The LaAlO3/SrTiO3 heterostructure is a potential candidate for a high mobility two-dimensional electron system with novel electronic and magnetic properties. Although LaAlO3 and SrTiO3 are both large-gap band insulators, the interface is conductive, and even superconducting below 200 mK. Negative electronic compressibility is observed as the carrier density is tuned through electric field effect [1]. Magneticordering has been proposed to arise from the d-electrons transferred by polarization discontinuity. However the magnetization of this system has not previously been studied, because of the small volume of the interface. Using torque magnetometry, we detect the magnetic moment of the interface system directly [2]. Our results indicate the existence of a magnetic ordering at the two-dimensional conductive interface. More importantly, the same magnetic behavior persists even when the sample is superconducting, which suggests an unconventional two-dimensional superconducting phase.

 

References:

[1] Lu Li, C. Richter, S. Paetel, T. Kopp, J. Mannhart, and R. C. Ashoori, Science 332, 825 (2011)

[2] Lu Li, C. Richter, J. Mannhart, and R. C. Ashoori Nature Physics 7, 762 (2011)

 

Biography：Prof. Lu Li received his B.S. in physics from USTC in 2002, and Ph.D. in physics from Princeton in 2008. He was a Pappalardo fellow at MIT from 2008 to 2011, and became an assistant professor in physics in the University of Michigan in 2011. His main research interests are the electronic transport studies of low dimensional materials including high Tc superconductors, Dirac fermion systems, and oxide interface.