Spin- and orbital-freezing in unconventional superconductors

Date

Nov 23, 2018

Time

2:00 PM - 3:30 PM

Speaker

Prof. Dr. Philipp Werner

Affiliation

University of Fribourg, Switzerland

Language

en

Main Topic

Materialien

Other Topics

Materialien

Host

Dr. Takashi Oka

Description

The phasediagrams of unconventional superconductors exhibit a superconducting dome below a non-Fermi liquid metal phase and next to a magnetically ordered insulator. In multiorbital systems with Hund coupling, these generic properties can be naturally explained by the phenomenon of spin-freezing [1], i.e. the appearance of disordered local moments in a certain filling and interaction regime. The fluctuating local moments at the border of the spin-frozen region produce the non-Fermi liquid behavior at elevated temperatures, and provide the glue for an unconventional spin-triplet pairing at low temperature [2]. Using appropriate mappings, one can connect this superconductivity to excitonic order in systems with crystal field splittings [3], and to the d-wave spin-singlet superconductivity in the two-dimensional Hubbard model [4]. In multi-orbital models with negative Hund coupling, which are relevant for fulleride superconductors, the role of spin and orbital is exchanged, and the unconventional spin-singlet pairing is induced by an orbital-freezing phenomenon [5]. I will also briefly discuss the connection between the spin-freezing regime of multi-orbital Hubbard models and the Sachdev-Ye model [6]. [1] P. Werner, E. Gull, M. Troyer and A. J. Millis, PRL 101, 166405 (2008) [2] S. Hoshino and P. Werner, PRL 115, 247001 (2015) [3] S. Hoshino and P. Werner, PRB 93, 155161 (2016) [4] P. Werner, S. Hoshino and H. Shinaoka, PRB 94, 245134 (2016) [5] K. Steiner, Y. Nomura, S. Hoshino, and P. Werner, PRB 94, 075107 (2016) [6] P. Werner, A. Kim, and S. Hoshino, arXiv:1805.04102 (2018)

Links

• MPI CPfS

Last modified: Nov 23, 2018, 1:06:40 AM