Field Dependence of the Vortex Core Size in a Multiband Superconductor

Callaghan, F. D.; Laulajainen, M.; Kaiser, C. V.; Sonier, J. E.

doi:10.1103/physrevlett.95.197001

Cited by 51 publications

(80 citation statements)

References 41 publications

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“…By imposing the following simple model, excellent agreement between these two very different kinds of measurements has been demonstrated [41]:…”

Section: Thermal Conductivitymentioning

confidence: 99%

“…Instead it is an indication that the theoretical model for n(B) does not contain all of the relevant physics. On the other hand, a "true" measure of the magnetic penetration depth in a µSR experiment has been demonstrated to be given by the H → 0 extrapolated value of λ ab [41,42]. In other words, when an inadequate model for n(B) is used to fit the TF-µSR signal, the difference between λ ab and the magnetic penetration depth grows with increasing magnetic field.…”

Section: Magnetic Field Dependence Of λ Abmentioning

confidence: 99%

“…This point was made in Refs. [23,37,38,39,40,41,42,43,44,45]. For this reason, the magnetic penetration depth actually corresponds to the extrapolated H → 0 value of λ.…”

Section: Full Line Shape Analysismentioning

confidence: 99%

“…Their model predicts that in clean high-κ superconductors, the intrinsic superconducting coherence length is not independent of magnetic field, but actually decreases with increasing field. Recently, DeBeer-Schmitt et al [88] measured an unusual field-independent FLL form factor in CeCoIn 5 by small-angle neutron scattering, suggestive of a field-dependent coherence length (see (14) from µSR measurements on single crystals of (a) V3Si [64], (b) NbSe2 [41], and (c) LuNi2B2C [55]. All measurements were done with the applied field parallel to theĉ-axis.…”

Section: Vortex Core Sizementioning

confidence: 99%

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Muon spin rotation studies of electronic excitations and magnetism in the vortex cores of superconductors

Sonier

2007

Rep. Prog. Phys.

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The focus of this article is on recent progress in muon spin rotation (µSR) studies of the vortex cores in type-II superconductors. By comparison of µSR measurements of the vortex-core size in a variety of materials with results from techniques that directly probe electronic states, the effect of delocalized quasiparticles on the spatial variation of field in a lattice of interacting vortices has been determined for both single-band and multi-band superconductors. These studies demonstrate the remarkable accuracy of what some still consider an exotic technique. In recent years µSR has also been used to search for magnetism in and around the vortex cores of high-temperature superconductors. As a local probe µSR is specially suited for detecting static or quasistatic magnetism having short-range or random spatial correlations. As discussed in this review, µSR experiments support a generic phase diagram of competing superconducting and magnetic order parameters, characterized by a quantum phase transition to a state where the competing order is spatially non-uniform.

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“…By imposing the following simple model, excellent agreement between these two very different kinds of measurements has been demonstrated [41]:…”

Section: Thermal Conductivitymentioning

confidence: 99%

Section: Magnetic Field Dependence Of λ Abmentioning

confidence: 99%

“…This point was made in Refs. [23,37,38,39,40,41,42,43,44,45]. For this reason, the magnetic penetration depth actually corresponds to the extrapolated H → 0 value of λ.…”

Section: Full Line Shape Analysismentioning

confidence: 99%

Section: Vortex Core Sizementioning

confidence: 99%

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Muon spin rotation studies of electronic excitations and magnetism in the vortex cores of superconductors

Sonier

2007

Rep. Prog. Phys.

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“…The GL coherence length ξ ab ∼ 26Å calculated from the upper critical field H c2 ∼ 50 T of BaFe 1.84 Co 0.16 As 2 with H c [6], represents a lower limit for the vortex core radius [3]. The core size can be much larger if there are spatially extended quasiparticle core states associated with either the existence of a second smaller superconducting gap [7] or a single anisotropic gap [8]. Yet fits of the TF-µSR spectra of BaFe 1.82 Co 0.18 As 2 using Eq.…”

mentioning

confidence: 99%

Magnetism and Disorder Effects on Muon Spin Rotation Measurements of the Magnetic Penetration Depth in Iron-Arsenic Superconductors

