講演題目：　Realization of the FFLO state in CeCoIn5 at ambient pressure:
                 a simple lesson about extreme conditions’ research

講　師　：　Stan Tozer  (The National High Magnetic Field Laboratory
                                                      Tallahassee, Florida, U.S.A.)

日　時　：　平成15年7月8日（火）　14:00-15:00
場　所　：　北海道大学大学院理学研究科物理学専攻　大学院講義室
　　　　　　　理学部　2号館（2−11号室）

要　旨　：
　 　A brief introduction to recent high pressure transport and magnetization experiments in pulsed and dc magnetic fields and some promising initial results will be followed by a presentation of our ambient pressure studies of the FFLO state recently found in CeCoIn5. This phase was first predicted in 1964 by Fulde & Ferrell and, independently, Larkin & Ovchinnikov. They showed that, in the paramagnetic limit, an applied magnetic field H coupling to the individual electron spins of superconducting Cooper pairs could induce a phase transition from a uniform to a novel, spatially varying superconducting phase. Buzdin and Brison predicted in 1996 that, within this FFLO phase, solutions corresponding to higher Landau level states of the order parameter should occur. I will present heat capacity measurements on the layered structure heavy fermion superconductor CeCoIn5 revealing a phase transition within the standard BCS superconducting state at high field
and low temperature for fields parallel to the layers. Within this wedge
of phase space, our magnetization measurements display a cascade of first order phase transitions. The observation of steps in the magnetization is a result of orbital quantization of the order parameter and, with the heat capacity measurements, provides the first direct evidence of the existence of the FFLO phase. The work presented is the result of an extensive collaboration funded by an NHMFL In-house research proposal, the State of Florida, the Department of Energy, and the National Science Foundation. 
  I would like to acknowledge my colleagues H.A. Radovan, T.P. Murphy, S.T. Hannahs, E.C. Palm, N.A. Fortune, C. Agosta, I. Mihut, C. Catalin, D. Hall, J. Singleton, and A. Bangura.

世話人　　　網塚　浩 （北海道大学大学院理学研究科）
　　　　　　　　　　　　（Tel: 011-706-3484, amiami@phys.sci.hokudai.ac.jp）