Pseudo Gap Formation Studied by B_<2u> Phonon Measurements

概要

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Netrtron scattering sttrdies on a c-axis polarized B3., phonon have been carried otrt by usingsingle crystals 0['YB.llL2CL13O7, YBaxCtraOce.w and YBaxCtrx.oZno.uOc;.ws. For YBaxCueOw, sharpdecreases in the energy and xvidth of' the phonon aaaode have been observed with decreasingLexnperatt+re T at arotrnd the strpercondttcting transition tetaaperattrre T.. For the trnderdopedsanaples, the gradttal downxvard deviations of these qtrantities frorn the ordinary T-dependencebegin f'ar above T. with decreasing T, which is considered to be associated with the formation ofthe pseudo gap with tlae sanae syraauaaetry as that of the svrpercondtrcting order parameter, i.e., the(r'-y')-like one. These deviations beconae significant, with decreasing T, at tenaperattrres higherthstn tlae so-called spin-gap teratperattzre ISG of YBazCu3O.5.7 ('='15O K). Observed insensitivenattnre of the anornaly ?rbove T. to tlae Zn-doping can be explained by considering the wavevector ((7) dependence of the psetrdo gap and the cotrpling strength of the B2., naode to the gap,and also Icy cozasidering thsrt randorauness effects introdtzced by the doping are 11101'[1) significantin the q-region with the staa?t1ler energy gap.
社団法人日本物理学会の論文
1998-09-15