Study of the Electronic Structure of Sr2IrO4 Bulk Crystals and Thin Films

11:00 AM - 12:00 PM
John Nichols, The University of Kentucky, Lexington
Materials Science and Technology Division Seminar
Chemical and Materials Sciences Building (4100), Room J-302
Email: Ho Nyung Lee

There has been recent interest in 5d transition metal oxides due to their potential for exotic electronic states. These materials were anticipated to be paramagnetic metals due to weak electron correlation, resulting in more spatially extended electrons than in their 3d and 4d counterparts. However, recent experimental studies on single crystals have shown that Sr2IrO4 is a magnetic insulator that has a novel Jeff = ½ Mott ground state with canted antiferromagentic ordering below 240 K. This behavior is attributed to strong spin-orbit coupling with energy comparable to the on-site Coulomb interaction and the crystal field energy. I will present our recent results of scanning tunneling microscopy (STM) on single crystals in addition to transport and optical properties on thin-films of Sr2IrO4. Low temperature (77 K) STM measurements reveal an energy gap of 615 meV and an anomalous magnon feature. In addition, measurements on epitaxial Sr2IrO4 thin-films have shown that although the electronic structure of this system is sensitive to strain and a-site substitution, the bandwidth and effective correlation energy adjust in a manner to prevent full gap closing.


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