Quantum transport through carbon nanotubes: Proximity-induced and intrinsic superconductivity

Kasumov, A.; Kociak, Mathieu; Ferrier, M.; Deblock, R.; Guéron, S.; Reulet, Bertrand; Khodos, I. I.; Stéphan, Odile; Bouchiat, H.

doi:10.1103/physrevb.68.214521

Cited by 92 publications

(125 citation statements)

References 66 publications

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“…Second, even if the CNTs can have superconducting tendencies, the manifestation of superconductivity should be quenched by the long wavelength thermal fluctuations as dictated by the Hohenberg-Mermin Theorem for 1D systems, 11,12 as well as by the competing mechanism of the Peierls distortion that favors a semiconducting ground state. 13 Thus in spite of the theoretical prediction that small CNTs can be potential superconductors, owing to the curvature effect that opens the electron-phonon interaction channels, 14 early experimental results reported for different CNT systems [15][16][17][18] were greeted with skepticism. Other than the above-stated reasons, this is because only three groups have observed superconductivity in carbon nanotubes, 15,17,18 and even for these three groups no consistent sets of data, which should comprise electrical, magnetic, and thermal specific heat measurements, were obtained until recently.…”

Section: Introductionmentioning

confidence: 99%

Superconductivity in 4-Angstrom carbon nanotubes—a short review

et al. 2012

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We give an up-to-date review of the superconducting phenomena in 4-Angstrom carbon nanotubes embedded in aligned linear pores of the AlPO 4 -5 (AFI) zeolite, first discovered in 2001 as a fluctuation Meissner effect. With the introduction of a new approach to sample synthesis around 2007, new data confirming the superconductivity have been obtained. These comprise electrical, specific heat, and magnetic measurements which together yield a consistent yet complex physical picture of the superconducting state, largely owing to the one-dimensional (1D) nature of the 4-Angstrom carbon nanotubes. For the electrical transport characteristics, two types of superconducting resistive behaviors were reproducibly observed in different samples. The first type is the quasi 1D fluctuation superconductivity that exhibits a smooth resistance drop with decreasing temperature, initiating at 15 K. At low temperatures the differential resistance also shows a smooth increase with increasing bias current (voltage). Both are unaffected by an applied magnetic field up to 11 Tesla. These manifestations are shown to be consistent with those of a quasi 1D superconductor with thermally activated phase slips as predicted by the Langer-Ambegaokar-McCumber-Halperin (LAMH) theory. The second type is the quasi 1D to 3D superconducting crossover transition, which was observed to initiate at 15 K with a slow resistance decrease switching to a sharp order of magnitude drop at $7.5 K. The latter exhibits anisotropic magnetic field dependence and is attributed to a Berezinskii-Kosterlitz-Thouless (BKT)-like transition that establishes quasi-long-range order in the plane transverse to the c-axis of the aligned nanotubes, thereby mediating a 1D to 3D crossover. The electrical data are complemented by magnetic and thermal specific heat bulk measurements. By using both the SQUID VSM and the magnetic torque technique, the onset of diamagnetism was observed to occur at $15 K, with a rapid increase of the diamagnetic moment below $7 K. The zero-field-cooled and field-cooled branches deviated from each other below 7 K, indicating the establishment of a 3D Meissner state with macroscopic phase coherence. The superconductivity is further supported by the specific heat measurements, which show an anomaly with onset at 15 K and a peak at 11-12 K. In the 3D superconducting state, the nanotube arrays constitute a type-II anisotropic superconductor with H c1 z 60 to 150 Oe, coherence length x z 5 to 15 nm, London penetration length l z 1.5 mm, and Ginzburg-Landau k z 100. We give a physical interpretation to the observed phenomena and note the challenges and prospects ahead.

