Effect of external electromagnetic radiation on the anomalous metallic behavior in superconducting Ta thin films

Abstract

We investigated transport characteristics of superconducting Ta thin films with three configurations in rf radiation filters; no filter, only room-temperature filters, and low-temperature filters in addition to room-temperature filters. The transport properties near the transition temperature are strongly dependent on whether the room-temperature filter is installed or not. The entire transition is shifted to higher temperature with loading layers of the room-temperature filters. Once the zero-resistance state is achieved at B=0, no strong radiation effect is observed even with low-temperature filters installed.When magnetic field is turned on, the nonzero-resistance saturation at low temperatures is revealed without low-temperature filters, which has been considered to be magnetic-field-induced quantum metallic phase. However, the insertion of the additional low-temperature filter weakens the saturation of the resistance, the signature of the metallic behavior. This observation suggests that the previously reported anomalous metallic state in Ta films is mainly induced by the unfiltered radiation and, thus, the intrinsic metallic ground state should be limited to the narrow range of magnetic fields near the critical point, if exists.

Quantum phase transitions in two-dimensional superconductors: a review on recent experimental progress

“…However, after installing the external lowpass filters, the resistance follows the activated behavior down to ultralow temperatures and the resistance saturation behavior disappears (the blue curves), indicating that the metallic behavior could be eliminated by adequately filtering the external noise [164]. The so-called 'anomalous metal state' induced by the external electromagnetic radiation was also reported in superconducting Ta thin films [165].…”

Low-frequency electrodynamics in the mixed state of superconducting NbN and a-MoGe films using two-coil mutual inductance technique

“…For U 0 and α L we use the phenomenological temperature variations in equations ( 9) and (10) with the additional smearing factor discussed in section 2: T0 , where t = T Tc(H) is the scaled temperature. For η we use the phenomenological temperature variation in equation (11), η ∼ η 0 ( 1−t 2 1+t 2 ). We treat U 0 and T 0 as adjustable parameters and fix α L0 and η 0 in such a way that their values at 2 K are as close as possible to the values extracted from the GR model.…”

“…In recent years, there has been a renewed interest in the study of superconducting thin films owing to their technological applications. Compared to bulk superconductors, the 2D vortex lattice in thin films is much more fragile and susceptible to perturbations [8][9][10][11]. Consequently, thermal [12,13] and quantum [14,15] fluctuations can play a much more dominant role in these systems.…”