Damping of the de Haas–van Alphen oscillations in the superconducting state of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">Mg</mml:mi><mml:msub><mml:mi mathvariant="normal">B</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>

Fletcher, J. D.; Carrington, A.; Казаков, С. М.; Karpiński, J.

doi:10.1103/physrevb.70.144501

Cited by 16 publications

(21 citation statements)

References 54 publications

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“…Using an average Fermi velocity of ν F = 4.8 × 10 5 ms −1 25 26 , and a density of states N (0) = 0.7 eV −1 unit cell −1 27 28 , with residual resistivity data ρ 77nm (27 K) = 39.0 ± 0.5 μ Ωcm and ρ 160nm (36 K) = 14.88 ± 0.02 μ Ωcm we estimate nm and nm in the 77 nm and 160 nm films respectively. As expected these are far shorter than estimates for single crystals in the literature which lie in the range nm 29 30 31 32 33 34 . The high scattering-rate scenario is best illustrated by the dramatically reduced zero-field critical temperature of the 77 nm film with respect to the 160 nm film and single crystals, ( K K K) 16 , which is a well-known consequence of increased interband scattering in two-band superconductors 23 35 36 .…”

Section: Experimental Methodssupporting

confidence: 56%

Spontaneous symmetry breaking in vortex systems with two repulsive lengthscales

Curran

Desoky

Miloševıć

et al. 2015

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Scanning Hall probe microscopy (SHPM) has been used to study vortex structures in thin epitaxial films of the superconductor MgB2. Unusual vortex patterns observed in MgB2 single crystals have previously been attributed to a competition between short-range repulsive and long-range attractive vortex-vortex interactions in this two band superconductor; the type 1.5 superconductivity scenario. Our films have much higher levels of disorder than bulk single crystals and therefore both superconducting condensates are expected to be pushed deep into the type 2 regime with purely repulsive vortex interactions. We observe broken symmetry vortex patterns at low fields in all samples after field-cooling from above Tc. These are consistent with those seen in systems with competing repulsions on disparate length scales, and remarkably similar structures are reproduced in dirty two band Ginzburg-Landau calculations, where the simulation parameters have been defined by experimental observations. This suggests that in our dirty MgB2 films, the symmetry of the vortex structures is broken by the presence of vortex repulsions with two different lengthscales, originating from the two distinct superconducting condensates. This represents an entirely new mechanism for spontaneous symmetry breaking in systems of superconducting vortices, with important implications for pinning phenomena and high current density applications.

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Section: Experimental Methodssupporting

confidence: 56%

Spontaneous symmetry breaking in vortex systems with two repulsive lengthscales

Curran

Desoky

Miloševıć

et al. 2015

Sci Rep

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“…There is no problem with seeing quantum oscillations as set by the large Fermi surface present in strongly overdoped HTSC material, provided one is able to go to sufficiently high magnetic fields (> H irrev ). dHvA and SdH studies on strong coupling superconductors have become routine since the ground breaking work on 2H-NbSe 2 [45], even though H might stand below H c2 . Very recently Vignolle et al [17] have managed to secure both magneto-resistance and magnetic torque oscillations from small, high quality (RRR~20), highly overdoped Tl-2201 crystals, with T c ≈ 10 K, by working at sub-4.2 K temperatures and in fields of between 50 and 60 tesla (here > H c2 ).…”

Section: §1 Background To Negative-u Modelling Of Htsc Phenomenamentioning

confidence: 99%

Elucidation of the origins of transport behaviour and quantum oscillations in high temperature superconducting cuprates

Wilson

2009

J. Phys.: Condens. Matter

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A detailed exposition is given of recent transport and 'quantum oscillation' results from high temperature superconducting (HTSC) systems covering the full carrier range from overdoped to underdoped material. This now very extensive and high quality data set is here interpreted within the framework developed by the author of local pairs and boson-fermion resonance, arising in the context of negative- U behaviour within an inhomogeneous electronic environment. The strong inhomogeneity comes with the mixed-valence condition of these materials, which when underdoped lie in close proximity to the Mott-Anderson transition. The observed intense scattering is presented as resulting from pair formation and from electron-boson collisions in the resonant crossover circumstance. The high level of scattering carries the systems to incoherence in the pseudogapped state, p

