Zero electrical resistance is a rare occurrence in condensed matter physics, with superconductivity and quantum Hall effect being prime examples. However, a few years ago it was unexpectedly found that a pure two-dimensional conductor, also known as a quantum Hall system (QHS), can be driven to a zero-resistance state by microwave radiation.

Here we report on a state which is characterized by a zero-differential resistance. This state emerges under very similar conditions with one important difference: instead of microwave radiation, the QHS is subject to a modest dc electric field.

Theoretically, both states can be linked to the underlying negative (total or differential) resistance and its instability, which forces the conductor to break into current domains. While in irradiated systems the domain currents still remain experimentally elusive, they are directly available from these new experiments which offer exciting opportunities to explore electrical instabilities associated with these exotic states.

Zero differential resistance in quantum Hall systems Michael A. Zudov, University of Minnesota – Twin Cities, DMR 0548014

Hatke, Chiang, Zudov, Pfeiffer, West, Physical Review B - Rapid Commun. 82, 041304(R) (2010)

(a) Differential resistivity measured at magnetic field B = 1.3 kG and temperature T = 1.5 K is equal to zero within a finite current range. (b) Current-voltage characteristic shows a plateau within the same current range. This behavior disappears at lower B and higher T.

Education:Graduate students: W. Zhang, Hung-Sheng Chiang, Anthony Hatke, Kevin Christie, Brandon Fosso, Boyi Yang

Undergraduate students:Nicholas Eggert (2006-2007)Emily Gras (2007 NSF REU program) Bryan Perfetti (2007-2008 UROP Program)Matthew Bryan, (2009 UROP Program) Students received training in cryogenic, vacuum, and microwave technologies, semiconductor nanofabrication, measurement techniques, data acquisition and analysis, scientific programming, and web development. To date, students delivered twelve presentations about their research at conferences, seminars, and Open House events for incoming students. Students significantly contributed to the development of the group website (see below) aimed to convey the basics of our research to a broad audience.

Societal Impact:Understanding electronic devices based on GaAs, one of the most technologically important semiconductors, contributes to advances in material science and device fabrication, making possible applications ranging from fast transistors for cellular phones to lasers for compact disc players.

Project results were reported at:HMF-19, Fukuoka, Japan (2010); ICPS-30, Seoul, Korea (2010); Nanostructures, St. Petersburg, Russia (2010); QHE@30, Minneapolis, MN (2010, co-organized by a PI); Semicond. Winter School, Yekaterinburg, Russia (2010); NHMFL, Tallahassee, FL (2009); IMS NRC, Ottawa, Canada (2009); EP2DS-18, Kobe, Japan (2009); EPQHS-3, Capannori, Italy (2009); NEST-INFM & Scuola Normale Superiore, Pisa, Italy (2009); Universitat Karlsruhe, Karlsruhe, Germany (2009); Russian Academy of Sciences, Russia (2009); HMF-18, Sao Pedro, Brazil (2008); NanoPeter, St. Petersburg, Russia (2008), 2010); QPEQHS, MPIPKS, Dresden, Germany (2008); Forschungszentrum, Karlsruhe, Germany (2007); EP2DS-17, Genova, Italy (2007); EPQHS-2, State College, Pennsylvania (2007); QHYST06, MPIPKS, Dresden, Germany (2006); APS March Meetings (2007-2010); Universities: Rice (2008), Wisconsin (2008), Utah (2009), Minnesota (2006, 2009)

http://groups.physics.umn.edu/zudovlab/

Zero differential resistance in quantum Hall systems Michael A. Zudov, University of Minnesota – Twin Cities, DMR 0548014