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Section: Introductionmentioning

confidence: 99%

Superconductivity in 4-Angstrom carbon nanotubes—a short review

et al. 2012

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“…[1][2][3] By using superconducting metals as electrodes, a significant increase of spectroscopic resolution due to the sharp peaks at the gap edges in the BCS density of states can be achieved. 4 Depending on the coupling strength between the carbon nanotube and its leads, the nanotube can act as a Josephson weak link, and proximity-induced supercurrent can flow through the quantum dot.…”

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confidence: 99%

“…4 Depending on the coupling strength between the carbon nanotube and its leads, the nanotube can act as a Josephson weak link, and proximity-induced supercurrent can flow through the quantum dot. 3,[5][6][7] The supercurrent is carried by Andreev bound states, whose presence is revealed by peculiar subgap features. [8][9][10][11][12] By fabricating the contacts from sputtered Nb, they can remain superconducting up to a critical temperature T c = 8.5 K and a correspondingly large critical magnetic field B c .…”

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confidence: 99%

Subgap spectroscopy of thermally excited quasiparticles in a Nb-contacted carbon nanotube quantum dot

et al. 2014

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We present electronic transport measurements of a single wall carbon nanotube quantum dot coupled to Nb superconducting contacts. For temperatures comparable to the superconducting gap peculiar transport features are observed inside the Coulomb blockade and superconducting energy gap regions. The observed temperature dependence can be explained in terms of sequential tunneling processes involving thermally excited quasiparticles. In particular, these new channels give rise to two unusual conductance peaks at zero bias in the vicinity of the charge degeneracy point and allow to determine the degeneracy of the ground states involved in transport. The measurements are in good agreement with model calculations.

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“…6 Moreover, superconducting transitions have been measured in ropes suspended between metallic, nonsuperconducting electrodes. 7,8 These observations imply the existence of a regime with a relevant attractive component in the electron-electron interaction, coming presumably from the exchange of phonons between electronic currents. 9 From a theoretical point of view, it is well-known that the Luttinger liquid regime may break down in the carbon nanotubes, due to a variety of low-temperature instabilities.…”

Section: Introductionmentioning

confidence: 99%

Coulomb screening and electronic instabilities of small-diameter (5,0) nanotubes

González

Perfetto

2005

Phys. Rev. B

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We investigate the instabilities that may lead to the breakdown of the Luttinger liquid in the small-diameter ͑5,0͒ nanotubes, paying attention to the competition between the effective interaction mediated by phonon exchange and the Coulomb interaction. We use bosonization methods to achieve an exact treatment of the Coulomb interaction at small momentum transfer, and apply next renormalization group methods to analyze the low-energy behavior of the electron system. This allows us to discern the growth of several response functions for charge-density-wave modulations and for superconducting instabilities with different order parameters. We show that, in the case of single nanotubes exposed to screening by external gates, the Luttinger liquid is unstable against the onset of a strong-coupling phase with very large charge-density-wave correlations. The temperature of crossover to the new phase depends crucially on the dielectric constant of the environment, ranging from T c ϳ 10 −4 K ͑at Ϸ 1͒ up to a value T c ϳ 10 2 K ͑reached from Ϸ 10͒. The physical picture is however different when we consider the case of a large array of nanotubes, in which there is a three-dimensional screening of the Coulomb interaction over distances much larger than the intertube separation. The electronic instability is then triggered by the divergence of one of the charge stiffnesses in the Luttinger liquid, implying a divergent compressibility and the appearance of a regime of phase separation into spatial regions with excess and defect of electron density.

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Quantum transport through carbon nanotubes: Proximity-induced and intrinsic superconductivity

Cited by 92 publications

References 66 publications

Superconductivity in 4-Angstrom carbon nanotubes—a short review

Superconductivity in 4-Angstrom carbon nanotubes—a short review

Subgap spectroscopy of thermally excited quasiparticles in a Nb-contacted carbon nanotube quantum dot

Coulomb screening and electronic instabilities of small-diameter (5,0) nanotubes

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