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[CMT SEMINAR] Ipsita Mandal – Some aspects of correlated electrons

2019-09-03 @ 11:00 - 12:00

Speaker: Ipsita Mandal
Affiliation: University of Stavanger,
Title: Some aspects of correlated electrons,
Time:  Fika 10:30-11:00 , Seminar 11:00-12:00,
Place: Nordita South, room 112:028 .

In this talk, I am going to present exciting results from two of my ongoing/recent projects.
First part:
Spin-orbit coupling (SOC) assisted (spin j = 1/2) Mott insulators exhibiting bond-directional exchange interactions are expected to exhibit unconventional quantum magnetic phases like spin liquids [1, 2] predicted by the Kitaev model, dubbed as Kitaev spin liquid (KSL). The feature of a Kitaev material is that the Kitaev coupling is the dominant exchange coupling. Compounds like honeycomb iridates and α-RuCl_3 have been identified as candidate Kitaev materials. In the first part of my talk, I will address the unresolved question whether α-RuCl_3 is actually a Kitaev material. If yes, what is the value of the Kitaev coupling strength? If not, what are the dominant terms in the effective spin Hamiltonian that can describe the system? We focus on the results from resonant torsion magnetometry experiments by Modic et al, which they can measured the magnetotropic coefficient k, when a magnetic field B is applied making angle θ with the c-axis of the crystal. Using a simple Hamiltonian with a dominant paramagnetic term, we will show that we can fit the data obtained in the experiments.
Second part:
In sufficiently clean metals, it is possible for electrons to collectively flow as a viscous fluid at finite temperature. These viscous effects have been predicted to give a notable magneto resistance, but whether the magnetoresistance is positive or negative has been debated. We argue that regardless of the strength of inhomogeneity, bulk magnetoresistance is always positive in the hydrodynamic regime.



11:00 - 12:00