Electronic phase behavior in spin-orbit Mott materials

Stephen Wilson, Boston College, DMR 1056625

Our group is currently working to explore an exciting new frontier in complex oxides where spin orbit coupling and correlation effects conspire to stabilize new electronic phases. A leading example of this are spin-orbit Mott phases found within several classes of correlated iridates. Debate however remains as to whether these systems are trivial band or Mott insulators. Our work with collaborators has shown that the electronic gap in one such compound Sr3Ir2O7 is much larger than expected and necessarily driven by the Coulomb interaction in a Mott ground state [1]. We have also established universalities among the magnetic and structural phase behaviors of the two prototypical spin-orbit Mott materials Sr2IrO4 and Sr3Ir2O7 [2]. Combined our results establish these correlated iridates as promising platforms for the future discovery of novel correlated electronic phases in presence of strong spin-orbit interactions.

Ref. [1]: Yoshinori Okada, W. Zhou, D. Walkup, Chetan Dhital, Ziqiang Wang, Stephen D. Wilson, and V. Madhavan, “Imaging the evolution of metallic states in a spin-orbit interaction driven correlated iridate” Nature Materials 12, 707 (2013). Ref. [2]: Chetan Dhital, Tom Hogan, Z. Yamani, Clarina de la Cruz, Xiang Chen, Sovit Khadka, Zhensong Ren, and Stephen D. Wilson, “Neutron scattering study of correlated phase behavior in Sr2IrO4” Physical Review B 87, 144405 (2013).

Fig. 1: Scanning tunneling spectroscopy data showing electronically inhomogenous ground state of Sr3Ir2O7 showing localized regions of small gap states residing within the larger insulating background [1].

Fig. 2: (left panel) Neutron scattering data showing the universality of antiferromagnetic phase behavior between classes of correlated iridates, Sr2IrO4 and Sr3Ir2O7 (right panel) Neutron data showing the presence of a high temperature distortion in Sr2IrO4 paralleling that of Sr3Ir2O7 [2].

Electronic phase behavior in spin-orbit Mott materials

Stephen Wilson, Boston College, DMR 1056625Our group continues to provide research experience and exposure for undergraduate physics majors in hope of retaining them within STEM career pathways. In the current year, my group hosted 4 unique undergraduate interns in our lab. Two participated during the spring and fall semesters and two during the summer of 2013 (1 of which comes from an underrepresented African American demographic).

I also continued my partnership with The Educational Cooperative through hosting another high school intern within my lab during the summer of 2013. Radha conducted a research project in support of the grant and obtained her first exposure in a modern science lab.

Also, I continued to work in training the next generation of neutron scattering experts by lecturing at the NCNR neutron summer school as well as sending a graduate student to the Argonne/ORNL neutron summer program.

Fig. 3: High school intern Radha Mastandrea working in the PI’s lab during the summer of 2013