Observation of surface superconductivity and direct vortex imaging of a Pb thin island with a scanning tunneling microscope

Ning, Yanxiao; Song, Can-Li; Guan, Zelei; C., X.; Chen, Xi; Jia, Jin; Xue, Qi Kun

doi:10.1209/0295-5075/85/27004

Cited by 24 publications

(24 citation statements)

References 29 publications

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“…2f). Such a relation has been reported in systems such as Bi 2 Sr 2 CaCu 2 O 8 þ d overdoped with intercalating HgBr 2 molecules 36 and in nanosized Pb islands on a silicon wafer 37 .…”

Section: Resultssupporting

confidence: 55%

Anomalous magnetoresistance in the spinel superconductor LiTi2O4

Jin

Zhang

et al. 2015

Nat Commun

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LiTi 2 O 4 is a unique compound in that it is the only known spinel oxide superconductor. The lack of high quality single crystals has thus far prevented systematic investigations of its transport properties. Here we report a careful study of transport and tunnelling spectroscopy in epitaxial LiTi 2 O 4 thin films. An unusual magnetoresistance is observed which changes from nearly isotropic negative to prominently anisotropic positive as the temperature is decreased. We present evidence that shows that the negative magnetoresistance likely stems from the suppression of local spin fluctuations or spin-orbit scattering centres. The positive magnetoresistance suggests the presence of an orbital-related state, also supported by the fact that the superconducting energy gap decreases as a quadratic function of magnetic field. These observations indicate that the spin-orbital fluctuations play an important role in LiTi 2 O 4 in a manner similar to high-temperature superconductors.

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“…2f). Such a relation has been reported in systems such as Bi 2 Sr 2 CaCu 2 O 8 þ d overdoped with intercalating HgBr 2 molecules 36 and in nanosized Pb islands on a silicon wafer 37 .…”

Section: Resultssupporting

confidence: 55%

Anomalous magnetoresistance in the spinel superconductor LiTi2O4

Jin

Zhang

et al. 2015

Nat Commun

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“…[246] developed a method to fabricate atomically flat superconducting surfaces in thin films and map the vortex distribution. Vortex nucleation has been traced in single crystalline thin film and in nanosized Pb islands [68][69][70][71][72][73][74][75]. In those cases, pinning mechanisms are probably related to impurities, step edges or proximity effect Figure 26.…”

Section: 27mentioning

confidence: 99%

Imaging superconducting vortex cores and lattices with a scanning tunneling microscope

Suderow¹,

Guillamón²,

Rodrigo³

et al. 2014

Supercond. Sci. Technol.

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Abstract. The observation of vortices in superconductors was a major breakthrough in developing the conceptual background for superconducting applications. Each vortex carries a flux quantum, and the magnetic field radially decreases from the center. Techniques used to make magnetic field maps, such as magnetic decoration, give vortex lattice images in a variety of systems. However, strong type II superconductors allow penetration of the magnetic field over large distances, of order of the magnetic penetration depth λ. Superconductivity survives up to magnetic fields where, for imaging purposes, there is no magnetic contrast at all. Static and dynamic properties of vortices are largely unknown at such high magnetic fields. Reciprocal space studies using neutron scattering have been employed to obtain insight into the collective behavior. But the microscopic details of vortex arrangements and their motion remain difficult to obtain. Direct real space visualization can be made using scanning tunneling microscopy and spectroscopy (STM/S). Instead of using magnetic contrast, the electronic density of states describes spatial variations of the quasiparticle and pair wavefunction properties. These are of order of the superconducting coherence length ξ, which is much smaller than λ. In principle, individual vortices can be imaged using STM up to the upper critical field where vortex cores, of size ξ, overlap. In this review, we describe recent advances in vortex imaging made with scanning tunneling microscopy and spectroscopy. We introduce the technique and discuss vortex images which reveal the influence of the Fermi surface distribution of the superconducting gap on the internal structure of vortices, the collective behavior of the lattice in different materials and conditions, and the observation of vortex lattice melting. We consider challenging lines of work, which include imaging vortices in nanostructures, multiband and heavy fermion superconductors, single layers and van-der-Waals crystals, studying current driven dynamics and the liquid vortex phases.

