Colloquium: T.-C. Chiang

Title: Playing with Topological Insulators: Superconductivity and Strain Effects

Speaker: T.-C. Chiang, University of Illinois at Urbana-Champaign

Place: Room 201, Building 12, Yuquan Campus

Time: 14:00-15:00, April 20th (Friday) 

Abstract

Topological insulators are characterized by an inverted bulk band gap caused by a strong spin-orbit coupling. By analytic continuation, this gap must close at the surface and reopen outside in vacuum where the gap is noninverted (and infinite). The resulting metallic surface states, or topological states, are spin-polarized and span the bulk gap. They carry a surface spin current, largely independent of the details of the surface, which is a feature of strong interest for spintronic applications. This talk will focus on thin films of a prototypical topological insulator Bi2Se3 that are (1) made superconducting by proximity coupling to a simple superconducting substrate or (2) strained by stretching a flexible plastic film substrate. Angle-resolved photoemission and x-ray diffraction were employed to determine the electronic structure and the lattice structure. A novel flip-chip technique was employed to prepare epitaxial films of Bi2Se3 on the superconducting or flexible plastic substrates. We show how the topological surface states are modified under these conditions. Effects of superconducting pairing, coherence, bulk-surface coupling, and electron-lattice coupling will be discussed.

About the Speaker

EDUCATION

•    University of California at Berkeley (1973-1978), Ph.D. Physics

•    National Taiwan University (1967-1971), B.S. Physics

EMPLOYMENT

•   Research/Emeritus Professor (2011-), Professor (1988-2011), Associate Professor (1984- 1988), Assistant Professor (1980-1984), Department of Physics, University of Illinois at Urbana-Champaign

•    Associate Director (1999-2006), Head, Solid State Sciences and Materials Chemistry Program (1991-2006), Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign

•    Postdoctoral Research Associate, IBM T. J. Watson Research Center (1978-1980)

HONORARY AND VISITING APPOINTMENTS

•    Scientific Director, Synchrotron Radiation Center, University of Wisconsin-Madison (2010- 2014)

•    Distinguished Visiting Scholar, National Synchrotron Radiation Research Center, Taiwan (2013-2018)

•    Chair Professor, National Chiao-Tung University, Taiwan (2013-2016)

•    Honorary Chair, Tsing Hua University, Hsinchu, Taiwan, cosponsored by National Synchrotron Radiation Research Center (2008-2011)

•    Distinguished Chair, National Taiwan University, Taipei, Taiwan (2007-2010, 2015-2018)

•    Visiting Professor, ISSP, University of Tokyo (2016)

HONORS AND AWARDS

•    Academician, Academia Sinica, Taiwan (2016)

•    Davisson-Germer Prize, American Physical Society (2015)

•    Outstanding Alumnus, Physics Department, National Taiwan University, sponsored by the Space-time Forum - NTU Physics Alumni Association (2015)

•    Outstanding referee, American Physical Society (2008, inaugural group)

•    Fellow, American Physical Society (since 1986)

•    Xerox Faculty Award, University of Illinois (1985)

•    Presidential Young Investigator Award (1984-1989)

•    IBM Faculty Development Award, IBM T. J. Watson Research Center (1984 and 1985)