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FIELD Computational Sciences
DATE February 20 (Wed), 2019
TIME 16:00-18:00
PLACE 1424
SPEAKER Bongjae Kim
HOST Kim, BeomHyun
TITLE Anisotropic magnetic interactions in transition metal oxide systems

Anisotropic magnetic interactions are found to play key roles in explaining many exotic properties in various types of transition metal oxides. In this talk, I will discuss two quasi-square net transition metal oxide systems: Sr2RuO4 and Sr2VO4. For Sr2RuO4, a candidate of chiral p-wave superconductor, we first access the possibility of proposed order parameter rotation in an external magnetic field of 200 Oe, and conclude that the spin-orbit interaction in this material is several orders of magnitude stronger than this hypothesis implies. Thus, the observed invariance of the Knight shift across Tc has no plausible explanation, and casts doubt on using the Knight shift as an ultimate litmus paper for the pairing symmetry. Then, quantitative double-exchange-like model, which combines itinerant fermions with magnetic interaction is proposed. This is complementary to the Hubbard-model-based calculations published so far, and forms an alternative framework for exploring superconducting symmetry in Sr2RuO4. For Sr2VO4, I will talk about highly competing exchange interactions in the system, which places the system at the crossover between XY- and Heisenberg model regime by involving non-negligible interlayer couplings. Interestingly, two-site exchange anisotropy is found to be strong which is relieved by the orthorhombic distortion induced by the spin-stripe order. If time allows, I will briefly talk about our recent results on RuCl3 – a prototypical Kitaev system.
Bongjae Kim, Sergii Khmelevskyi, I. I. Mazin, D. F. Agterberg, and Cesare Franchini, npj Quantum Materials 2 37 (2017).
Bongjae Kim, Sergii Khmelevskyi, Peter Mohn, and Cesare Franchini, Phys. Rev. B 96 180405(R) (2017)

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