99-10-21
ƒz[ƒ€ ã‚Ö 99-02-10 99-02-12 99-06-02 99-10-21 99-11-16

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u‰‰‘è–ÚF@Probing the Energy Gap of High Temperature Superconductors with Tunneling Spectroscopy: Evidence for Exotic Pairing

u@Žt@F@Prof. John Zasadzinski
@@@@@(Illinois Institute of Technology and Argonne National Laboratory)

“ú@Žž@F@•½¬11”N10ŒŽ21“ú (–Ø) 16:30-17:00
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—v@Ž|@F
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.


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 (011-706-3575Amoda@sci.hokudai.ac.jp)
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