Localization of preformed Cooper pairs in disordered superconductors

Sacépé, Benjamin; Dubouchet, Thomas; Chapelier, Claude; Sanquer, M.; Ovadia, M.; Shahar, D.; Фейгельман, М. В.; Ioffe, L. B.

doi:10.1038/nphys1892

Cited by 362 publications

(363 citation statements)

References 45 publications

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“…Following this relationship, the experiments on the B-SIT and the experiments tuning the carrier density form a dual set of experiments. Interestingly, this analogy implies that the disorder-driven SIT at B = 0 must have a different mechanism for the insulating state; a distinction that cannot be made from experiments: Transport and scanning tunnelling experiments [24][25][26] as well as microscopic model calculations 27,28 suggest that Cooper pairs persist also in the disorder-driven insulating state.…”

Section: T0/2tmentioning

confidence: 99%

Duality symmetry and its breakdown in the vicinity of the superconductor–insulator transition

et al. 2013

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The superconductor-insulator transition (SIT) is an accessible quantum phase transition 1,2 that is observed in a number of systems and can be driven by various experimental means 3-9 . A central outstanding issue regards the physical nature of the insulating phase terminating superconductivity 10 . Theoretical advances led to the proposition that this insulator is a new state of matter, termed a superinsulator 11,12 , because its properties can be inferred from the superconductor by invoking duality symmetry 13 . Here we report on the observation of duality symmetry near the magnetic-field-driven SIT in amorphous indium oxide. However, we show that the symmetry is broken by the emergence of the strong insulating state at low temperature.For the magnetic-field-driven SIT (B-SIT) in disordered films, the concept of vortex-charge duality was investigated in ref. 14, using the dirty boson model. In the superconductor, Cooper pairs are condensed into a superfluid at low temperature (T ) values leading to a zero resistivity (ρ) state, with vortices as bosonic excitations introducing dissipation and causing finite ρ. According to the duality concept, in the insulating state, vortices are condensed in a collective mode with zero conductivity (σ ), and the Cooper pairs are the bosonic excitation contributing to a finite σ .The vortex-charge duality has also been applied to the analysis of Josephson junction arrays 15,16 , which are often used as a model system for the SIT in disordered films 11,12,17 . In these systems the insulating state is commonly ascribed to a Coulomb blockade of superconducting islands. Duality is also applied to many other systems, for example, boson duality in two-dimensional electron gases 18 . Recently, evidence for the vortex-charge duality near a SIT was found in LaAlO 3 /SrTiO 3 interfaces 13 .Here, we experimentally investigate the duality symmetry across the B-SIT. We apply a duality transformation relating states within the superconductor to states in the B-driven insulator. We observe vortex-charge duality symmetry that holds up to one order of magnitude in B, T and ρ. The new aspect of this work is that we find systematic deviations from duality symmetry that originate in the B-induced magnetoresistance (ρ(B)) peak 5 . These deviations are qualitatively different at low and high T , as will be shown in detail below.In Fig. 1 we present ρ(B) isotherms obtained from sample RAM005b, which is superconducting at B = 0 with T c = 1.3 K. For all T values where reliable Ohmic data could be collected ρ increases with B until it reaches a T -dependent peak at B peak between 8.5-9.7 T. We restrict ourselves to T > 0.15 K because in the insulating phase, at T < 0.15 K, severe bi-stability of the electron T develops 19 , resulting in strongly nonlinear I -V , that prevented reliable measurements of ρ.The isotherms exhibit a weakly T -dependent crossing point close to h/(2e) 2 , where h is Planck's constant and 2e is the charge

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Section: T0/2tmentioning

confidence: 99%

Duality symmetry and its breakdown in the vicinity of the superconductor–insulator transition

et al. 2013

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“…Early work focused on the most easily measurable quantity, the DC conductivity. [1-3, 6-10] Recently, due to the availability of local scanning probes, attention has turned to the tunneling behavior [11][12][13][14][15]. In the case of the disorder-tuned SIT [15], it has become clear that the SIT is ultimately due to a bosonic mechanism [16] rather than a fermionic one [17].…”

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confidence: 99%

Divergence of dynamical conductivity at certain percolative superconductor-insulator transitions

