S. Hoen

Elastic properties of single crystal Bi2Sr2CaCu2O8

Abstract We have measured the (in-plane) Youngs and (out-of-plane) shear moduli of superconducting crystals of Bi 2 Sr 2 CaCu 2 O 8 ( T c = 88 K ) as functions of temperature using “vibrating reed” techniques. No anomalous behavior is observed at any temperature (below room temperature), consistent with conventional thermodynamic behavior at T c and the absence of other structural phase transitions.

Magnetic and resistive determination of the oxygen isotope effect in La1.85Sr0.15CuO4

Abstract In polycrystalline samples of the superconducting oxide La1.85Sr0.15CuO4, the substantial substitution of 18O for 16O causes a small downward shift in the superconducting transition temperature Tc. Although Tc(onset) measured resistively differs by as much as two Kelvin from that measured magnetically, the two measurement methods yield comparable Tc shifts upon isotope substitution. Samples with different superconducting phases (as evidenced by resistive fine structure in the transition region) show similar isotope shifts for different phases. We determine an overall oxygen isotope shift in La1.85Sr0.15CuO4 corresponding to α = 0.140±.008, where Tc∼M−α and M is the oxygen mass.

Electron-phonon interactions in high-temperature oxide superconductors: Isotope effects and elasticity studies

Abstract The substitution of different oxygen isotopes into the high-T c oxide superconductors La 1.85 Sr 0.15 CuO 4 and YBa 2 Cu 3 O 7 is investigated by transport and magnetic measurements. For both materials, replacement of 16 O with 18 O depresses T c slightly. The observed shifts are much smaller than those expected from conventional electron-phonon pairing superconductivity. We also explore the elastic properties of La-, Y-, and Bi-based high-T c superconductors, including single crystals. Only La 1.85 Sr 0.15 CuO 4 shows a dramatic soft phonon mode above T c .

Anisotropic Transport in Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O

The anisotropic normal state transport properties of the superconducting oxides Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O are investigated by dc resistivity, thermoelectric power, high frequency conductivity, and uniaxial stress effects in single crystals. We also explore the superconducting state by measurements of Tc under c-axis stress, and oxygen isotope substitution. Energy gap structure is investigated by break junction single-crystal tunneling.

Magneto-elastic properties of NbSe3

Abstract The Youngs Modulus (Y) and internal friction (δ) have been measured in the charge density wave (CDW) conductor NbSe 3 . Anomalies are clearly resolved in Y and δ at the upper CDW transition, T 1 (144K) and in Y at the lower CDW transition, T 2 (59K). Below 100K, Y has been measured in transverse magnetic fields up to 8T. Small field-induced stiffening effects are observed.