When spin-orbit coupling meets with electron correlations

Date

Apr 2, 2019

Time

5:00 PM - 6:00 PM

Speaker

Prof. Dr. Hidenori Takagi

Affiliation

MPI FKF Stuttgart

Series

MPI-CPfS-TUD Gemeinsames Anorg.-Chemisches Kol.

Language

en

Main Topic

Chemie

Other Topics

Physik, Chemie

Host

Prof. Dr. S. Kaskel, Prof. Dr. M. Ruck, Prof. Dr. J. Weigand, Prof. Dr. C. Felser, Prof. J. Grin

Description

The exploration of novel phases of interacting electrons (correlated electrons) has long been a major stream of condensed-matter research. Many-body interactions among electrons give rise to a huge variety of phases, grouped into electron-solid, -liquid-crystal, -liquid and -gas states. The wealth of possibilities arises from a complicated interplay of lattice geometry, quantum effects and the multiple degrees of freedom of the electron (charge, spin and orbital). In the past, the two dominant areas of exploration have been the 3d transition-metal (TM) oxides and the 4f intermetallic compounds but recently 5d TM oxides and related compounds have emerged as the next arena of correlated-electron physics. Significant new physics is expected due to the presence of a large spin-orbit coupling in heavy 5d elements, tying together the otherwise independent spin and orbital degrees of freedom. This can be of order 0.5eV and is often larger than the crystal-field splitting of the orbital states, resulting in a spin-orbital-entangled state of correlated electrons. The nature of the spin-orbital entanglement depends significantly on the d-electron number and the chemical bonding, and it is anticipated that, in combination with electron correlations, a rich variety of novel electronic phases are waiting to be discovered. To name just a few, the proposed phases include Kitaev quantum spin liquids, correlated topological semimetals, excitonic magnets and multipolar-ordered states. In this talk, I will present our recent exploration of such exotic faces of spin-orbital entangled matter in 5d (and 4d) transition metal oxides. Topics will include the following. (I) Spin-orbital quantum liquid on honeycomb lattice in 5d5H3LiIr2O6 [1]. (II) Jeff = 0 Mott insulator [2] in 4d4 Ru4+ oxides and proximity to excitonic magnetism. (III) Multipolar ordering in 5d1 Ta4+ chlorides [3]. References [1] K. Kitagawa, T. Takayama, Y. Matsumoto, A. Kato, R. Takano, Y. Kishimoto, S. Bette, R. Dinnebier, G. Jackeli, and H. Takagi, Nature, 554, 341–345 (2018). [2] G. Khaliullin, Phys. Rev. Lett. 111, 197201 (2013). [3] H. Ishikawa, T. Takayama, R. Kremer, J. Nuss, R. Dinnebier, K. Kitagawa3, K. Ishii and H. Takagi, submitted.

Links

• MPI CPfS

Last modified: Apr 9, 2019, 2:08:38 AM