Berezinskii-Kosterlitz-Thouless transition and fluctuation paraconductivity in Y1Ba2Cu3O7 single crystal films

Gasparov, V. A.

doi:10.1016/0921-4534(91)90097-i

Cited by 33 publications

(10 citation statements)

References 27 publications

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“…The emergence of 2D superconductivity in the thicker FST films suggests its intrinsic nature for FST films. It should be mentioned that 2D superconductivity has also been reported in single crystals and thick films of high T c superconductors, such as 500 nm thick FeSe films25, single crystals of cuprates3839 and 500 nm thick cuprate films40. The 2D superconductivity in these systems can be understood by considering their layered structures and the weak interplane coupling since the coherence lengths perpendicular to the planes are very short25383940.…”

Section: Discussionmentioning

confidence: 97%

Quasi-two-dimensional superconductivity in FeSe0.3Te0.7 thin films and electric-field modulation of superconducting transition

Zhu

Mei

Wei

et al. 2015

Sci Rep

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We report the structural and superconducting properties of FeSe0.3Te0.7 (FST) thin films with different thicknesses grown on ferroelectric Pb(Mg1/3Nb2/3)0.7Ti0.3O3 substrates. It was shown that the FST films undergo biaxial tensile strains which are fully relaxed for films with thicknesses above 200 nm. Electrical transport measurements reveal that the ultrathin films exhibit an insulating behavior and superconductivity appears for thicker films with Tc saturated above 200 nm. The current-voltage curves around the superconducting transition follow the Berezinskii-Kosterlitz-Thouless (BKT) transition behavior and the resistance-temperature curves can be described by the Halperin–Nelson relation, revealing quasi-two-dimensional phase fluctuation in FST thin films. The Ginzburg number decreases with increasing film thickness indicating the decrease of the strength of thermal fluctuations. Upon applying electric field to the heterostructure, Tc of FST thin film increases due to the reduction of the tensile strain in FST. This work sheds light on the superconductivity, strain effect as well as electric-field modulation of superconductivity in FST films.

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Section: Discussionmentioning

confidence: 97%

Quasi-two-dimensional superconductivity in FeSe0.3Te0.7 thin films and electric-field modulation of superconducting transition

Zhu

Mei

Wei

et al. 2015

Sci Rep

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“…In the time-intervals, when the inequality (14) holds, the electric field is zero to an accuracy of a (see (13)). Now one can easily obtain the expression for the surface impedance in an explicit form.…”

Section: Calculation Of the Surface Impedancementioning

confidence: 98%

“…The size effect was observed not only at bilateral (see, for example, Refs. [12,13,9]), but also at unilateral excitation [14][15][16]. At unilateral excitation it manifests itself as an abrupt growth of the surface resistance of the plate and, consequently, as a drastic increase in the ac absorption at H > H p .…”

Section: Introductionmentioning

confidence: 99%

Nonlinear Interaction of the Electromagnetic Waves Irradiating the Plate of a Hard Superconductor From the Opposite Sides

Derev’anko

Lyubimova

Lyubimov

et al. 2000

Magnetic and Superconducting Materials

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It is well-known that the size effect occurs in a conducting plate if the penetration depth of the electromagnetic wave irradiating the sample is of the same order as the plate thickness. At unilateral excitation, the size effect manifests itself as an abrupt growth of the surface resistance of the plate. It takes place due to the drastic increase of the electric field inside the sample under the condition of its full transparency. The electric field becomes of the same order as the magnetic field, and the surface resistance of the sample increases correspondingly. In the present paper we show that even at small amplitudes Hi of an incident wave (which we call the "base" wave with a frequency of ui) as it cannot penetrate through the whole volume of a hard superconductor, one can, nevertheless, observe the size effect by means of another wave (the "assisting" wave with an amplitude Hi and a frequency of 012), propagating in the opposite direction. This effect stems from the nonlinearity of superconducting media and does not depend essentially on the peculiarities of the nonlinearity mechanism. When the penetration regions of both waves overlap, the nonlinearity results in the appearance of all combined harmonics of the waves at every point of the sample. In particular, there exists a signal on the first harmonics u>\. As a result, the surface resistance on the frequency w\ of the base wave being small without the assisting wave, increases drastically when the penetration regions overlap each other. In the present paper we have studied the dependence of the surface impedance on the first frequency u>\ vs the amplitude #2 of the second wave. All the calculations in this paper were performed within the framework of the critical state model. The described effect of the stimulated transparency of the superconducting plate when acted upon by the assisting wave was observed experimentally.

