Magnetism and superconductivity in two-sublattice periodic Anderson model for UTe2: effect of spin-orbit coupling

UTe2 is a strong candidate for a spin-triplet superconductor [1] because of its extremely large upper critical field exceeding the Pauli limit [1,2] and multiple superconducting phases induced by magnetic field or pressure [3].

The mechanism of superconductivity in UTe2 has been discussed based on the spin fluctuation mechanism. Magnetization measurement observes ferromagnetic fluctuation, however, neutron scattering experiments detect antiferromagnetic fluctuation [4]. Antiferromagnetic fluctuation usually mediates spin-singlet superconductivity rather than spin-triplet superconductivity.

We previously showed that spin-triplet superconductivity is stabilized rather than spin-singlet superconductivity even in the region of dominant antiferromagnetic fluctuation in a mixed-dimensional periodic Anderson model[5].

However, as various measurements show, UTe2 exhibits magnetic anisotropy [6], and the spin-orbit coupling may lift the degeneracy due to rotational symmetry in spin space.

In this study, we extend our model to include two sublattices and sublattice-dependent Rashba spin-orbit coupling and calculate the magnetic susceptibility and superconducting instability.

[1] Sheng Ran et al., Science 365, 684-7 (2019).

[2] Georg Knebel et al., J. Phys. Soc. Jpn. 88, 063707 (2019).

[3] Daniel Braithwaite et al., Commun. Phys. 2, 147 (2019).

[4] Chunruo Duan et al., Phys. Rev. Lett, 125, 237003 (2020).

[5] Ryuji Hakuno, Kosuke Nogaki and Youichi Yanase, Phys. Rev. B, 109, 104509 (2024).

[6] Hiroki Fujibayashi et al., J. Phys. Soc. Jpn. 92, 053702 (2023).