"Probing the Energy Gap of High Temperature Superconductors with Tunneling Spectroscopy: Evidence for Exotic Pairing"
Prof. John Zasadzinski

講演題目：　Probing the Energy Gap of High Temperature Superconductors with Tunneling Spectroscopy: Evidence for Exotic Pairing
講　師　：　Prof. John Zasadzinski
　　　　　(Illinois Institute of Technology and Argonne National Laboratory)
日　時　：　平成11年10月21日 (木) 16:30-17:00
場　所　：　北海道大学理学部２号館大学院講義室（2-2-11）

要　旨　：
TTunneling spectroscopy is presented for a variety of high temperature　superconducting cuprates. The data for electron doped compounds such as　Nd-Ce-Cu-O which have a relatively low Tc = 22K are consistent with an　s-wave energy gap and ordinary phonon mediated pairing. However, the　tunneling data for hole-doped cuprates such as Bi-Sr-Ca-Cu-O (Bi2212) with　an optimal Tc = 95 K are more consistent with a d-wave energy gap. The　doping dependence of the energy gap parameter in Bi2212 is anomalous,　increasing to very large values in the underdoped regime even as Tc　decreases. This gap parameter follows the trend of the antiferromagnetic　exchange energy, J, which indicates that the pairing is of magnetic origin.　 The high bias tunneling spectra reveal a dip feature that is often quite　pronounced and may be related to the resonance peak in the magnetic　excitations probed by neutron scattering. Also, the high bias features　include a secondary peak which might be an indication of a competing　pseudogap of magnetic origin.

小田研　（北海道大学大学院理学研究科）
（moda@sci.hokudai.ac.jp）

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