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“…[26]. This technique was extensively used for the study of the λ(T) dependence for YBCO, ZrB 12 , and MgB 2 single crystals and thin films [31,32].…”

Section: Methodsmentioning

confidence: 99%

Complex conductance of ultrathin La2–xSrxCuO4 films and heterostructures

Gasparov

Božović

2015

Low Temperature Physics

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We used atomic-layer molecular beam epitaxy to synthesize bilayers of a cuprate metal (La 1.55 Sr 0.45 CuO 4 ) and a cuprate insulator (La 2 CuO 4 ), in which each layer is just one unit cells thick. We have studied the magnetic field and temperature dependence of the complex sheet conductance, σ(ω), of these films. Experiments have been carried out at frequencies between 2-50 MHz using the single-spiral coil technique. We found that: (i) the inductive response starts at ∆T = 3 K lower temperatures than Re σ(T), which in turn is characterized by a peak close to the transition, (ii) this shift is almost constant with magnetic field up to 14 mT; (iii) ∆T increases sharply up to 4 K at larger fields and becomes constant up to 8 T; (iv) the vortex diffusion constant D(T) is not linear with T at low temperatures as in the case of free vortices, but is rather exponential due to pinning of vortex cores, and (v) the dynamic Berezinski-Kosterlitz-Thouless (BKT) transition temperature occurs at the point where Y = (l ω /ξ + ) 2 = 1. Our experimental results can be described well by the extended dynamic theory of the BKT transition and dynamics of bound vortex-antivortex pairs with short separation lengths. Ultrathin films of high-temperature superconductors have been studied intensely, with numerous attempts to observe the Berezinski-Kosterlitz-Thouless (BKT) transition [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. For example, a few unit-cell (UC) thick YBa 2 Cu 3 O 7-x (YBCO) films sandwiched between semiconducting or insulating layers have broader resistive transitions than thicker ones, which have been attributed to the BKT physics [4][5][6]. The same explanation was proposed for the observation of nonlinear current-versus-voltage (I-V) characteristics in YBCO, BiSrCaCuO, and TlBaCaCuO single crystals and thin films (see Ref. 7 and references therein). This has been a matter of substantial debate, though. For example, Repaci et al. [8] found the I-V characteristics to be ohmic even in 1 UC thick YBCO films at temperatures below the critical temperature (T c ), indicating the absence of the BKT transition. Subsequently, however, it was shown that at low currents the addition of current noise can turn nonlinear I-V curves into ohmic behavior [9]. Thus, it is easy to confuse nonlinear I-V tails generated by noise with non-ohmic tails expected from the BKT transition. Moreover, it was recently shown that the size effects may radically alter the I-V curves of superconducting films [10] so that they mimic the dc BKT behavior. Thus, it is important to understand that nonlinear I-V characterizes per se cannot prove the occurrence of the BKT transition; one needs to see a concurrent sharp drop in the superfluid density.Further, it was noted that a precondition [8] for the BKT transition to occur in a superconductor, i.e., that the sample size L s < λ eff , where λ eff = 2λ 2 /d is the effective (Pearl) penetration depth and d is the film thickness, is not satisfied even in 1 UC thick YBCO films [11]. N...

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Berezinskii-Kosterlitz-Thouless transition and fluctuation paraconductivity in Y1Ba2Cu3O7 single crystal films

Cited by 33 publications

References 27 publications

Quasi-two-dimensional superconductivity in FeSe0.3Te0.7 thin films and electric-field modulation of superconducting transition

Quasi-two-dimensional superconductivity in FeSe0.3Te0.7 thin films and electric-field modulation of superconducting transition

Nonlinear Interaction of the Electromagnetic Waves Irradiating the Plate of a Hard Superconductor From the Opposite Sides

Complex conductance of ultrathin La2–xSrxCuO4 films and heterostructures

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