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Raising the superconducting transition temperature in cuprates within a two-component scenario
Annette Bussmann-Holder 한국물리학회 2004 Current Applied Physics Vol.4 No.5
Two-component or two-channel superconductivity has been proposed since long to be a source of raising the superconducting transition temperatureTc considerably. The rst observation of two-component superconductivity was made in Nb-doped SrTiO3,yet without the hope forTc enhancement. An unambiguous observation of two superconducting gaps has been made in the recentlydiscovered high-Tc compound MgB 2 where the two component interband interaction ampliesTc by a factor of 1.6 as compared to asingle band system. Another candidate for such a scenario has been speculated to be veried in the cuprate superconductors, but theoverwhelming experimental evidence for a d-wave order parameter in the CuO2 planes has largely suppressed this aspect. Here it isshown that the coexistence of an s-wave and d-wave order parameter in cuprates is a scenario in which the observed highTcs can berealized. The crucial quantity is here the pairwise exchange interaction of holes between the two channels caused by quantuminterference. Lattice eects on superconductivity are explicitly incorporated and shown to be of major relevance to superconduc-tivity including various exotic isotope effects.
Elastic Anomalies Associated with the Antiferroelectric Phase Transitions of PbHfO3 Single Crystals
고재현,Krystian Roleder,Andrzej Majchrowski,Annette Bussmann-Holder 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.8
The temperature dependence of the elastic properties of antiferroelectric PbHfO3 was investigatedby using Brillouin scattering. The two structural phase transitions of antiferroelectricantiferroelectric-paraelectric phases were clearly identified from the discontinuous changes in theacoustic mode frequencies and the hypersonic damping. The substantial softening of the modefrequency, along with the remarkable increase in the acoustic damping observed in the paraelectricphase, indicated the formation of precursor noncentrosymmetric (polar) clusters and their couplingto the acoustic waves. This was corroborated by the observation of quasi-elastic central peaks,the intensity of which grew upon cooling toward the Curie point. The obtained relaxation timeexhibited a slowing-down behavior, suggesting that the dynamics of the precursor clusters becamemore sluggish on approaching the phase transition temperature.