However, this mechanism would lead to R e-ph∝T for T>Λ D and R e-ph∝T 5 for T≪Λ D[26], neither of which is consistent with the observed temperature dependence. (Here R e-ph is the resistance due to the electron-phonon scattering, and Λ D is the Debye temperature.) Considering

the exponent a to be slightly smaller than 2, we attribute its origin to the electron-electron scattering. In a 2D Fermi liquid, it leads to a resistivity R e−e with the following form [27], (4) where C ′ is a proportional constant, ε F is the Fermi energy, and k B is the Boltzmann constant. The log term in Equation 4 results in a weaker temperature dependence than that in a 3D Fermi liquid (∝T 2). Fitting the data with Equation 4 instead Tipifarnib cell line of the C T a term in Equation 1 gives ε F≈0.1 eV, although the uncertainty is quite large. We note that a decrease in resistance in a conventional metal film is usually Selleckchem 17-AAG very small in this temperature range. For example, it is less than 1% within the range of 2

R □ between 20 and 5 K in our samples, Δ R □, amounts to as much as 5% to 15% of R n,res (see Figure 2 and Table 1). In this sense, the observed temperature dependence is rather unusual. The ( )-In surface

studied here has an atomic-scale dimension in the normal direction and may thus have an enhanced electron-electron interaction because of insufficient electrostatic screening. In comparison, the contribution from the electron-phonon interaction can be smaller because it decreases rapidly at low temperatures as R e-ph∝T 5. Residual resistance in the superconducting phase below T c The superconducting fluctuation theories state that R □ becomes exactly zero at T c , as indicated by Equation 2. However, a close inspection into the magnified plots (Figure 3a) reveals that R □ has a finite tail below T c . To examine whether R □ becomes zero at sufficiently low temperatures, we have taken the current-voltage Megestrol Acetate (I-V) characteristics of sample S1 below T c down to the lowest temperature of 1.8 K. Figure 3b displays the data in the log-log plot form. Although the I-V characteristics exhibit strong nonlinearity at the high-bias current region, they show linear relations around the zero bias at all temperatures. The sheet resistances R □ determined from the linear region of the I-V curves are plotted in Figure 3c as red dots. R □ decreases rapidly as temperature decreases from T c , but it becomes saturated at approximately 2×10−2 Ω below 2 K. Figure 3 Residual resistance in the superconducting phase below T c . (a) Magnified view of Figure 2 around T c .