Conductance noise and percolation in YBa2Cu3O7 thin films

Kiss, L.B.; Larsson, T.; Svedlindh, Peter; Lundgren, L.; Ohlsén, H.; Ottosson, Mikael; Hudner, J.; Stolt, Lars

doi:10.1016/0921-4534(93)90314-g

Cited by 41 publications

(21 citation statements)

References 37 publications

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“…Deep in the superconducting phase (low fields), the scaling follows the prediction for a ''classical'' RS network in 3D of l rs ¼ 0:9 AE 0:3 [27], whereas the slope when approaching superconductivity from above (high fields) is significantly larger. The slope we observe is close to the characteristic exponent of l rs ¼ 2:74 for the so-called p model in 3D [27,29], which has been first observed for thin-film high-T c superconductors. p noise, leading to a new class of universal scaling exponents, in the above-described picture corresponds to a random switching (on-off) of superconducting links in the RS network, i.e., spontaneous fluctuations ÁpðtÞ of pðTÞ leading to fluctuations in the macroscopic resistance, which may be due to time-dependent perturbations of the Josephson coupling energy between superconducting clusters.…”

supporting

confidence: 86%

Magnetic-Field Induced Crossover of Superconducting Percolation Regimes in the Layered Organic Mott Systemκ−(BEDT−TTF)2Cu[
Müller
¹
,
Brandenburg
²
,
Schlueter
³

2009
Phys. Rev. Lett.
30
5
34
0
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Fluctuation spectroscopy is used to investigate the organic bandwidth-controlled Mott system kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Cl. We find evidence for percolative-type superconductivity in the spatially inhomogeneous coexistence region of antiferromagnetic insulating and superconducting states. When the superconducting transition is driven by a magnetic field, percolation seems to be dominated by instable superconducting clusters upon approaching T(c)(B) from above, before a "classical" type of percolation is resumed at low fields, dominated by the fractional change of superconducting clusters. The 1/f noise is resolved into Lorentzian spectra in the crossover region, where the action of an individual fluctuator is enhanced, pointing to a mesoscopic phase separation.

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supporting

confidence: 86%

Magnetic-Field Induced Crossover of Superconducting Percolation Regimes in the Layered Organic Mott Systemκ−(BEDT−TTF)2Cu[
Müller
¹
,
Brandenburg
²
,
Schlueter
³

2009
Phys. Rev. Lett.
30
5
34
0
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“…The noise in these systems arise from two possible scenarios : a) resistance fluctuations in regions of normal metal and b) fluctuations in the number of superconducting regions/islands. It is well known from the theory of percolation that noise grows till the film becomes fully superconducting [27][28][29][30]. The noise follows the relation δR 2 /R 2 ∝ R −lrs where the percolation ex- ponent l rs ∼ 1 ± 0.4 in our experiments.…”

mentioning

confidence: 64%

Correlated Conductance Fluctuations Close to the Berezinskii-Kosterlitz-Thouless Transition in Ultrathin NbN Films

et al. 2013

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We probe the presence of long-range correlations in phase fluctuations by analyzing the higherorder spectrum of resistance fluctuations in ultra-thin NbN superconducting films. The nonGaussian component of resistance fluctuations is found to be sensitive to film thickness close to the transition, which allows us to distinguish between mean field and Berezinskii-Kosterlitz-Thouless (BKT) type superconducting transitions. The extent of non-Gaussianity was found to be bounded by the BKT and mean field transition temperatures and depend strongly on the roughness and structural inhomogeneity of the superconducting films. Our experiment outlines a novel fluctuation-based kinetic probe in detecting the nature of superconductivity in disordered low-dimensional materials.The transition from superconducting to normal state in two-dimensions is known to occur via BerezinskiiKosterlitz-Thouless (BKT) mechanism. Traditionally, the signature of BKT transition is found by measuring the superfluid density where a discontinuity is observed at the critical temperature T BKT [1][2][3]. This method is limited in its scope of application for systems exhibiting interfacial/buried superconductivity like oxide heterostructures due to the inability to measure the thickness of the superconducting layer accurately. Transport-based probes including discontinuity in the power law behavior of I-V characteristics or change in the curvature of magnetoresistance from convex to concave in the presence of a perpendicular magnetic field [4][5][6][7][8][9] have their limitations as real systems contain some degree of inhomogeneity which smear out the signatures of BKT type behavior. With growing interest in lowdimensional superconductivity, it is interesting to develop new probes/techniques that are not only sensitive enough to detect BKT transition but also compare its characteristics scales with the mean field description.The BKT transition, as exhibited by ultra-thin superconducting films, is characterized by the unbinding of vortex pairs beyond T BKT . It is well known that these vortices exhibit long-range interactions which vary logarithmically with the distance between the vortices. Vortices also occur in bulk Type-II superconductors in the presence of an external magnetic field. Earlier experiments probing vortices in bulk films through measurements of flux flow noise and voltage noise have reported the presence of broad band noise (BBN) [10,11] as a function of driving current and magnetic field. The statistics of noise in these systems is non-Gaussian due to the fact that most of the noise arise from very few fluctuators. Noise measurements on quasi-2D MgB 2 films show a possibility of thermally induced vortex hopping through measurements of flux noise close to BKT transition [12]. To the best of our knowledge there are no reports on higher-order statistics of fluctuations looking into the possibility of interacting vortices in two-dimensions.Higher-order fluctuations in resistivity has been established as an useful tool to study the pres...