et al. 2011

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It is shown that attempts to accurately deduce the magnetic penetration depth λ of overdoped BaFe1.82Co0.18As2 single crystals by transverse-field muon spin rotation (TF-µSR) are thwarted by field-induced magnetic order and strong vortex-lattice disorder. We explain how substantial deviations from the magnetic field distribution of a nearly perfect vortex lattice by one or both of these factors is also significant for other iron-based superconductors, and this introduces considerable uncertainty in the values of λ obtained by 74.25.Ha, 76.75.+i TF-µSR is routinely used to determine the magnetic penetration depth λ of type-II superconductors in the vortex state for the purpose of obtaining indirect information on the energy gap structure [1]. The magnetic field distribution n(B) in the sample is determined by detecting the decay positrons from implanted positive muons that locally probe the internal fields, and λ is subsequently determined by modeling the contribution of the vortex lattice (VL) to n(B). However, even in conventional superconductors the VL contribution is not known a priori, and one must rely on phenomenological models to deduce what is really an "effective" penetration depthλ. One reason for this is that only cumbersome microscopic theories account for the effects of low-energy excitations on n(B) [2]. Extrapolating low-temperature measurements ofλ to zero field to eliminate the effects of intervortex transfer of quasiparticles, as well as nonlocal and nonlinear effects, has been demonstrated to be an accurate way of determining the "true" magnetic penetration depth λ [3,4]. Yet an underlying assumption is always that the VL is highly ordered and that other contributions to n(B) are relatively minor. The purpose of this Letter is to point out that this is not the case in many of the recently discovered iron-based superconductors, making a reliable determination of λ by TF-µSR extremely difficult.Here we report on representative TF-µSR measurements of BaFe 1.82 Co 0.18 As 2 (T c = 21 K) single crystals grown from a FeAs flux, as described elsewhere [5]. High-statistics TF-µSR spectra of 20 million muon decay events were collected in magnetic fields H = 0.02 T to 0.5 T applied transverse to the initial muon spin polarization P (t = 0), and parallel to the c-axis of the crystals. The TF-µSR signal is the time evolution of the muon spin polarization, and is related to n(B) as followswhere γ µ is the muon gyromagnetic ratio. Generally, the TF-µSR signal is fit in the time domain, with the inverse Fourier transform or "TF-µSR line shape" given byproviding a visual approximation of the internal field distribution. The field distribution of a perfectly ordered VL is characterized by sharp cutoffs at the minimum and maximum values of B(r), and a sharp peak at the saddlepoint value of B(r) [1]. These features are not observed in polycrystalline samples, where the orientation of the crystal lattice varies with respect to H, but are observed in single crystals when a highly-ordered VL exists and other co...

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Surface structure and multigap superconductivity of V3Si (111) revealed by scanning tunneling microscopy

et al. 2023

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V3Si, a classical silicide superconductor with relatively high $T_{\mathrm{C}}$ T C (∼16 K), is promising for constructing silicon-based superconducting devices and hetero-structures. However, real space characterization on its surfaces and superconducting properties are still limited. Here we report the first low-temperature scanning tunnelling microscopy (STM) study on cleaned V3Si (111) single crystal surface. We observed a $\sqrt{3} \times \sqrt{3}$ 3 × 3 superstructure which displays mirror symmetry between adjacent terraces, indicating the surface is V-terminated and reconstructed. The tunneling spectrum shows full superconducting gap with double pairs of coherence peaks, but has a relatively small gap size with comparing to bulk $T_{\mathrm{C}}$ T C . Impurity induced in-gap state is absent on surface defects but present on introduced magnetic adatoms. Upon applying magnetic field, a hexagonal vortex lattice is visualized. Interestingly, the vortex size is found to be field dependent, and the coherence length measured from single vortex at low field is significantly larger than estimated value from bulk $H_{c2}$ H c 2 . These results reflect V3Si is a multi-band, s-wave superconductor.

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Field Dependence of the Vortex Core Size in a Multiband Superconductor

Cited by 51 publications

References 41 publications

Muon spin rotation studies of electronic excitations and magnetism in the vortex cores of superconductors

Muon spin rotation studies of electronic excitations and magnetism in the vortex cores of superconductors

Magnetism and Disorder Effects on Muon Spin Rotation Measurements of the Magnetic Penetration Depth in Iron-Arsenic Superconductors

Surface structure and multigap superconductivity of V3Si (111) revealed by scanning tunneling microscopy

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