Description
- Abstract:
- Spin-orbit coupling (SOC) refers to the interaction between the orbital angular momentum and electron spin, which is typically a small perturbation in relative light elements. However, such interaction is proportional to the fourth order of the atomic number and could be quite significant for heavy elements. Exotic physics arising from significant SOC include the emergent phases in Mott insulators with strong SOC and the exploded works on topological insulators (TI). For the first research thread, the combined effects of strong electronic correlations with SOC can lead to a plethora of emergent novel quantum states. The second research thread which also involves strong SOC and correlated electrons lies at the intersection of topological insulator and Kondo insulator. In this thesis, we first present an extensive nuclear magnetic resonance (NMR) study of 23Na in Ba2NaOsO6, a typical Mott insulator with SOC. We measured 23Na NMR spectra as a function of temperature in different magnetic fields. The NMR measurements reveals a paramagnetic at high temperatures, a broken local point symmetry (BLPS) phase at intermediate temperatures and a canted ferromagnetic phase at low temperatures. Most importantly, we determine the field-temperature phase diagram of Ba2NaOsO6 which shows that the intermediate BLPS phase extends to wider range in high fields. Furthermore, by adopting numerical calculation, we confirm that the breaking of local point symmetry is not due to trivial intrinsic structure instability but is due to multipolar interaction. Next, angle dependence of NMR spectra show that the canted ferromagnetic order is suppressed along certain direction at low temperatures. Secondly, we performed NMR measurements of spin-lattice relaxation (T1) on 11B of Kondo insulator SmB6 at ultra-low temperatures in various magnetic fields. We observed constant low-energy density-of-states (DOS) which corresponds to gapless excitation.
- Notes:
- Thesis (Ph. D.)--Brown University, 2017
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Citation
Liu, Wencong,
"NMR Study of Materials with Significant Spin-Orbit Coupling and Transparent Oxide Films"
(2017).
Physics Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://doi.org/10.26300/gc5x-6p49
