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July 26, 2018 - 10:00am
Shriram Building, Room 262

Ph.D. Candidate:  Qi Yang

Research Advisor:  Aharon Kapitulnik

Date: Thursday, July 26, 2018
Time: 10:00 am
Location: Shriram Building, Room 262

Title:  Proximity Effects between Topological Insulators and Insulating Ferromagnets

Thin films of topological insulators (TIs) Bi2Se3 and (BixSb1-x)2Te3 were deposited on the insulating ferromagnet EuS. While positive magnetoresistance was observed above the Curie temperature of EuS (TC ≈ 15 K) as ubiquitously obtained in TIs, a negative magnetoresistance emerges below TC. Additionally, in the case of (BixSb1-x)2Te3, when the Fermi level is close to the Dirac point and the bulk conduction is minimized (x = 0.05), sharp increases in sheet resistance were observed at T ≈ 30 K with decreasing temperature, coinciding with magnetic anomalies observed in AC susceptibility measurements. These suggest a two-stage gap-opening mechanism due to magnetic proximity.