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“…The angular dependence of H c2 was then fitted to the anisotropic Ginzburg-Landau form to give γ ξ . Extracting H c2 from the torque measurements [3,14] is more difficult than for heat capacity as pinning effects, especially at low temperature, complicate the behavior close to H c2 . We find however, that in the region of overlap there is good agreement between the two techniques.…”

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confidence: 99%

“…Some crystals used in this study are from the same batch as those used in de Haas-van Alphen studies [14], and are hence known to be of high quality, with mean free paths of ℓ π ≃ 850Å, ℓ σ ≃ 500Å. The T c of the crystals, as determined from the midpoint of the heat capacity anomaly, was 38.3 K. Measurements of the temperature dependent penetration depth were performed using a tunnel diode oscillator technique operating at 11.7 MHz [15].…”

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Temperature-Dependent Anisotropy of the Penetration Depth and Coherence Length ofMgB2

et al. 2005

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We report measurements of the temperature dependent anisotropies (γ λ and γ ξ ) of both the London penetration depth λ and the upper critical field of MgB2. Data for γ λ = λc/λa was obtained from measurements of λa and λc on a single crystal sample using a tunnel diode oscillator technique. γ ξ = H c c2 /H ⊥c c2 was deduced from field dependent specific heat measurements on the same sample. γ λ and γ ξ have opposite temperature dependencies, but close to Tc tend to a common value (γ λ ≃ γ ξ = 1.75 ± 0.05). These results are in good agreement with theories accounting for the two gap nature of MgB2.The existence of two superconducting gaps in MgB 2 [1] leads to an unusually strong temperature dependence in the anisotropy of the upper critical field, Refs. 2,3,4,5). The maximum value of γ ξ ≃ 6 is found at the lowest temperatures where it is dominated by the anisotropy in the quasi two dimensional σ bands. At higher temperatures, γ ξ is substantially reduced due to the increasing contribution of the more isotropic π band [5]. The anisotropy of the penetration depth, γ λ = λ c /λ a , is predicted to have a markedly different temperature dependence to that of H c2 [4,6]. At zero temperature, in the clean local limit, the anisotropy in the penetration depth is determined only by the anisotropy in the Fermi velocity v F and not by the anisotropy in the gap [7]. Band structure calculations [8] show that the average v F is approximately isotropic suggesting that λ is similarly isotropic at low temperature [4]. As temperature is increased it has been predicted [4,6] that γ λ increases markedly because of the more rapid reduction of the superfluid density on the π sheets (where the gap is smaller) than on the σ sheets.There have been several experimental measurements of the temperature dependence of γ ξ . Although there were some disagreements in early measurements, the most recent data [2, 3, 9] agree well with the theoretical predictions [4,5]. Significantly less experimental data has been reported on γ λ . Measurements of the distortion of the vortex lattice by neutron scattering [10] and scanning tunneling spectroscopy [11] suggest that at low temperature the anisotropy is small, γ λ = 1.2 ± 0.1. γ λ has also been estimated from the anisotropy of H c1 (γ Hc1 = H c c1 /H ⊥c c1 ). There has been some disagreement between different studies (see Ref. 12) but recent data [12] suggest that at low T , γ Hc1 ≃ 1 and there is an upward trend in γ Hc1 near T c . However, γ Hc1 may not be simply related to γ λ in MgB 2 because of two gap effects. In this paper, we present direct measurements of the temperature dependencies of λ a and λ c in single crystal samples of MgB 2 in the Meissner state, using a sensitive radio frequency technique. Our data show that γ λ increases as T → T c , in agreement with theoretical predictions. Measurements of H c2 anisotropy in the same crystals show that the values of γ λ and γ ξ converge as T → T c .Single crystals of MgB 2 were grown using a high pressure technique described elsewhere [13]. Som...

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Damping of the de Haas–van Alphen oscillations in the superconducting state ofMgB2

Cited by 16 publications

References 54 publications

Spontaneous symmetry breaking in vortex systems with two repulsive lengthscales

Spontaneous symmetry breaking in vortex systems with two repulsive lengthscales

Elucidation of the origins of transport behaviour and quantum oscillations in high temperature superconducting cuprates

Temperature-Dependent Anisotropy of the Penetration Depth and Coherence Length ofMgB2

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