题目：Scattering and pairing in a shallow Fermi sea

报告人：Kamran Behnia       cole Supérieure de Physique et de Chimie Industrielles (ESPCI)

地点： 教十二-423

时间：5月26，周四，16:00-17:00

Abstract:

Doping a semiconductor will eventually lead to the emergence of a metallic ground state.  Strontium titanate (SrTiO3) becomes a metal, upon infinitesimal doping, thanks to its long Bohr radius. The extremely mobile carriers of a shallow Fermi sea over a seafloor carved by distant dopants present several mysteries. The first is the occurrence of superconductivity in spite of the tiny Fermi energy, thirty times lower than the Debye energy [1].

The second is the persistence of T2 resistivity due to electron-electron scattering.  The T2 behavior in SrTiO3 can be tuned over four orders of magnitude and persists in the single-band dilute limit despite the absence of two known mechanisms for T2 behavior, distinct electron reservoirs and Umklapp processes [2].

More recently, we have found that in Ca-doped and oxygen-reduced SrTiO3, suffers both a ferroelectric and a superconducting transition in a narrow range of doping. This happens when the concentration of mobile electrons is too low to screen the localized electric dipoles. This is the first solid in which these two instabilities, hitherto believed to be mutually exclusive, coexist with each other.

（1）X. Lin, Z. Zhu, B. Fauqué  and K. Behnia, Phys. Rev. X 3,        021002 (2013).

 （2）X. Lin, B. Fauqué and K. Behnia, Science 349, 945 (2015).

 （3）C. W. Rischau et al., to be published.

个人简介：

Kamran Behnia obtained his Ph.D. working on heavy-fermion systems in Grenoble. He then spent two years as a postdoctoral fellow at University of Geneva. In 1992, he was employed by Centre National de la Recherche Scientifique (CNRS) and spent seven years working on organic and cuprate superconductors at Paris-Sud University. Since 2000, he has been based at Ecole Supérieure de Physique et de Chimie Industrielles (ESPCI) in Paris. He is interested in collective quantum phenomena in a variety of solids ranging from semimetals to superconductors. His book Fundamentals of Thermoelectricity was recently published by Oxford University Press.

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