1209.2965 (Wei Liu et al.)

AC evidence of a field tuned 2D superconductor-metal transition in a
low-disorder InO$_x$ film    [PDF]

Wei Liu, LiDong Pan, Jiajia Wen, Minsoo Kim, G. Sambandamurthy, N. P. Armitage

Employing microwave spectroscopy, we investigated the field tuned quantum phase transition between the superconducting and the resistive states in a low-disorder amorphous InO$_x$ film in the frequency range of 0.05 to 16 GHz. Our AC measurements are explicitly sensitive to the critical slowing down of the characteristic frequency scales approaching a transition. The relevant frequency scale of superconducting fluctuations approaches zero at a field $B_{sm}$ far below the field $B_{cross}$ where different isotherms of resistance as a function of magnetic field cross each other. The phase stiffness at the lowest frequency vanishes from the superconducting side at B $\approx B_{sm}$, while the high frequency limit extrapolates to zero near $B_{cross}$. Our data are consistent with a scenario where $B_{sm}$ is the true quantum critical point for a transition from a superconductor to an anomalous metal, while $B_{cross}$ only signifies a crossover to a regime where superconducting correlations make a vanishing contribution to both AC and DC transport measurements in the low-disorder limit.

View original: http://arxiv.org/abs/1209.2965