de Haas-van Alphen effect and Fermi surfaces in spin-triplet superconductor UTe2

Unusual superconducting properties with the spin-triplet state of UTe2 are one of the hottest topics in condensed matter physics[1]. We present our recent studies on the de Haas-van Alphen (dHvA) effect in UTe2 using ultra-clean single crystals (RRR=200-800) [2]. Two kinds of cylindrical Fermi surfaces, which correspond to the main hole and electron Fermi surfaces, are clearly detected. The angular dependence of the dHvA frequencies is in very good agreement with that calculated by GGA+U (U=2eV). The detected cyclotron effective masses are very large, ranging from 32 to 57m0, revealing the strong mass enhancement from the band masses. The results of dHvA experiments are in less agreement with those of the LDA calculation for ThTe2 based on the 5f^2 localized model, while the bare LDA calculation with the 5f^3 itinerant model predicts a Kondo semiconducting behavior, suggesting that UTe2 has a mixed valence state.

[1] See review article, for example, D. Aoki, J. P. Brison, J. Flouquet, K. Ishida, G. Knebel, Y. Tokunaga, and Y. Yanase, J. Phys.: Condens. Matter, 34, 243002 (2022).

[2] D. Aoki, H. Sakai, P. Opletal, Y. Tokiwa, J. Ishizuka, Y. Yanase, H. Harima, A. Nakamura, D. Li, Y. Homma, Y. Shimizu, G. Knebel, J. Flouquet, and Y. Haga, J .Phys. Soc. Jpn., 91, 083704 (2022).