Research Seminar of Prof Bruce D. McCombe from University at Buffalo

Lecture Time: 09:30 on 21th Oct., 2016

Lecture Room: C501 of National Science Park

Lecture Title: What's the g-factor in Narrow-gap-semiconductor Nanostructures?

Bruce D. McCombe

Department of Physics, University at Buffalo

The State University of New York

Buffalo, NY 14260, USA

Abstract

Spin effects in semiconductors have received a great deal of attention for well over a decade, in the context of Spintronics technology, which focuses on controlling intrinsic spin (rather than charge) of carriers in semiconductors to produce new/novel functionalities for faster and lower power integrated circuits. Manipulating spins is facilitated in materials having large Spin-Orbit interaction, which permits electric fields to be used for this purpose. I will provide some background and summarize the basic physics and ideas, and then describe our recent studies of the electron g-factor and its anisotropy in two samples having so-called “composite channels” in the InAs/InGaAs/InAlAs heterostructure system. We have measured the spin-splitting of two-dimensional electrons in Landau Levels at low temperatures and in magnetic fields up to 10 T by magneto-transport and THz magneto-photoconductivity. Both the magnitudes of the experimental g-factors with the field along the quantization axis and their anisotropies (ratio of g-factor with B parallel to that with B perpendicular to the quantization axis) are at least a factor of two larger than the corresponding calculated single particle values. We find that the many-body exchange contribution and its angular dependence (proportional cosθ, withθthe tilt angle) must be taken into account to understand this behavior. In addition, we find evidence for an apparent vanishing of the exchange contribution at large tilt angles for the high mobility sample. The low mobility sample shows the expected cosθdependence. I will provide some insight into this behavior based on recent theoretical work.

Work supported in part by NSF-MWN 1008138

Biography

Education

Bowdoin College, Brunswick, Maine; 1956-60

A.B. (cum laude, Phi Beta Kappa); 1960

Brown University, Providence, Rhode Island; 1960-65

Ph.D. (Sigma Xi); 1966

Honors, Awards and Other Recognition

Brown University Fellowship, 1960-62

NSF Fellowship, 1962-65

NRC-NRL Postdoctoral Research Associate, 1967-69 (competitive award)

Best Technical Paper Award, Solid State Division, Naval Research Laboratory, 1969 and 1972

National Academy of Sciences-National Research Council Ad Hoc Committee on Electrical Properties, 1970

Naval Research Laboratory RESA (Research Society of America) Pure Science Award, 1972 (Award given each year in Pure and Applied Science)

Selected for NRL Sabbatical Study Program, 1972-73 (competitive, with typically only one to four scientists per year receiving the award)

Outstanding Performance Ratings, NRL, 1970, 1972, 1977 and 1978

National Academy of Sciences, Ad Hoc Panel on High Magnetic Field Research and Facilities; Chairman,

Facilities Subpanel (1979); co-author of report

Elected to Fellowship, American Physical Society, Division of Condensed Matter Physics, 1981

Elected to Membership in the New York Academy of Sciences in 1982.

Elected Member at Large, Executive Committee, Division of Condensed Matter Physics, APS, 1982-84; Chairman, Fellowship Committee

Panel Member, NAS-NRC Panel on Artificially Structured Materials; co-author of Report, 1985

Invited Participant, USSR Academy of Sciences, USSR/USA Seminar on 2D Electronic Systems, May 29-June 3, 1988 (one of 10 US scientists invited to visit Chernogolovka and the Inst. for Solid State Physics; this was the first visit of western scientists to this formerly closed institution – It was written up in Physics Today)

UUP Excellence Award, SUNY at Buffalo, May 1990.

Invited Participant - Symposium on "The Advancing Frontiers of Condensed Matter Science", Univ. of Pennsylvania, Oct. 13-14, 1997 (unable to attend due to teaching commitments).

FNSM Dean's Award for Excellence in Teaching, June, 1998.

SUNY Distinguished Professor, October, 2001.

Invited Visiting Professor, Institut National des Champs Magnetiques Pulses, INSA, Universite Paul Sabbatier, Toulouse France, Summer, 2001.

