物理系seminar：Superconductivity of heavy fermions: The quest for coupling mechanism

報告題目： Superconductivity of heavy fermions: The quest for coupling mechanism 報告人： Prof. Frank Steglich Max Planck Institute for Chemical Physics of Solids, Dresden, Germany 報告時間： 2013-11-28 16:00 報告地點：鄭裕彤大講堂摘要： I shall first address the early discovery of unconventional superconductivity in the heavy-fermion (HF) metal CeCu2Si2. Then two fundamentally different antiferromagnetic quantum-critical-point (QCP) scenarios proposed for HF metals will be briefly discussed. CeCu2Si2 turns out to be the prototype of a conventional quantum critical material. Here, a three-dimensional spin-density-wave (SDW) QCP exists, and almost quantum-critical spin fluctuations are driving the formation of Cooper pairs.
An unconventional antiferromagnetic QCP, frequently called a 4f-orbital-selective Mott transition, at which the Kondo effect becomes destroyed, has been identified in a small number of HF systems, e.g., CeCu6-xAux [7] and YbRh2Si2. In both compounds, no superconductivity exists at T > 10 mK. However, HF superconductivity with maximum Tc ≈ 2.3 K develops in the vicinity of the pressure-induced Kondo-destroying QCP (pc ≈ 2.3 GPa) for CeRhIn5. Future research activities will have to unravel the potential differences between HFSC, driven by SDW fluctuations, and HFSC that forms in the vicinity of an orbital-selective Mott transition. 個人簡介： Prof. Dr. Frank Steglich is a famous German physicist. He received the Gottfried Wilhelm Leibniz Prize by the Deutsche Forschungsgemeinschaft (German Research Foundation) in 1986 and a number of other recognitions. He is the founding director of the Max Planck Institute for Chemical Physics of Solids in Dresden, Germany and is currently also Vice President of the Deutsche Forschungsgemeinschaft.
Frank Steglich discovered the first heavy fermion superconductor, CeCu2Si2, while working as a postdoctoral student in Cologne, Germany in 1978. CeCu2Si2 is the first metallic system to be discovered in which the superconductivity is driven by electron-electron interactions, rather than the electron-phonon interaction that is responsible for conventional BCS superconductivity. The discovery of this material revolutionized research into superconductivity, establishing the reality of electronically mediated superconductivity and foreshadowing the discovery of a wide range of heavy electron superconductors, and the subsequent discovery of electronically mediated pairing in cuprate high temperature superconductors. The first published report of the phenomenon occurred in 1979, by which time Steglich had taken up a junior faculty position at the University of Darmstadt, and confirmed the existence of bulk superconductivity through the measurement of the specific heat anomaly at the transition temperature of Tc=0.5K.