Argonne National Laboratory

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Emergent Transport Phenomena in Low Dimensional Conductors, Superconductors and Correlated Electron Materials

Materials Science Seminar
Liuqi Yu, Florida State University
May 12, 2014 11:00AM to 12:00PM
Building 223, Room S105
The exploration of new states of matter resulting from reduced dimensionality and electron correlations has been at the forefront of condensed matter physics research. The overarching theme of my dissertation research is the emergent transport properties of several electronic materials such as strongly correlated electronic systems (EuB6 and manganites), 2D and 1D superconductors, and magnetically doped topological insulators. Hall effect measurements were performed on EuB6 single crystals and anisotropically strained thin films. The nonlinear features in the Hall resistivity are identified as signatures of magnetic field driven percolative phase transitions and electronic phase separation.

The transport measurements on low dimensional superconductors and topological insulators were carried out in a customized dilution refrigerator which hosts an assortment of in situ capabilities, such as film growth, sample rotation, electrical measurements, and quite uniquely, magnetic impurity deposition. Those in situ capabilities enabled a systematic study of the superconductor-insulator transitions in low dimensional superconducting systems, and led to the discovery of giant enhancement of superconductivity by a parallel magnetic field in ultrathin Pb films. The incremental in situ magnetic impurity deposition was employed for a systematic examination of the evolution of the spin-helical surface states of a 3D topological insulator in the presence of increasing spin-flip scattering.