Superconducting characteristics of 4-Å carbon nanotube–zeolite composite

Lortz, Rolf; Zhang, Qiucen; Shi, Wu; Ye, Jiang Ting; Qiu, Chunyin; Wang, Zhe; He, Hongtao; Sheng, Ping; Qian, Tiezheng; Tang, Zikang; Wang, Ning; Zhang, Xixiang; Wang, Jiannong; Chan, Che Ting

doi:10.1073/pnas.0813162106

Cited by 60 publications

(75 citation statements)

References 27 publications

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“…The proportion of the 550 cm À1 peak (delineated by green bars) is seen to be $10% of the G-band signal, which is significantly higher than the $5% average RBM signals observed in samples fabricated by the old process (delineated by red bars). 19 An important feature of the statistical result is that for the new process, the RBM/G values are tightly distributed around the average, with no zero values. This is a clear indication of sample uniformity, in contrast to the non-uniformity of the old process in which $25% of the samples display no RBM signal or very poor RBM signals.…”

Section: New Approach To Sample Synthesismentioning

confidence: 99%

“…19 As a measurement of the heat capacity probes the entire volume of the sample, the detection of the characteristic specific-heat anomaly associated with the superconducting transition is considered a definitive bulk proof of superconductivity. The embedded CNTs represent only a tiny volume fraction of the composite material.…”

Section: Thermal Specific Heat Characteristicsmentioning

confidence: 99%

“…19 Instead of the original TPA, continuously flowing ethylene gas is externally introduced into the vacated AFI channels as the carbon source to synthesize the 4-Angstrom SWNTs. This approach ensures sufficient carbon source for the formation of CNTs uniformly inside the AFI channels.…”

Section: New Approach To Sample Synthesismentioning

confidence: 99%

“…The physical picture that emerges is a fairly complex one showing fluctuating quasi 1D superconducting behavior initiating at 15 K with a crossover to 3D superconductivity via coupling between the aligned nanotubes 20 at around 6-7.5 K. This picture is supported by the consistency of the electrical, magnetic, and thermal data. [19][20][21] In the 3D superconducting state, the nanotube arrays constitute a type-II, anisotropic superconductor with a H c1 ¼ 60-150 Oe, a coherence length x z 5 to 15 nm, a London penetration length l z 1.5 mm, and a Ginzburg-Landau k z 100.…”

Section: Introductionmentioning

confidence: 99%

“…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. [19][20][21] This review serves to gather all the experimental evidence for superconductivity in one type of carbon nanotube-the 4-Angstrom single-walled carbon nanotubes (SWNTs) embedded in AlPO 4 -5 zeolite template. The experimental data offer some answers to how the superconductivity can appear in spite of the various above-stated obstacles.…”

Section: Introductionmentioning

confidence: 99%

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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: New Approach To Sample Synthesismentioning

confidence: 99%

Section: Thermal Specific Heat Characteristicsmentioning

confidence: 99%

Section: New Approach To Sample Synthesismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Superconductivity in 4-Angstrom carbon nanotubes—a short review

et al. 2012

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1D Superconductivity in a Related System

Altomare

Chang

2013

One‐Dimensional Superconductivity in Nanowires

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1D goes 2D: A Berezinskii–Kosterlitz–Thouless transition in superconducting arrays of 4‐Angstrom carbon nanotubes

Wang

Shi

Xie

et al. 2010

Physica Status Solidi (b)

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We report superconducting resistive transition characteristics for array(s) of coupled 4-Angstrom single wall carbon nanotubes embedded in aluminophosphate-five zeolite. The transition was observed to initiate at 15 K with a slow resistance decrease switching to a sharp, order of magnitude drop between 7.5 and 6.0 K with strong (anisotropic) magnetic field dependence. Both the sharp resistance drop and its attendant nonlinear IV characteristics are consistent with the manifestations of a Berezinskii-Kosterlitz-Thouless transition that establishes quasi long range order in the plane transverse to the c-axis of the nanotubes, leading to an inhomogeneous system comprising 3D superconducting regions connected by weak links. Global coherence is established at below 5 K with the appearance of a well-defined supercurrent gap/low resistance region at 2 K.Superconductivity in carbon nanotubes has been controversial because carbon is not known to be a superconducting element, and if there is indeed superconducting tendency in carbon nanotubes [1] (the large curvature of small carbon nanotubes can potentially open electronphonon couplings that are absent in the graphene sheet, thereby enhancing the prospect for superconductivity), its manifestation could be quenched by long wavelength thermal fluctuations as well as by the Peierls distortion that favors an insulating ground state. In this context the earlier report on the Meissner effect in 4-Angstrom carbon nanotube-zeolite composites [2] and the more recent observation of their superconducting specific heat signals [3] have only deepened the mystery on the specific manner in which the nanotube superconductivity comes into being, and on whether there can be a sharp superconducting resistive transition that is usually taken to be the hallmark of a superconductor. Here we show that by devising strategy to make surface electrical contacts to the samples that are separated by only 100 nm, reliable and repeatable observations of the superconducting resistive transition can be obtained. The physical picture which emerges is that of a coupled Josephson array consisting of aligned nanotubes crossing over from an individually fluctuating 1D system to a coherent 3D superconductor, mediated by a BerezinkiiKosterlitz-Thouless (BKT) transition [4,5] which establishes quasi long range order in the transverse plane perpendicular to the c-axis of the nanotubes. The attainment of overall coherence across the measuring electrodes (denoted as global coherence in this work) is seen at 5 K and below, evidenced by the appearance of a well-defined (differential resistance) supercurrent gap/low resistance region at 2 K. Figure 1 shows both a cartoon picture (Fig. 1a) of the aluminophosphate-five (AFI) zeolite crystal with the fourprobe contact geometry, as well as a scanning electron microscope (SEM) image of an actual sample (Fig. 1b). Here the sample was prepared by first cutting two troughs in an AFI crystal (50 Â 50 Â 500 mm 3 ) with focused ion beam (FIB, Seiko SMI2050), separated by a 5 mm ...

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Superconducting characteristics of 4-Å carbon nanotube–zeolite composite

Cited by 60 publications

References 27 publications

Superconductivity in 4-Angstrom carbon nanotubes—a short review

Superconductivity in 4-Angstrom carbon nanotubes—a short review

1D Superconductivity in a Related System

1D goes 2D: A Berezinskii–Kosterlitz–Thouless transition in superconducting arrays of 4‐Angstrom carbon nanotubes

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