CM/BIO/ECE Seminar Series

Wednesday, September 20, 2017 4:00pm

Physics Library, Room 223A, Physics Building


physics bldg

Sayantika Bhowal, MU Physics & Astronomy Dept., presents, "Study of Spin-Orbit Coupling Induced Emergent Phenomena in Strongly Correlated Systems." Refreshments will be served beginning at 3:30pm.

Strongly correlated systems form a broad group of versatile materials, the understanding of which is one of the greatest challenges in the present day condensed matter research. Recently the thrust in oxide research has been extended to 5d transition metal oxides (TMOs) where spin-orbit coupling (SOC) plays an important role. In my talk, I will discuss about 5d TMOs, particularly iridates with various electron filling. We show that in d5 hexagonal iridate Ba3IrTi2O9, the spin-orbit entangled jeff=1/2 pseudo-spin states, which are arranged on a frustrated triangular network, lead to bond dependent Kitaev interactions. In contrast, another member of this family

Ba3TiIr2O9 containing Ir-Ir structural dimer leads to weakly interacting spin-orbital singlet (SOS) states stabilizing a valence bond solid state.

Lowering the filling of d orbitals to d4 suggests an atomic non-magnetic J=0 ground state in the presence of strong SOC. This however breaks down in a series of double perovskite and 6H perovskite iridates primarily due to the band structure effect in a solid. Interestingly, the spontaneous moments thus generated at the Ir site in the 6H perovskite Ba3ZnIr2O9, lead to an exotic quantum spin-orbital liquid state owing to its unique crystal geometry. The surprise continues with further reduction of the filling to d3. In contrast to the common expectation of quenched orbital moment in a d3 system, SOC is found to be in action in these hexavalent double perovskite iridates. Our calculation shows that SOC together with strong Ir-O covalency reduces the spin moment at the Ir site and enhances the orbital moment in these d3 iridates.