Phase diagram of a current-carrying superconducting film in the absence of a magnetic field

Abstract

We present the phase diagram for the current states of superconducting films, based on the experimental investigation of the resistive transition induced by transport current. We found that a rather narrow film with the width w < 5λ ⊥ (T ) (λ ⊥ is the penetration depth of the magnetic field) never enters the vortex state, but experiences direct transition from the purely superconducting state to the resistive state with phase-slip centers as soon as the current exceeds the Ginzburg-Landau critical current I GL c . The Meissner current state of the films of intermediate width, 5λ ⊥ < w < 10λ ⊥ , transforms at I > 0.8I GL c to the vortex resistive state which exists within the current interval 0.8I GL c < I < I m , where the value I m of the upper critical current is in a good agreement with the theory. The vortex state of wide films, w > 10λ ⊥ , is realized within the current region I AL c < I < I m , where I AL c is the transition point to the vortex state calculated for the limiting case w ≫ λ ⊥ . At I > I m , the films with the width w > 5λ ⊥ (T ) enter a vortex-free resistive state with phase-slip lines. PACS numbers: 74.40+k According to the Ginzburg-Landau (GL) theory [1], if the transport current through a narrow superconducting film (superconducting channel) exceeds the depairing current,the superconducting state of the channel is destroyed and transforms to the normal state, as shown in Fig.1. In (1), Φ 0 is the magnetic flux quantum, w is the film width, λ ⊥ (0) = 2λ 2 (0)/d is the penetration depth of the magnetic field into the superconducting film, ξ (0) and λ (0) are the coherence and London lengths, respectively, at zero temperature, and d is the film thickness. Later it was found that the real scenario of the resistive phase transition of the superconducting channel is more complex. Namely, as the transport current exceeds 0 1 0 1 I c V/V n R n V/V n I/I c FIG. 1: Current-voltage characteristic (IVC) of a narrow superconducting channel according to the GL theory. Here R n is the channel resistance in the normal state, and V n is the voltage jump at the point of the resistive transition. * e-mail: zolochevskii@ilt.kharkov.ua 0 100 200 300 0 200 400 600 I c V, µV I, µA FIG. 2: Typical IVC of a superconducting film channel Sn4 at the temperature T /T c = 0.98.I GL c , an inhomogeneous resistive state appears in the channel, consisting of alternating superconducting and quasi-normal regions [2]; the latter are the specific dynamic formations known as phase-slip centers (PSCs). The number of PSCs increases with the transport current, and at I > I cn ≫ I GL c the resistive state turns to the completely normal state. The basic feature of the current-voltage characteristics (IVCs) of superconducting channels in the resistive state are regular voltage steps (Fig. 2), which were first observed in tin whiskers [3,4] and in narrow tin films [5]. We note the following important peculiarities of the step-like IVCs: the multiplicity of differential resistances of the sloping IVC parts, the intersection of the ...

Effect of meter-range electromagnetic irradiation on the current-voltage characteristics of wide superconducting films

“…The films were fabricated according to the original technology [3], which ensures high quality of the film side edges and a uniform thickness. This has been confirmed by good agreement of the experimentally measured values and temperature dependences of their critical currents [3,4] with the results of the Aslamazov-Lempitzky theory [5,6] for the defect-free films. The films were deposited on the substrates of optically polished monocrystalline quartz, which ensures an efficient heat removal [7] and the absence of overheating.…”

Resistive current state of a wide superconducting film

“…In this connection it is worth to mention the theoretical work 6 which we have already previously discussed. 7 Here it is important to note that the vortex picture of resistivity in Ref. 6 agrees with analytical calculations.…”

Review of superconducting transition-edge sensors for x-ray and gamma-ray spectroscopy

“…Between steps, the differential resistance is an integer multiple of the resistance after the first jump. This behavior has been shown in numerous experiments [135][136][137][138], to result from phase-slips, where the phase of the superconducting order parameter is increasing at different rates on the two sides of a spatially localized region.…”