Nature of the superconductor–insulator transition in disordered superconductors

Dubi, Yonatan; Meir, Yigal; Avishai, Y.

doi:10.1038/nature06180

Cited by 365 publications

(395 citation statements)

References 33 publications

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“…We also note that the superconducting islands we found in the "normal" phase (which is really insulating) have also been observed in numerical studies of superconductor-insulator transition in disordered superconductors. 43 Our results are in qualitative agreement with previous studies 31,32 which suggested that the the FFLO state can survive as long as the electron scattering rate is comparable or smaller than the BCS gap. In our study we find the critical disorder strength W c ≈ 2.0; this corresponds to a scattering rate (within effective mass approximation) 1/τ c ≈ W 2 c /(24 t) ≈ 0.167 (we set = 1), which is indeed comparable the the BCS gap ∆ = 0.365.…”

Section: Discussionsupporting

confidence: 83%

Fulde-Ferrell-Larkin-Ovchinnikov state in disordereds-wave superconductors

Cui

Yang

2008

Phys. Rev. B

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The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state is a superconducting state stabilized by a large Zeeman splitting between up-and down-spin electrons in a singlet superconductor. In the absence of disorder, the superconducting order parameter has a periodic spatial structure, with periodicity determined by the Zeeman splitting. Using the Bogoliubov-de Gennes (BdG) approach, we investigate the spatial profiles of the order parameters of FFLO states in a two-dimensional s-wave superconductors with nonmagnetic impurities. The FFLO state is found to survive under moderate disorder strength, and the order parameter structure remains approximately periodic. The actual structure of the order parameter depends on not only the Zeeman field, but also the disorder strength and in particular the specific disorder configuration.

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Section: Discussionsupporting

confidence: 83%

Fulde-Ferrell-Larkin-Ovchinnikov state in disordereds-wave superconductors

Cui

Yang

2008

Phys. Rev. B

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“…The substrate granularity results in disordered superconducting films, where the localization of charge carriers by Coulomb interaction and the corresponding enhancement of quantum fluctuations of the phase of the superconductor order parameter induces the superconductor-insulator transition. 13 Lowering the baking and deposition temperature leads to a dramatic improvement of the surface quality and superconducting properties. Figure 1͑c͒ shows the AFM images of a 4.5 nm NbN film deposited at 350°C, after a ͑200°C for 12 h, 350°C for 30 min͒ baking sequence.…”

Section: Nanowire Superconducting Single-photon Detectors On Gaas Formentioning

confidence: 99%

Nanowire superconducting single-photon detectors on GaAs for integrated quantum photonic applications

Gaggero

Nejad

Marsili

et al. 2010

Applied Physics Letters

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We demonstrate efficient nanowire superconducting single photon detectors (SSPDs) based on NbN thin films grown on GaAs. NbN films ranging from 3 to 5 nm in thickness have been deposited by dc magnetron sputtering on GaAs substrates at 350 °C. These films show superconducting properties comparable to similar films grown on sapphire and MgO. In order to demonstrate the potential for monolithic integration, SSPDs were fabricated and measured on GaAs/AlAs Bragg mirrors, showing a clear cavity enhancement, with a peak quantum efficiency of 18.3% at λ=1300 nm and T=4.2 K.

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“…Moreover, understanding superconductivity in thin films is expected to clarify the behavior of resistance in thin metallic films in general. Likewise, it has even been suggested that the superconductivity-disorder interplay in thin films is the key to understanding high-T c superconductivity [4]. Therefore, it is the goal of this paper to demonstrate a universal behavior for T c in thin films as a function of both d and R s .…”

mentioning

confidence: 99%

“…Because superconductivity relies on a collective electron behavior, the onset of superconductivity occurs when the number of participating electrons is just enough to be considered collective, i.e., at the nanoscale [2][3][4][5]. Thus, it is known that the superconductivity-disorder interplay varies in thin films and is effectively tuned with the film thickness (d) or with the disorder in the system, which is represented by sheet resistance of the film at the normal state (R s ) [6][7][8][9][10].…”

mentioning

confidence: 99%

Universal scaling of the critical temperature for thin films near the superconducting-to-insulating transition

et al. 2014

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Thin superconducting films form a unique platform for geometrically confined, strongly interacting electrons. They allow an inherent competition between disorder and superconductivity, which in turn enables the intriguing superconducting-to-insulating transition and is believed to facilitate the comprehension of high-T c superconductivity. Furthermore, understanding thin film superconductivity is technologically essential, e.g., for photodetectors and quantum computers. Consequently, the absence of established universal relationships between critical temperature (T c ), film thickness (d), and sheet resistance (R s ) hinders both our understanding of the onset of the superconductivity and the development of miniaturized superconducting devices. We report that in thin films, superconductivity scales as dT c (R s ). We demonstrated this scaling by analyzing the data published over the past 46 years for different materials (and facilitated this database for further analysis). Moreover, we experimentally confirmed the discovered scaling for NbN films, quantified it with a power law, explored its possible origin, and demonstrated its usefulness for nanometer-length-scale superconducting film-based devices. Relationships between low-temperature and normal-state properties are crucial for understanding superconductivity. For instance, the Bardeen-Cooper-Schrieffer theory (BCS) successfully associates the normal-to-superconducting transition temperature, T c , with material parameters, such as the Debye temperature ( D ) and the density of states at the Fermi level [N (0)]. Hence, the BCS model allows us to infer superconducting characteristics (i.e., T c ) from properties measured at higher temperatures [1]. In the BCS framework, superconductivity occurs when attractive phonon-mediated electron-electron interactions overcome the Coulomb repulsion, giving rise to paired electrons (Cooper pairs) with a binding energy gap:. Moreover, within a superconductor, all Cooper pairs are coupled, giving rise to a collective electron interaction. Such a collective state is described by a complex global order parameter with real amplitude ( ) and phase (ϕ): = e iϕ .Because superconductivity relies on a collective electron behavior, the onset of superconductivity occurs when the number of participating electrons is just enough to be considered collective, i.e., at the nanoscale [2-5]. Thus, it is known that the superconductivity-disorder interplay varies in thin films and is effectively tuned with the film thickness (d) or with the disorder in the system, which is represented by sheet resistance of the film at the normal state (R s ) [6][7][8][9][10]. The mechanism of superconductivity in thin films has been investigated since the 1930s [6] increase in T c with decreasing thickness in aluminum films in a study that pioneered the currently ongoing research of thin superconducting films. This enhancement of T c , which is still not completely understood, was later confirmed by Strongin et al. [12], who also reported the more common be...

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Nature of the superconductor–insulator transition in disordered superconductors

Cited by 365 publications

References 33 publications

Fulde-Ferrell-Larkin-Ovchinnikov state in disordereds-wave superconductors

Fulde-Ferrell-Larkin-Ovchinnikov state in disordereds-wave superconductors

Nanowire superconducting single-photon detectors on GaAs for integrated quantum photonic applications

Universal scaling of the critical temperature for thin films near the superconducting-to-insulating transition

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