Superconducting Pair Correlations in an Amorphous Insulating Nanohoneycomb Film

Stewart, M. D.; Yin, Aijun; Xu, Jimmy; Valles, James M.

doi:10.1126/science.1149587

Cited by 153 publications

(191 citation statements)

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“…Near the IST, these insulating NHC a-Bi films exhibit the characteristic transport signatures of the CPI phase. 18,19 Moreover, the insulators are confirmed to contain Cooper pairs through Little-Parks-like magnetoresistance oscillations induced by the hole array. 18 How the NHC substrates induce the formation of the CPI state in these films is the primary focus of this paper.…”

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confidence: 99%

“…T 0 decreases continuously on approaching the IST (also shown in Refs. 18,19,23 ). We define the critical thickness for the IST, d IST , as the thickness at which T 0 linearly extrapolates to zero.…”

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confidence: 99%

“…The exponential rise indicates thermally activated transport, R(T ) ∝ e T0 T . 18 For all the ISTs, the normal state sheet conductance, G(8K) = 1 R(8K) grows linearly with deposited film thickness, d…”

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confidence: 99%

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Cooper-pair insulator phase in superconducting amorphous Bi films induced by nanometer-scale thickness variations

et al. 2011

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Cooper-pair insulator phase in superconducting amorphous Bi films induced by nanometer-scale thickness variations

et al. 2011

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“…Early work focused on the most easily measurable quantity, the DC conductivity. [1][2][3][6][7][8][9][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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“…Novel phenomena, such as hc∕e as opposed to the hc∕2e Little-Parks oscillations as the size of the loop is reduced (10,11) and the occurrence of superconductivity in the smallest doubly connected samples, the thinnest carbon nanotubes (12), may be expected. New experimental techniques capable of probing these fluctuations were developed (13,14). Therefore, similar to singly connected mesoscopic superconductors in which some spectacular physical phenomena were found (15)(16)(17), ultrasmall doubly connected superconductors are likely to grow into a fertile testing ground for fundamental studies of superconductivity.…”

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Manipulating superconducting fluctuations by the Little–Parks–de Gennes effect in ultrasmall Al loops

Staley

Liu

2012

Proc. Natl. Acad. Sci. U.S.A.

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The destruction of superconducting phase coherence by quantum fluctuations and the control of these fluctuations are a problem of long-standing interest, with recent impetus provided by the relevance of these issues to the pursuit of high temperature superconductivity. Building on the work of Little and Parks, de Gennes predicted more than three decades ago that superconductivity could be destroyed near half-integer-flux quanta in ultrasmall loops, resulting in a destructive regime, and restored by adding a superconducting side branch, which does not affect the flux quantization condition. We report the experimental observation of this LittleParks-de Gennes effect in Al loops prepared by advanced e-beam lithography. We show that the effect can be used to restore the lost phase coherence by employing side branches.nanoscale superconductivity | phase coherrence manipulation T he problem of superconducting fluctuations, including the existence of a many-body state composed of fluctuating, phaseincoherent Cooper pairs, has been at the forefront of superconductivity research for decades (1). The fluctuating Cooper pair state, which may emerge when the global superconducting phase coherence is destroyed by strong disorder, Coulomb repulsive interaction, or magnetic field, may have been realized in the pseudogap phase of the high T c cuprate materials. If the fluctuations in such a state could be suppressed and global phase coherence built through engineering means, very high temperature superconductivity could be obtained (2). A similar state of fluctuating Cooper pairs, controllable through geometry and applied magnetic flux, is found in doubly connected ultrasmall superconductors (3-5). Recent theoretical studies have produced some detailed predictions on the nature of the thermal and quantum superconducting fluctuations in this state (6-9). Novel phenomena, such as hc∕e as opposed to the hc∕2e Little-Parks oscillations as the size of the loop is reduced (10, 11) and the occurrence of superconductivity in the smallest doubly connected samples, the thinnest carbon nanotubes (12), may be expected. New experimental techniques capable of probing these fluctuations were developed (13,14). Therefore, similar to singly connected mesoscopic superconductors in which some spectacular physical phenomena were found (15-17), ultrasmall doubly connected superconductors are likely to grow into a fertile testing ground for fundamental studies of superconductivity.The fluxoid quantization in a thin, doubly connected superconductor requires that an applied flux (Φ) threading the superconductor, produce a superfluid velocity v s ∼ ð1∕CÞðn − Φ∕Φ 0 Þ, where C is the circumference of the loop, n is an integer that minimizes v s , and Φ 0 ð¼ hc∕2eÞ is the flux quantum. The periodic modulation of v s , which reaches a maximum at half-integer-flux quanta, leads to the well-known Little-Parks oscillations in T c (18,19). Based on a Ginzburg-Landau (G-L) theory, de Gennes made a prediction in 1981 (3) that the T c oscillation amplitude could ...

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Superconducting Pair Correlations in an Amorphous Insulating Nanohoneycomb Film

Cited by 153 publications

References 28 publications

Cooper-pair insulator phase in superconducting amorphous Bi films induced by nanometer-scale thickness variations

Cooper-pair insulator phase in superconducting amorphous Bi films induced by nanometer-scale thickness variations

Divergence of dynamical conductivity at certain percolative superconductor-insulator transitions

Manipulating superconducting fluctuations by the Little–Parks–de Gennes effect in ultrasmall Al loops

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