Loh¹,

Dhakal²,

Neis³

et al. 2014

J. Phys.: Condens. Matter

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Random inductor-capacitor (LC) networks can exhibit percolative superconductor-insulator transitions (SITs). We use a simple and efficient algorithm to compute the dynamical conductivity σ(ω, p) of one type of LC network on large (4000 × 4000) square lattices, where δ = p − pc is the tuning parameter for the SIT. We confirm that the conductivity obeys a scaling form, so that the characteristic frequency scales as Ω ∝ |δ| νz with νz ≈ 1.91, the superfluid stiffness scales as Υ ∝ |δ| t with t ≈ 1.3, and the electric susceptibility scales as χE ∝ |δ| −s with s = 2νz − t ≈ 2.52. In the insulating state, the low-frequency dissipative conductivity is exponentially small, whereas in the superconductor, it is linear in frequency. The sign of Im σ(ω) at small ω changes across the SIT. Most importantly, we find that right at the SIT Re σ(ω) ∝ ω t/νz−1 ∝ ω −0.32 , so that the conductivity diverges in the DC limit, in contrast with most other classical and quantum models of SITs. [4,5]. As a quantum phase transition occurring at zero temperature, this superconductor-insulator transition (SIT) has attracted much interest. Early work focused on the most easily measurable quantity, the DC conductivity.[1-3, 6-10] Recently, due to the availability of local scanning probes, attention has turned to the tunneling behavior [11][12][13][14][15]. In the case of the disorder-tuned SIT [15], it has become clear that the SIT is ultimately due to a bosonic mechanism [16] rather than a fermionic one [17]. The last step towards a full characterization of the SIT is to develop an understanding of the behavior of the AC conductivity. This is a powerful probe of fluctuations on both long and short length and time scales, and it is of great interest especially as recent technological developments begin to open up more windows of the electromagnetic spectrum for measurement [18][19][20][21].One of the most important questions concerns the AC conductivity in the "collisionless DC" limit [22,23] [52], σ * = lim ω→0 lim T →0 σ(ω, T ). This has been the subject of a large body of work, including analytical arguments involving charge-vortex duality arguments, quantum Monte Carlo calculations in various representations, and experiments [1,4,16,23,[25][26][27][28][29][30][31][32]. It is often claimed that at the SIT σ * is finite and takes a universal value of the order of σ Q = 4e 2 /h, but there are large discrepancies between the "universal" values from various studies, and it is not clear whether there really is a universal value.

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“…4): at T ¼ T c (local) the superconducting gap opens locally in the grains that together form a 3D system with a small degree of disorder. Granularity-correlated disorder could lead to the localization of individual bosonic droplets (islands of Cooper pairs) [19,[27][28][29] that also absorb the fermions around the Fermi level E F , thus reducing the normal single quasiparticle conductivity N ¼ 1= N . Localized bosonic islands, absorbing ''metallic'' fermions [ Fig.…”

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Metal–Bosonic Insulator–Superconductor Transition in Boron-Doped Granular Diamond

et al. 2013

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In a variety of superconductors, mostly in two-dimensional (2D) and one-dimensional (1D) systems, the resistive superconducting transition RðTÞ demonstrates in many cases an anomalous narrow RðTÞ peak just preceding the onset of the superconducting state R ¼ 0 at T c . The amplitude of this RðTÞ peak in 1D and 2D systems ranges from a few up to several hundred percent. In three-dimensional (3D) systems, however, the RðTÞ peak close to T c is rarely observed, and it reaches only a few percent in amplitude. Here we report on the observation of a giant ($ 1600%) and very narrow ( $ 1 K) resistance peak preceding the onset of superconductivity in heavily boron-doped diamond. This anomalous RðTÞ peak in a 3D system is interpreted in the framework of an empirical model based on the metal-bosonic insulator-superconductor transitions induced by a granularity-correlated disorder in heavily doped diamond. DOI: 10.1103/PhysRevLett.110.077001 PACS numbers: 74.70.Wz, 71.30.+h, 74.25.Àq, 74.62.En Since the 1950s [1], a puzzling anomalous increase of resistance, RðTÞ, preceding the superconducting transition, has been reported in some superconducting systems situated not yet in the vicinity of the insulator-metal transition (IMT) with relatively low residual resistance. At first, the increase was only observed at the level of a few percent. Later on, in thin films [2][3][4] and 1D whiskers and wires [5,6], similar effects were also found, with a considerably higher amplitude of the RðTÞ anomaly: 16% and 160%. With the discovery of quasi-2D cuprates, the RðTÞ peak around T c was also reported for these lowdimensional materials, such as NdCeCuO [7], BiSrCaCuO [8,9], and LaSrCuO [10,11], with the peak amplitude reaching 400%-700%. In 2D and 1D microstructures [6,[12][13][14][15][16], made from conventional superconducting materials (mostly Al), a narrow resistance peak close to T c was also observed, with the peak amplitude reaching the 400% level.Different models were used to explain the nature of the anomalous RðTÞ peak: normal-metal-superconductor boundaries, disorder and fluctuations, vortex dynamics and Josephson coupling in layered systems, charge imbalance, and competition between superconducting and insulating states in 2D systems [1,2,4,6,8,[12][13][14]16,17].All these observations of the RðTÞ peak around T c and the corresponding models and theories, formulated to explain the corresponding experimental data, are very much linked to the reduced dimensionality of the investigated systems: 2D or/and 1D. We have found reports on the RðTÞ peak for 3D-like metallic Cu-Zr glasses only in a couple of previous publications [17,18] with a quite small RðTÞ peak amplitude-less than 3%. We present here our novel observations of the giant RðTÞ peak in 3D boron-doped granular diamond, which are very different from previously reported data in the following important aspects.First, the effect has a giant amplitude: the peak resistance value exceeds the residual resistance close to T c by 550%-1600%, which is a much higher value tha...

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Localization of preformed Cooper pairs in disordered superconductors

Cited by 362 publications

References 45 publications

Duality symmetry and its breakdown in the vicinity of the superconductor–insulator transition

Duality symmetry and its breakdown in the vicinity of the superconductor–insulator transition

Divergence of dynamical conductivity at certain percolative superconductor-insulator transitions

Metal–Bosonic Insulator–Superconductor Transition in Boron-Doped Granular Diamond

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