Superconducting vortices in triangular and square Josephson junction arrays

Martinoli, P.; Théron, Ricardo; Simond, J. B.; Meyer, Robert B.; Jaccard, Y.; Leemann, Ch.

doi:10.1088/0031-8949/1993/t49a/029

Cited by 6 publications

(8 citation statements)

References 16 publications

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“…At this stage it is not clear how to observe experimentally the loss of interplane coherence in layered superconductors. The most promising quantitity for measuring the helicity modulus seems to be the complex impedance [22], although it might be difficult to isolate experimentally a specific component of the helicity tensor, in particular, a tiny value of Y Ќ .…”

Section: Friedel Transition In Layered Superconductorsmentioning

confidence: 99%

Friedel Transition in Layered Superconductors

et al. 1996

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Weakly coupled superconducting layers are described by the anisotropic 3D XY model. A lowtemperature layer decoupling due to a proliferation of fluxons between planes, as proposed by Friedel, does not occur. The same is true for a periodic superlattice of high and low T c layers, although the interplane coherence can become extremely weak. On the other hand a true layer decoupling is found for a random stack. [S0031-9007(96)01487-1] PACS numbers: 74.20.De, 74.80.Dm The Berezinskii-Kosterlitz-Thouless (BKT) transition [1,2], mediated by the unbinding of vortex pairs, has been clearly observed in superfluid films [3]. More recently, nonlinear transport experiments in layered hightemperature superconductors [4] have also shown typical signatures of vortex unbinding slightly below the critical temperature T c . This is surprising, since the Josephson coupling between the layers renders the system three dimensional, in particular close to T c . Specific heat experiments for YBCO single crystals indeed give evidence for three-dimensional critical behavior [5].Some time ago Friedel [6] argued that the interlayer coupling could be effectively suppressed by a proliferation of Josephson vortex loops or fluxons between the layers. A simple estimate for the fluxon energy suggests that the layers are decoupled at a temperature T ‫ء‬ , T c , so that there would be a two-dimensional regime for T ‫ء‬ , T , T c , with a BKT transition at T c . Unfortunately, a closer look at the problem [7] indicates that this "Friedel transition" does not occur below T c [8]. Therefore the question arises why nevertheless in nonlinear transport experiments BKT signatures are clearly observed. A way out of this dilemma has been offered by Jensen and Minnhagen [9], who realized that the Lorentz force acting on the vortices can overcome the interlayer confinement of vortex pairs.In this Letter we study again the possible existence of a two-dimensional regime below the critical temperature, starting from the classical XY model with strong intralayer coupling J k and weak interlayer coupling J Ќ . A simple criterion for the decoupling transition together with Monte Carlo simulations shows that a layer decoupling below T c does not occur, in agreement with previous studies [8]. We attribute this negative result to a strong increase of the fluxon energy as a function of temperature. We turn then to question whether a decoupling can be excluded on general grounds, by considering a superlattice of high and low T c layers [10]. For an ordered array a decoupling seems to occur around the low T c , but a closer look shows that this apparent transition is in reality a crossover from strong to weak interplane coherence. On the other hand, in a disordered array we do find a true layer decoupling.Incidentally, the problem is of more general relevance, as the question of long-range coherence arises also in other quantum systems. One can, for instance, ask whether a disordered layered system of electrons, with a large difference between the masses for the mot...

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Section: Friedel Transition In Layered Superconductorsmentioning

confidence: 99%

Friedel Transition in Layered Superconductors

et al. 1996

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“…Experimental studies of square Josephson junction arrays placed in a uniform magnetic field whose magnitude corresponds to half the magnetic flux quantum per lattice cell have been conducted by several researchers [161 ± 167]. Unfortunately, the methods used by these researchers (in particular, in studying the temperature dependence of both components of the complex-valued frequency-dependent impedance [161,162] and the exponent describing the behavior of the current±voltage characteristic in the smallcurrent limit [163,164]) allowed gathering information only about the superconducting transition but were not sensitive to the ordering of chiralities (at least when it occurred at T T dw b T v ).…”

Section: The Sequence Of Phase Transitionsmentioning

confidence: 99%

“…Although the earlier numerical simulation results do not always allow detecting the difference between T v and T dw [29,180], the results of more precise studies [175,181,182] confirm the conclusion that T v`Tdw . Unfortunately, as in the case of a square lattice, experimental investigation of triangular Josephson junction arrays placed in a magnetic field with a half-integer number of flux quanta per lattice cell [162] used methods that did not allow identifying the temperature at which ordering of chiralities occurs.…”

Section: March 2006mentioning

confidence: 99%

Untitled

Korshunov¹

2006

PHYS-USP

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We discuss the nature and sequence of phase transitions in two-dimensional systems with continuous degeneracy, in which other factors must be taken into account in addition to the interaction of point-like topological excitations, namely, the existence of an additional discrete degeneracy (which leads to the possibility of domain wall formation), the removal of accidental degeneracy by fluctuations, the formation of solitons, and the presence of a random potential acting on vortices. Formally, we discuss various modifications of the two-dimensional XY model, while physical objects that can be described by such models are various arrays of superconducting junctions and noncollinear planar antiferromagnets.

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“…7 As a consequence, a measurement of the real and imaginary components of Z ᮀ () as a function of f ͑at fixed and reasonably chosen temperature͒ produces strongly oscillating curves, [8][9][10][11][12] the well-developed dips on which correspond to the superconducting states.…”

Section: Introductionmentioning

confidence: 99%

“…8,9,12 This is related to suppression of vortex diffusion at temperatures for which the rate of a thermally activated tunneling of a vortex between neighboring lattice plaquettes ͑which requires it to overcome a well-defined barrier 13 ͒ becomes much smaller than the frequency of the measurement.…”

Section: Introductionmentioning

confidence: 99%

Magnetoinductance of Josephson junction array with frozen vortex diffusion

Korshunov

2003

Phys. Rev. B

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The dependence of sheet impedance of a Josephson junction array on an applied magnetic field is investigated in the regime when vortex diffusion between an array's plaquettes is effectively frozen due to a low enough temperature. The field-dependent correction to the sheet inductance is found to be proportional to f ln(1/f ), where f Ӷ1 is the magnitude of the field expressed in terms of flux quanta per plaquette.

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Superconducting vortices in triangular and square Josephson junction arrays

Cited by 6 publications

References 16 publications

Friedel Transition in Layered Superconductors

Friedel Transition in Layered Superconductors

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Magnetoinductance of Josephson junction array with frozen vortex diffusion

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