Multiorbital Hubbard systems with Hund coupling exhibit a sharp
crossover, as a function of filling or interaction, between a
conventional metal state and a non-Fermi liquid metal state with frozen
magnetic moments. The fluctuating local moments at the border of this
spin-frozen regime induce an instability to a spin-triplet
superconducting phase [1]. In multiorbital systems with effectively
negative Hund coupling, there is a closely related orbital freezing
phenomenon, which is connected to an unconventional type of spin-singlet
superconductivity realized in fulleride compounds [2]. In this talk, I
will use dynamical mean field simulations to illustrate and discuss
these phenomena. By a suitable basis transformation, one can even
connect the d-wave superconducting instability in the 2D Hubbard model
to a spin-freezing phenomenon [3].

[1] S. Hoshino and P. Werner, Phys. Rev. Lett. 115, 247001 (2015)
[2] K. Steiner, S. Hoshino, Y. Nomura, and P. Werner, Phys. Rev. B 94, 075107 (2016)
[3] P. Werner, S. Hoshino, and H. Shinaoka, Phys. Rev. B 94, 245134 (2016)

連絡教員　物理学系　古賀　昌久（内線2727）