Browsing by Author "Su, T. H."

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Evidence for s-wave superconductivity in noncentrosymmetric Re(24)Nb(5) from (93)Nb NMR measurements
(2011-08-25)
Lue, C. S.
;
Su, T. H.
;
Liu, H. F.
;
Young, Ben-Li
;
電子物理學系
We report a (93)Nb nuclear magnetic resonance (NMR) study on the noncentrosymmetric superconductor Re(24)Nb(5). Below the superconducting temperature T(c)(H), the spin susceptibility probed by the (93)Nb NMR Knight shift gradually decreases with lowering temperature, accompanied by the broadening of the resonance spectrum. Such behavior is commonly observed in the BCS-type superconductors. The (93)Nb NMR spin-lattice relaxation rate (1/T(1)) shows a well-defined coherence peak just below T(c)(H), followed by a marked decrease with further decreasing temperature. Moreover, the 1/T(1) data in the superconducting state were found to obey a single exponential expression, yielding a nodeless gap Delta/kB = 10.3 K. This value gives the ratio of 2 Delta/kBT(c)(H) = 3.55, that is almost identical with the value of 3.5 predicted from BCS theory. On these bases, we conclude that the noncentrosymmetric Re(24)Nb(5) compound can be characterized as a weakly coupled BCS-type superconductor.
Evidence for s-wave superconductivity in noncentrosymmetric Re24Nb5 from Nb-93 NMR measurements
(2011-08-25)
Lue, C. S.
;
Su, T. H.
;
Liu, H. F.
;
Young, Ben-Li
;
電子物理學系
We report a Nb-93 nuclear magnetic resonance (NMR) study on the noncentrosymmetric superconductor Re24Nb5. Below the superconducting temperature T-c(H), the spin susceptibility probed by the Nb-93 NMR Knight shift gradually decreases with lowering temperature, accompanied by the broadening of the resonance spectrum. Such behavior is commonly observed in the BCS-type superconductors. The Nb-93 NMR spin-lattice relaxation rate (1/T-1) shows a well-defined coherence peak just below T-c(H), followed by a marked decrease with further decreasing temperature. Moreover, the 1/T-1 data in the superconducting state were found to obey a single exponential expression, yielding a nodeless gap Delta/kB = 10.3 K. This value gives the ratio of 2 Delta/kBT(c)(H) = 3.55, that is almost identical with the value of 3.5 predicted from BCS theory. On these bases, we conclude that the noncentrosymmetric Re24Nb5 compound can be characterized as a weakly coupled BCS-type superconductor.
NMR evidence for the partially gapped state in CeOs(2)Al(10)
(2010-11-22)
Lue, C. S.
;
Yang, S. H.
;
Su, T. H.
;
Young, Ben-Li
;
電子物理學系
We report the results of a (27)Al nuclear magnetic resonance (NMR) study of CeOs(2)Al(10) at temperatures between 4 and 300 K. This material has been of current interest due to indications of hybridization gap behavior below the transition temperature T(o)similar or equal to 29 K. Five (27)Al NMR resonance lines that are associated with five nonequivalent crystallographic aluminum sites have been resolved. For each individual aluminum site, the low-temperature NMR Knight shift goes over a thermally activated response. The temperature-dependent spin-lattice-relaxation rate exhibits a rapid drop below T(o), indicative of the formation of an energy gap in this material. We interpret the Knight shift and the relaxation-rate data in light of the presence of a pseudogap with residual electronic density of states at the Fermi level. Moreover, the magnitude of the pseudogap of 120 K is extracted from NMR results, in agreement with the value obtained from the inelastic neutron-scattering experiment.
NMR evidence for the partially gapped state in CeOs2Al10
(2010-11-22)
Lue, C. S.
;
Yang, S. H.
;
Su, T. H.
;
Young, Ben-Li
;
電子物理學系
We report the results of a Al-27 nuclear magnetic resonance (NMR) study of CeOs2Al10 at temperatures between 4 and 300 K. This material has been of current interest due to indications of hybridization gap behavior below the transition temperature T-o similar or equal to 29 K. Five Al-27 NMR resonance lines that are associated with five nonequivalent crystallographic aluminum sites have been resolved. For each individual aluminum site, the low-temperature NMR Knight shift goes over a thermally activated response. The temperature-dependent spin-lattice-relaxation rate exhibits a rapid drop below T-o, indicative of the formation of an energy gap in this material. We interpret the Knight shift and the relaxation-rate data in light of the presence of a pseudogap with residual electronic density of states at the Fermi level. Moreover, the magnitude of the pseudogap of 120 K is extracted from NMR results, in agreement with the value obtained from the inelastic neutron-scattering experiment.