Intrinsic resistance fluctuations in mesoscopic superconducting wires

Abstract

The puzzling appearance of a large resistance peak in the superconducting state near T, of mesoscopic superconducting wires is analyzed. It is shown that this resistance anomaly can be explained in terms of thermal Buctuations producing phase slips of the superconducting order parameter in quasi-one-dimensional wires. Good quantitative agreement with the experimental observations is obtained within the framework of the modified Langer-Ambegaokar and McCumber-Halperin models.A typical resistive transition into the superconducting state, R(T), is usually described as a slow but monotonic decrease of the resistance due to fluctuations of the superconducting order parameter alt above T" followed by a sharp drop at the transition temperature T = T,. Recent experiments on mesoscopi c superconducting samples revealed, however, a surprising R(T) behavior characterized by the presence of an anomalous resistance peak in the vicinity of T,. 2 The measured resistance typically becomes 10 to 20% higher than the normal-state resistance value B"which is extracted &om the plateau in the R(T) curve above T,. In an attempt to understand the origin of this phenomenon, Santhanam et al. , as well as Vloeberghs et oL, suggested several physical mechanisms based on the ideas discussed in Refs. 3 -5 which, however, failed to explain quantitatively the experimental observations.In this paper we show that the anomalous resistance peak in mesoscopic superconducting samples, with a width m much smaller than the temperature-dependent coherence length ((T) and the charge imbalance relaxation length Aq(T), s is related to intrinsic resistive Huctuations which can be analyzed within the framework of the Langer-Ambegaokar (LA) and McCumber-Halperins (MH) models. These models have to be modified to take into account the confinement of the superconducting current by the extremely narrow lines forming a mesoscopic sample.Typical experimental zero-field R(T) curves, clearly showing a resistance peak above T"are plotted for different transport currents I in Fig. 1. These data were obtained on a 1 x 1 pm2 square mesoscopic Al loop having a thickness t = 25 nm and a width m = 0.15 pm (see Fig. 1 inset). The details of the sample preparation and characterization have been described in detail elsewhere. ' Different samples all have a sheet resistance ranging between 1.5 and 2.0 0/U at 4.2 K, indicating a well-defined metallic character. These values are nearly 4 orders of magnitude smaller than the typical sheet resistance R~h/4e 6.45 kQ/CI for which electron localization phenomena become important.Therefore, the existence of the anomalous R(T) peak above T, ( Fig. 1) cannot be related to a resistance increase due to a pronounced granularity or disorder-induced effects.

Metal–Bosonic Insulator–Superconductor Transition in Boron-Doped Granular Diamond

“…With the discovery of quasi-2D cuprates, the RðTÞ peak around T c was also reported for these lowdimensional materials, such as NdCeCuO [7], BiSrCaCuO [8,9], and LaSrCuO [10,11], with the peak amplitude reaching 400%-700%. In 2D and 1D microstructures [6,[12][13][14][15][16], made from conventional superconducting materials (mostly Al), a narrow resistance peak close to T c was also observed, with the peak amplitude reaching the 400% level.Different models were used to explain the nature of the anomalous RðTÞ peak: normal-metal-superconductor boundaries, disorder and fluctuations, vortex dynamics and Josephson coupling in layered systems, charge imbalance, and competition between superconducting and insulating states in 2D systems [1,2,4,6,8,[12][13][14]16,17].All these observations of the RðTÞ peak around T c and the corresponding models and theories, formulated to explain the corresponding experimental data, are very much linked to the reduced dimensionality of the investigated systems: 2D or/and 1D. We have found reports on the RðTÞ peak for 3D-like metallic Cu-Zr glasses only in a couple of previous publications [17,18] with a quite small RðTÞ peak amplitude-less than 3%.…”

“…With the discovery of quasi-2D cuprates, the RðTÞ peak around T c was also reported for these lowdimensional materials, such as NdCeCuO [7], BiSrCaCuO [8,9], and LaSrCuO [10,11], with the peak amplitude reaching 400%-700%. In 2D and 1D microstructures [6,[12][13][14][15][16], made from conventional superconducting materials (mostly Al), a narrow resistance peak close to T c was also observed, with the peak amplitude reaching the 400% level.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]), the two characteristic temperatures T c (local) and T c (global) are different: T c (global) <T c (local). Localized bosonic islands are formed first at higher temperature T c (local), which leads to the suppression of conductivity N !…”

“…Different models were used to explain the nature of the anomalous RðTÞ peak: normal-metal-superconductor boundaries, disorder and fluctuations, vortex dynamics and Josephson coupling in layered systems, charge imbalance, and competition between superconducting and insulating states in 2D systems [1,2,4,6,8,[12][13][14]16,17].…”

Assembling the puzzle of superconducting elements: a review

“…Aluminum superconducts below 1.18 K [62], and when in mesoscopic wire form shows a peculiar resistance peak in the superconducting state near T c , attributed to thermal fluctuations producing phase slips of the superconducting order parameter [68].…”