Day 3 :
Brookhaven National Laboratory, USA
Ivan Bozovic received his PhD in Solid State Physics from Belgrade University, Yugoslavia, where he was later elected a professor and the Physics Department Head. After moving to the USA in 1985 he worked at Stanford University, the Varian Research Center, and 1999-2002 in Oxxel, Bremen, Germany. Since 2003, he is the MBE Group Leader at Brookhaven National Laboratory, and since 2014 also an Adjunct Professor of Applied Physics at Yale University. He is a Member of European Academy of Sciences, Foreign Member of the Serbian Academy of Science and Arts, Fellow of APS, and Fellow of SPIE. He received the Bernd Matthias Prize for Superconducting Materials, SPIE Technology Award, the M. Jaric Prize, the BNL Science, and Technology Prize, was Max Planck and Van der Waals Lecturer and is a Gordon and Betty Moore Foundation PI. His research interests include basic physics of condensed states of matter, novel electronic phenomena including unconventional superconductivity, innovative methods of thin film synthesis and characterization, and nanoscale physics. He has published 11 research monographs and over 280 research papers, including 25 in Science and Nature journals.
Superconductivity in cuprates has many mysterious facets, but the most important question is why the critical temperature (Tc ) is so high. Our experiments target this question. We use atomic-layer-by-layer molecular beam epitaxy to synthesize atomically perfect thin films and multilayers of cuprates and other complex oxides. By atomic-layer engineering, we optimize the samples for a particular experiment. I will present the results of a focused and comprehensive study that took twelve years and over two thousand cuprate samples, perhaps without precedence in Condensed Matter Physics. We have measured the key physical parameters of the normal and superconducting states and established their precise dependence on doping, temperature, and external fields. This large data basis contains a wealth of information and constraints tightly the theory. One striking conclusion is that superconducting state cannot be described by the standard Bardeen-Cooper-Schrieffer theory, anywhere in the phase diagram. Next, the rotational symmetry of the electron fluid in the normal metallic state above Tc is always spontaneously broken-the so-called “electronic nematicity”-unlike in standard metals that behave like Fermi Liquids. Finally, the insulating state on the underdoped side is also unusual, with mobile charge clusters formed by localized pairs. All these features are quite exceptional, paint a new picture of high-Tc superconductivity in cuprates, and point to a new direction in search of new high-Tc superconductors.
University of Virginia, USA
Joseph Poon is William Barton Rogers Professor of Physics at the University of Virginia. He received his BS and PhD from Caltech and was did postdoc work at Stanford University. He has published 200+ papers. His current research is on magnetic films and thermoelectric materials. He previously worked on metallic glasses and quasicrystals.
Spintronics (SPIN TRansfer elecTRONICS) was introduced by SA Wolf in 1996 as the name of a DARPA project to develop both a non-volatile magnetoresistive random access memory (MRAM) and also magnetic sensors for specialized applications. Today, spintronics has already shown promise in ultra-low power and non-volatile information processing and data storage technology. A recent advance in spintronic material systems will be reviewed. For the rest of my talk, I will focus on amorphous rare-earth-transition-metal (a-RE-TM) thin films that exhibit perpendicular magnetic anisotropy (PMA). a-RETM are ferrimagnets with two ferromagnetic RE and TM sublattices that interact via antiferromagnetic exchange coupling. These amorphous ferromagnetic films exhibit large coercivity fields of several Tesla and moderate anisotropy energy ~106 erg/ cm. The magnetization of the sublattices compensates each other at the compensation temperature (Tcomp). The spin structure and atomic-scale structure support ultrafast magnetic switching and ultra-small ~5-10 nm skyrmions. These materials are being studied for high-density ultrafast nanoelectronics. Self-exchange bias can be obtained by appropriately configuring the nanoscale structure. The mechanisms are verified by micromagnetic and atomistic simulations. Measurements include magnetization, MOKE, MFM, Hall effect, and magneto-resistance. The ability to control these new properties in amorphous films without the need for epitaxial growth could open a new avenue for enhancing the functionalities of spin-based materials.