Characterising the magnetic anisotropy of UTe₂

Unconventional superconductors could play a crucial role in developing topological quantum computing. A potential component for this development are spin-triplet superconductors, which are characterised by electron pairs with an odd wave function in a spin-1 state. Helium-3 is the only known realisation of this state, calling for a search of bulk materials that can host spin-triplet superconductivity. UTe₂, a heavy-fermion that superconducts at 1.6 K [1], has emerged as a promising candidate [2]. However, the two zero-field superconducting transitions that have been taken as evidence for a two-component order parameter [3] have recently been related to sample inhomogeneities [4].

In order to determine the intrinsic nature of UTe₂, we select small single crystals using focused ion beam (FIB) lithography and measure the magnetotropic coefficient [5] as a function of temperature and magnetic field. Similar measurements at larger magnetic fields will allow us to completely characterise the magnetic anisotropy, and help us gain a better understanding of the interplay between the magnetism in UTe₂ and its exotic superconducting phases.

[1] Ran, Sheng, et al. "Nearly ferromagnetic spin-triplet superconductivity." Science 365.6454 (2019): 684-687.

[2] Ran, Sheng, et al. "Extreme magnetic field-boosted superconductivity." Nature Physics 15.12 (2019): 1250-1254.

[3] Hayes, Ian M., et al. "Weyl superconductivity in UTe2." arXiv preprint arXiv:2002.02539 (2020).

[4] Thomas, Sean Michael, et al. "Spatially inhomogeneous superconductivity in UTe 2." Physical Review B 104.22 (2021): 224501.

[5] Modic, Kimberly A., et al. "Resonant torsion magnetometry in anisotropic quantum materials." Nature communications 9.1 (2018): 1-8.