Vortex dynamics in type-II superconductors under strong pinning conditions

Thomann, A. U.; Geshkenbeǐn, V. B.; Blatter, G.

doi:10.1103/physrevb.96.144516

Cited by 22 publications

(26 citation statements)

References 42 publications

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“…Fc near the velocity v th and then slowly decays, in agreement with the theoretical prediction [14]. manifests in the data as a saturation of the differential resistance, see Fig.…”

Section: K) Rises Steeply Towards the Maximum Valuesupporting

confidence: 89%

“…Upon decreasing the field below the 3D strong pinning condition n p S trap a 0 < 1, pinning turns one-dimensional (1D) and j c is expected to saturate to a B-independent value. Taking into account a weak κ-dependence of the transverse trapping t ⊥ ∼ κ 1/4 ξ [14] changes the field-scaling of the critical current density to j c ∝ B −α with α = 5/8 for a Lorentzianshaped pinning potential. This result has been verified and augmented by numerical simulations [24] showing that the exponent α in fact decreases for increasing defect densities or vortex core size.…”

Section: Parameters From Strong Pinning Theorymentioning

confidence: 99%

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Experimental test of strong pinning and creep in current-voltage characteristics of type-II superconductors

et al. 2019

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Pinning and creep determine the current-voltage characteristic of a type II superconductor and thereby its potential for technological applications. The recent development of strong pinning theory provides us with a tool to assess a superconductor's electric properties in a quantitative way. Motivated by the observation of typical excess-current characteristics and field-scaling of critical currents, here, we analyze current-voltage characteristics measured on 2H-NbSe2 and a-MoGe type II superconductors within the setting provided by strong pinning theory. The experimentally observed shift and rounding of the voltage-onset is consistent with the predictions of strong pinning in the presence of thermal fluctuations. We find the underlying parameters determining pinning and creep and discuss their consistency.

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“…Fc near the velocity v th and then slowly decays, in agreement with the theoretical prediction [14]. manifests in the data as a saturation of the differential resistance, see Fig.…”

Section: K) Rises Steeply Towards the Maximum Valuesupporting

confidence: 89%

Section: Parameters From Strong Pinning Theorymentioning

confidence: 99%

Experimental test of strong pinning and creep in current-voltage characteristics of type-II superconductors

et al. 2019

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“…Next, we choose the vortex position along the x-axis, R 0 = x e x and assume a radially symmetric pin, implying that u 0 = u e x ; expressing the effective free energy in Eq. (12) in terms of the vortex tip coordinate r = x + u, we arrive at the simplified effective pinning energy…”

Section: A Strong Pinningmentioning

confidence: 99%

Strong pinning theory of thermal vortex creep in type-II superconductors

et al. 2019

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We study thermal effects on pinning and creep in type-II superconductors where vortices interact with a low density np of strong point-like defects with pinning energy ep and extension ξ, the vortex core size. Defects are classified as strong if the interaction between a single pin and an individual vortex leads to the appearance of bistable solutions describing pinned and free vortex configurations. Extending the strong pinning theory to account for thermal fluctuations, we provide a quantitative analysis of vortex depinning and creep. We determine the thermally activated transitions between bistable states using Kramer's rate theory and find the non-equilibrium steady-state occupation of vortex states. The latter depends on the temperature T and vortex velocity v and determines the current-voltage (or force-velocity) characteristic of the superconductor at finite temperatures. We find that the T = 0 linear excess-current characteristic v ∝ (j − jc) Θ(j − jc) with its sharp transition at the critical current density jc, keeps its overall shape but is modified in three ways due to thermal creep: a downward renormalization of jc to the thermal depinning current density j dp (T ) < jc, a smooth rounding of the characteristic around j dp (T ), and the appearance of thermally assisted flux flow (TAFF) v ∝ j exp(−U0/kBT ) at small drive j jc, with the activation barrier U0 defined through the energy landscape at the intersection of free and pinned branches. This characteristic emphasizes the persistence of pinning of creep at current densities beyond critical. arXiv:1903.09083v2 [cond-mat.supr-con]

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“…Matsushita indicates that based on the analysis Kramer can be concluded that there are two types of high-field pinning centers dependent on the strength of pinning [14]. Blatter et al [1], Kwok et al [15], and Thomann et al [16] also conducted research and theoretical analysis on strong pinning centers in high-temperature superconductor materials. Blatter et al [1] suggested that the most prominent type of strong pinning to date is pinning by columnar defects.…”

Section: Introductionmentioning

confidence: 99%

“…Kwok et al [15] indicated that irradiation defects only improve pinning at high magnetic fields and not at very high temperatures. Thomann et al [16] showed that strong pinning is dependent on dynamics of the vortex lattice. Klaassen et al [17] also indicated linear defects create strong pinning centers.…”

Section: Introductionmentioning

confidence: 99%

Analysis Method of High-Field Pinning Centers in NbTi Wires and MgB2 Wires

Gajda

2018

J Low Temp Phys

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The main purpose of this article is to show an easier and more accurate method for analyzing high-field pinning centers. Previous methods did not allow for precise analysis and research on high-field pinning centers, they studied only the dominant pinning mechanism, and they required a maximum of pinning force (F pmax) to analyze pinning centers. The main advantage of this method can be used in samples without the maximum pinning force required by other methods to analyze the pinning mechanism. In addition, this method allows us to observe even small changes in the density of individual pinning centers. This method is based on analysis of critical current density values in different ranges of reduced magnetic field. The method of analysis of highfield pinning centers allows primarily to develop methods and directions for creation of high-field pinning centers. The surface pinning centers are strong pinning centers in low magnetic fields and very weak pinning centers in middle and high magnetic fields. Additionally, the analysis of pinning centers shows that dislocations, strains, substitutions in the crystal lattice, and precipitation inside the grains create strong pinning centers in high magnetic fields and very weak pinning centers in low and middle magnetic fields. Research indicates that strains, substitutions in the crystal lattice, and precipitates inside grains form pinning centers that operate in the high magnetic field range.

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Vortex dynamics in type-II superconductors under strong pinning conditions

Cited by 22 publications

References 42 publications

Experimental test of strong pinning and creep in current-voltage characteristics of type-II superconductors

Experimental test of strong pinning and creep in current-voltage characteristics of type-II superconductors

Strong pinning theory of thermal vortex creep in type-II superconductors

Analysis Method of High-Field Pinning Centers in NbTi Wires and MgB2 Wires

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