MRS Bulletin

Technical Feature

Technical Feature

Two-Dimensional Electron Gases at Oxide Interfaces

J. Mannhart, D.H.A. Blank, H.Y. Hwang, A.J. Millis and J.-M. Triscone


Two-dimensional electron gases (2DEGs) based on conventional semiconductors such as Si or GaAs have played a pivotal role in fundamental science and technology. The high mobilities achieved in 2DEGs enabled the discovery of the integer and fractional quantum Hall effects and are exploited in high-electron-mobility transistors. Recent work has shown that 2DEGs can also exist at oxide interfaces. These electron gases typically result from reconstruction of the complex electronic structure of the oxides, so that the electronic behavior of the interfaces can differ from the behavior of the bulk. Reports on magnetism and superconductivity in oxide 2DEGs illustrate their capability to encompass phenomena not shown by interfaces in conventional semiconductors. This article reviews the status and prospects of oxide 2DEGs.

Jochen Mannhart can be reached by e-mail at [email protected]

Mannhart has been a Chaired Professor of Physics at the Center for Electronic Correlations and Magnetism at the University of Augsburg since 1996. He holds a diploma in physics from the University of Tübingen, Germany. Mannhart later received his PhD degree for imaging the Josephson current in tunnel junctions, also at Tübingen. Starting in 1987, he worked as a visiting scientist at the IBM T.J. Watson Research Center in Yorktown Heights, and as a research staff member at the IBM Zurich Research Laboratory in Rüschlikon, Switzerland. Mannhart's interests focus on the properties of interfaces in complex electronic materials. The efforts of the various teams he has worked with have resulted in the development of bicrystal Josephson junctions and SQUIDs, the enhancement of grain boundary critical current density in high-Tc superconductors by grain alignment, and the fabrication of the first all-oxide FETs. Mannhart is a fellow of the Institute of Physics and of the American Physical Society. In 2008, he was awarded the Gottfried Wilhelm Leibniz-Preis of the German Science Foundation.

Dave H.A. Blank can be reached at MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE, The Netherlands; tel. 31-53-489-3121; and e-mail [email protected]

Blank is a professor in chemistry and materials science at University of Twente, The Netherlands. He received his PhD degree in applied physics on high temperature superconductors. In 2007, Blank became the scientific director of MESA+ Institute for Nanotechnology, The Netherlands. The major focus of his research is growth studies, deposition and structuring techniques, and properties of (artificial) complex materials, especially oxides. In his group, the first time-resolved RHEED-system is developed. In 2002, Blank was awarded with the VICI laureate of the Dutch Science Foundation for his work on artificial materials for nanoscale devices. In 2004, he became the flagship captain of nano-electronic materials science of the NANONED program (the Dutch initiative on nanotechnology).

Harold Y. Hwang can be reached at the University of Tokyo, Interdisciplinary Science Building 606, 5-1-5 Kashiwano-ha, Kashiwa-shi, Chiba 277-8561, Japan; and e-mail [email protected]

Hwang is an associate professor in the Department of Advanced Materials Science and the Department of Applied Physics at the University of Tokyo, and with the Japan Science and Technology Agency. He received a BS degree in physics, BS and MS degrees in electrical engineering from the Massachusetts Institute of Technology (1993), and a PhD degree in physics from Princeton University (1997). Hwang was formerly a Member of the Technical Staff in the Materials Physics Research Department at Bell Laboratories, and a visiting professor at the Institute for Chemical Research, Kyoto University. His research interests include charge transport, spin and lattice dynamics, ordering transitions in transition metal oxides, and the atomic engineering of oxide heterointerfaces. Hwang received the 2005 MRS Outstanding Young Investigator Award, and was a meeting chair for the 2007 MRS Spring Meeting.

Andrew J. Millis can be reached by e-mail at [email protected]

Millis is a professor of physics and department chair at Columbia University. Before joining Columbia, he was on the faculty of Rutgers and Johns Hopkins Universities, and also worked for 10 years in the Theoretical Physics Research Department at AT&T (later Lucent) Bell Labs. His research is in the area of theoretical condensed matter physics. Millis is known for his work on “heavy fermion” materials, on quantum criticality, on colossal magnetoresistance manganites, and on high-temperature superconductivity.

Jean-Marc Triscone can be reached at DPMC, University of Geneva, 24 quai E.-Ansermet, 1211 Geneva 4, Switzerland; tel. 41-22-379-6651; and e-mail [email protected]

Triscone is a professor of physics in the Condensed Matter Physics Department at the University of Geneva, leading a group working on nanoscale studies of ferroelectrics, field effects in correlated oxide systems, and oxide interface physics. Triscone obtained his PhD degree in 1987 with professor Oystein Fischer, studying metallic superconducting superlattices. In 1990, 1991, and 1995, he was a visiting scientist at Stanford University. Since 1996, Triscone has been a full professor at Geneva. Between 2001 and 2007, he was the deputy-director of the National Center of Competence in Research MaNEP. Since July 2007, Triscone has been the Dean of the Faculty of Sciences at Geneva. With D. Blank and J. Mannhart, he is lead ing the European Science Foundation network Thin Films For Novel Oxide Devices (THIOX). In addition, Triscone has been an APS fellow since 2006.