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“…(3). As a consequence, the normalized noise of these materials has decreased by 5-8 orders in magnitude [20] which in turn has made it possible to distinguish other noise sources than the source considered in classical percolation noise models.…”

Section: New Noise Exponents In Random Conductor-superconductor and Cmentioning

confidence: 99%

“…Recent experimental results [20,21] of conductance noise in high-quality high-TV superconducting thin films have shown that the noise exponent can be much larger than the scaling exponents predicted by classical percolation models [l rs in Eq. (4a)].…”

Section: New Noise Exponents In Random Conductor-superconductor and Cmentioning

confidence: 99%

New noise exponents in random conductor-superconductor and conductor-insulator mixtures

Kiss

Svedlindh

1993

Phys. Rev. Lett.

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Time dependent fluctuations of the fraction of normal-conducting part in random resistorsuperconductor (RS) and resistor-insulator (RI) networks lead to a novel effect close to the percolation threshold. The normalized noise scales as a function of the resistance with a characteristic exponent X. The value of X is different from the value found in classical percolation models but can be related to the resistivity exponent s (t) of the RS (RI) transition by a simple scaling relation: X=2/s (2/t). Results of recent experiments on high-r c superconducting thin films are interpreted in terms of this new effect and a crossover from three to two dimensional percolation behavior is found.PACS numbers: 74.40.+k, 64.60.Ak, 72.70.+m, 74.76.Bz The electrical conductance and conductance noise in random resistor-superconductor (RS) and resistor-insulator (RI) composites have been extensively studied during the last decade [1][2][3][4][5][6][7][8][9][10]. Such studies are interesting not only for fundamental reasons but also for technological applications. An important example of such materials is high-T c superconductors, which show a random RS composite nature in the superconducting transition region (e.g., [11][12][13][14]). Another example is thick film resistors [15][16][17][18][19], which are widely used in electronics. Such resistors consist of metal particles embedded in a glass medium and behave as random RI composites [19].Random resistor networks are applied in modeling the physical behavior of granular superconductors and metal-insulator composites [1-10]. One can start from a spatially homogeneous lattice of resistors representing a homogeneous material. Introducing short circuits parallel to some resistor elements, selected at random, yields a network representing a random RS mixture. Cutting out some resistors, selected at random, yields a network representing a random RI mixture.The physics of random resistor networks is governed by the characteristic cluster size § of the superconducting phase in RS composites and of the conducting phase in RI composites. In the percolation region, these length scales can be expressed as a function of the volume frac-tion p r of resistors (0 :< p r < 1), ^rs cc (pr-Pcr)~V (pr > Per) and €ri « (Pr -Per) ~V (pr > Per) ,(lb)where pc r = 1 -p cs , p C s is the percolation threshold of the superconductor component, p cr is the percolation threshold of the conducting component, and v is a critical exponent (v-j in 2D; v=0.89±0.01 in 3D). This critical behavior leads to the following scaling behavior of the macroscopic resistance R: pr>Per) andRri « (Pr -Per) ' (pr > Per)where R rs is the resistance of the RS composite and R ri is the resistance of the RI composite. Values of the universal exponents s and t [1-10] are shown in Table I. Studies of noise in classical percolation models are based on the assumptions that the resistor elements in the network fluctuate independently of each other and that the fluctuation is small in comparison to the mean value of the resistance, ...

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Conductance noise and percolation in YBa2Cu3O7 thin films

Cited by 41 publications

References 37 publications

Magnetic-Field Induced Crossover of Superconducting Percolation Regimes in the Layered Organic Mott Systemκ−(BEDT−TTF)2Cu[
Müller
¹
,
Brandenburg
²
,
Schlueter
³

2009
Phys. Rev. Lett.
30
5
34
0
View full text Add to dashboard Cite

Magnetic-Field Induced Crossover of Superconducting Percolation Regimes in the Layered Organic Mott Systemκ−(BEDT−TTF)2Cu[
Müller
¹
,
Brandenburg
²
,
Schlueter
³

2009
Phys. Rev. Lett.
30
5
34
0
View full text Add to dashboard Cite

Correlated Conductance Fluctuations Close to the Berezinskii-Kosterlitz-Thouless Transition in Ultrathin NbN Films

New noise exponents in random conductor-superconductor and conductor-insulator mixtures

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Conductance noise and percolation in YBa2Cu3O7 thin films

Cited by 41 publications

References 37 publications

Magnetic-Field Induced Crossover of Superconducting Percolation Regimes in the Layered Organic Mott Systemκ−(BEDT−TTF)2Cu[Müller1, Brandenburg2, Schlueter3 2009Phys. Rev. Lett.305340View full textAdd to dashboardCite

Magnetic-Field Induced Crossover of Superconducting Percolation Regimes in the Layered Organic Mott Systemκ−(BEDT−TTF)2Cu[Müller1, Brandenburg2, Schlueter3 2009Phys. Rev. Lett.305340View full textAdd to dashboardCite

Correlated Conductance Fluctuations Close to the Berezinskii-Kosterlitz-Thouless Transition in Ultrathin NbN Films

New noise exponents in random conductor-superconductor and conductor-insulator mixtures

Contact Info

Product

Resources

About

Magnetic-Field Induced Crossover of Superconducting Percolation Regimes in the Layered Organic Mott Systemκ−(BEDT−TTF)2Cu[
Müller
¹
,
Brandenburg
²
,
Schlueter
³

2009
Phys. Rev. Lett.
30
5
34
0
View full text Add to dashboard Cite

Magnetic-Field Induced Crossover of Superconducting Percolation Regimes in the Layered Organic Mott Systemκ−(BEDT−TTF)2Cu[
Müller
¹
,
Brandenburg
²
,
Schlueter
³

2009
Phys. Rev. Lett.
30
5
34
0
View full text Add to dashboard Cite