Rapid thermoelectric power drop to zero at 250K in superconducting Hg-compounds

Abstract We report for the first time that the thermoelectric power (TEP), S(T), drops to zero very rapidly around T c,uso = 250K in the superconducting Hg-compounds. The sign of TEP is negative and the room temperature value is small, S(RT) = −2 μ V/K. The temperature dependence of resistance of the same sample measured with the applied current I = 10 μ A, shows a step-like drop at T c,uso =250K becoming zero resistance around T=120K. At T=230K which is the temperature below the step-like resistance drop, we measured the I-V characteristics of the sample. For the applied current lower than 1.8μA, the measured resistance is zero initially and it gradually becomes finite in time. It takes approximately 30 seconds before it saturates to a stable value. For 1 > 1.8 μ A, the resistance becomes finite immediately after we turn on the current source, i.e., there is no time lagging response in voltage probe. The I-V characteristic is Ohmic for 1.8 μ A μ A. Since the TEP is a zero current transport coefficient, the observed rapid drop of TEP around 250K together with the initial zero resistance behavior for T μ A, may indicate an intrinsic superconducting transition at T c,uso =250K of the multi-phase Hg-compounds.