [10,11]). Their gapping in the zero-field superconducting phase indicates that these fluctuations may play a role in the superconducting mechanism [12-13].
Neutron scattering is a unique tool to microscopically unravel the role of magnetism, and particularly of the magnetic fluctuations, for the development of unconventional superconductivity in correlated-electrons materials. However, metamagnetism in UTe2 occurs at fields far beyond what is feasible today for inelastic neutron scattering (fields up to 36 T at ambient pressure, or up to 15-20 T under pressure may be needed). As perspectives, I will discuss how the extension of neutron techniques to higher magnetic fields, possibly coupled with very low temperatures and/or high pressures, will constitute a milestone to understand the interplay between magnetism and superconductivity in materials as UTe2.
[1] Ran et al., Science 365, 684 (2019).
[2] Aoki et al., J. Phys. Soc. Jpn. 88, 043702 (2019).
[3] Braithwaite et al., Commun. Phys. 2, 147 (2019).
[4] Knebel et al., J. Phys. Soc. Jpn. 88, 063707 (2019).
[5] Ran et al., Nat. Phys. 15, 1250 (2019).
[6] Knafo et al., Commun. Phys. 4, 40 (2021).
[7] Aoki et al., J. Phys. Soc. Jpn. 89, 053705 (2020).
[8] Valiska et al., Phys. Rev. B 104, 214507 (2021).
[9] Knafo et al., Phys. Rev. B 104, L100409 (2021).
[10] Duan et al., Phys. Rev. Lett. 125, 237003 (2020).
[11] Butch et al., npj Quantum Materials 7, 39 (2022).
[12] Duan et al., Nature 600, 636 (2021).
[13] Raymond et al., J. Phys. Soc. Jpn. 90, 113706 (2021).
