Dong-Jin Jang

Superconducting energy gap in MgCNi3 single crystals: Point-contact spectroscopy and specific-heat measurements

Specific heat has been measured down to 600 mK and up to 8 T by highly sensitive ac microcalorimetry on MgCNi3 single crystals with Tc ≈ 7 K. Exponential decay of the electronic specific heat at low temperatures proved that a superconducting energy gap is fully open on the whole Fermi surface, in agreement with our previous magnetic penetration depth measurements on the same crystals. The specific-heat data analysis shows consistently the strong-coupling strength 2 /kBTc ≈ 4. This scenario is supported by the direct measurements of the gap via the point-contact spectroscopy. Moreover, the spectroscopy measurements show a decrease in the critical temperature at the sample surface, which accounts for the observed differences of the superfluid density deduced from the measurements by different techniques.

s-wave superconductivity probed by measuring magnetic penetration depth and lower critical field of MgCNi

The magnetic penetration depth

_{3}

\ensuremath{\lambda}

single crystals

has been measured in

Nodeless superconductivity in the infinite-layer electron-doped cuprate superconductor Sr0.9La0.1CuO2

{\text{MgCNi}}_{3}

Evidence of conventional superconductivity in single-crystalline MgCNi3

single crystals using both a high-precision tunnel diode oscillator (TDO) technique and Hall probe magnetization (HPM). In striking contrast to previous measurements in powders,

Comparative study of the pressure effects on the magnetic penetration depth in electron- and hole-doped cuprate superconductors

\ensuremath{\delta}\ensuremath{\lambda}(\text{T})

Finite gap behaviour in the superconductivity of the ‘infinite layer’ n-doped high-Tc superconductor Sr0.9La0.1CuO2

deduced from TDO measurements increases exponentially at low temperature, clearly showing that the superconducting gap is fully open over the whole Fermi surface. An absolute value at zero temperature

Angular dependences of the motion of the anisotropic flux line lattice and the peak effect in MgB2

\ensuremath{\lambda}(0)=230\text{ }\text{nm}

TWO-LEVEL RANDOM TELEGRAPH NOISE FROM MOVING VORTICES IN CLEAN MgB2 SINGLE CRYSTAL

is found from the lower critical field measured by HPM. We also discuss the observed difference of the superfluid density deduced from both techniques. A possible explanation could be due to a systematic decrease in the critical temperature at the sample surface.