Invited to be Roentgen Visiting Professor at the University of Wuerzburg for the summer of 2002 (declined due to other commitments)

IMR/CAMR Distinguished Visiting Scientist, NRC Ottawa, CA, April, 2004.

Visiting Scientist, Institute for Applied Physics, University of Hamburg, Germany, May, 2004.

Visiting Scientist, Grenoble High magnetic field Laboratory, Grenoble, France, June 2004.

Visiting Scientist, Humboldt Universitaet zu Berlin, Department of Physics, Novel Materials: May, 2011, December, 2011, September 2012, June 2013, May, 2014.

UB President's Medal, Given in recognition of "extraordinary service to the university", Awarded at Commencement, May 2012

Invited Speaker/participant at the 6th Science Conclave, Indian Institute of Information Technology, Allahabad, India, December 8 - 14, 2013.

Visiting Scientist, TU Wien, May 2 - May 9, 2014.

Membership in Technical Societies

APS, Division of Condensed Matter Physics (Fellow);

Materials Research Society;

Sigma Xi-RESA (Naval Research Laboratory Chapter)

Research Interests

Infrared and far infrared properties of semiconductors; magneto-optical and magneto-

transport studies of semiconductors; photoluminescence and Optically Detected Resonance(ODR) spectroscopy of semiconductors, semiconductor heterostructures, and low-dimensional semiconductor structures; many-body effects in low-dimensional semiconductor systems; physics of semiconductor nanostructures; electron-optical-phonon interaction in semiconductor nanostructures; effects of confinement on impurities in semiconductor nanostructures; excitons in semiconductor nanostructures; far IR studies of high pressure effects on electronic states in semiconductors and semiconductor nanostructures; IR and far IR nonlinear optics in semiconductors; electronic materials characterization; Spintronics, spin-orbit interaction in narrow gap semiconductor nanostructures, III-V magnetic semiconductors, magnetotransport and magnetic properties, spin-injection (optical studies) and THz spin manipulation; physics and applications of monolayer 2D semiconductors.

Professional Positions

NRC-NRL Postdoctoral Research Associate, Naval Research Laboratory, 1965-67

Research Physicist, GS-12, Semiconductors Branch, Naval Research Laboratory1967-70

Section Head, GS-13 and GS-14, Semiconductors Branch, NRL 1970-74

Sabbatical leave: Visiting Scientist, Max Planck Inst. fur Festkorperforschung, Stuttgart, W. Germany, October,1972 -October, 1973

Head, Semiconductors Branch, NRL, 1974-80

Superintendent, Electronics Technology Division, NRL, 1980-82

Adjunct Professor of Physics, State University of New York at Buffalo, 1978-82

Professor, Department of Physics and Astronomy, State University of New York at Buffalo, 1982-present

Associate Chairman, Department of Physics, State University of New York at Buffalo, 1984-87

Chairman, Department of Physics, September 1987- January 1996

Co-Director, Center for Electronic and Electro-Optic Materials, 1986 - 1997

Deputy Director, Institute on Superconductivity, SUNY at Buffalo, July 1987-July 1988

Gastprofessor, Institut fur Physik, Montanuniversität Leoben, Leoben, Austria, February - July, 1995

Director, Center for Advanced Photonic and Electronic Materials, 1997 - 2002.

Director, Center for Spin Effects and Quantum Information in Nanostructures, 2002 - 2007

Associate Dean for Research and Sponsored Programs, College of Arts and Sciences, August 2000 - July, 2003.

SUNY Distinguished Professor, Oct., 2001 - present

Adjunct Professor of Electrical Engineering, 2003 - present.

Vice Provost for Graduate Education and Dean of the Graduate School, January 2005 - June 2006

Interim Dean, College of Arts and Sciences, July 2006 - April, 2007.

Dean, College of Arts and Sciences, April 2007 - June 30, 2011.

Interim Provost and Exective Vice President, University at Buffalo, January 1, 2011 - May 31, 2012

Senior Advisor to the President, University at Buffalo, June 1, 2012 - July 27, 2012.

SUNY Distinguished Professor Emeritus, Research Professor, September 1, 2014 - present.