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“…Therefore, a linear dependence of ZBC vs H is expected, as observed recently in Pb islands. 24 However, it is not the case here. We observed a linear dependence of the ͑ZBC͒ 1/2 , not ZBC, with H above 0.18 T and a near plateau below 0.18 T, as shown in Fig.…”

mentioning

confidence: 80%

“…The latest progress in this aspect includes the study of quantum size effects in two-dimensional ͑2D͒ thin films and nanoislands of Pb. [20][21][22][23][24][25][26] Here, we report the atomic scale-dependent superconducting properties of the Pb nanoribbons by using STM/STS.…”

mentioning

confidence: 99%

Sample-size dependence of the superconducting transition of ribbon-shaped Pb nanocrystals studied by scanning tunneling spectroscopy

et al. 2010

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We have systematically investigated the superconductivity of single crystalline Pb nanoribbons grown on Si substrates by using low temperature scanning tunneling microscopy/spectroscopy. Superconductivity transition is observed in the nanoribbons with a width ϳ10 nm and a thickness of 2.9 nm. By studying the width dependence of the superconducting parameters T c and H c 2 , a dimensional crossover between two dimensions and one dimension is identified.When the diameter of superconducting nanowires is comparable to or smaller than the superconducting coherence length, the superconductivity of the nanowires exhibits onedimensional ͑1D͒ or quasi-one-dimensional behaviors. This has attracted much attention due to both fundamental interest and potential applications. [1][2][3][4][5][6][7][8][9] In this regime, Cooper pairs are squeezed into a very small volume, their wave functions are strongly modified; thus, the quantum confinement effect in transverse dimensions on the superconducting order parameter becomes important. The thermal and quantum fluctuations of the superconducting order parameters 7 will play a dominating role and therefore suppress the superconductivity. 2 To address these issues, single crystalline nanowires with atomic level-controlled sizes 10-13 are required. However, the nanowires studied so far usually suffer from some uncertainties, such as the presence of disorder and defects. 10,11,[13][14][15][16][17][18] Particularly, precise size control of an individual superconductive nanowire and its transport measurement still remain a great technical challenge.Recently, we have developed a method by which highly ordered arrays of superlong Pb nanoribbons with atomic level-controlled thickness and width could be prepared on Si substrates by molecular beam epitaxy ͑MBE͒. The method employs a nanoscale template of the Al-decorated Si͑111͒ surfaces, where the width and thickness of the Pb nanoribbons are precisely controlled by the Al ͑less than 1 ML͒ and Pb coverages, respectively. 19 The superconductivity of such nanostructures can be studied in situ by a scanning tunneling microscope ͑STM͒ operated at low temperature and under magnetic field. The latest progress in this aspect includes the study of quantum size effects in two-dimensional ͑2D͒ thin films and nanoislands of Pb. 20-26 Here, we report the atomic scale-dependent superconducting properties of the Pb nanoribbons by using STM/STS.Our experiments were carried out in an ultrahigh vacuum ͑UHV͒ low temperature STM system combined with a MBE chamber ͑Unisoku USM-1300 and RHK SPM-1000͒. By simultaneously heating and pumping the low temperature insert, the STM samples can be maintained at a temperature range of 2.2-50 K by liquid 4 He cooling. A magnetic field up to 7 T can be applied along the direction perpendicular to the sample surface. After in situ preparation of nanoribbons on Si ͑111͒ substrate ͑As-doped, 1 -5 m⍀ cm͒ with a miscut of Ϯ0.3°in the MBE chamber, as described in the previous study, 19 the samples were transferred to the STM stage...

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Observation of surface superconductivity and direct vortex imaging of a Pb thin island with a scanning tunneling microscope

Cited by 24 publications

References 29 publications

Anomalous magnetoresistance in the spinel superconductor LiTi2O4

Anomalous magnetoresistance in the spinel superconductor LiTi2O4

Imaging superconducting vortex cores and lattices with a scanning tunneling microscope

Sample-size dependence of the superconducting transition of ribbon-shaped Pb nanocrystals studied by scanning tunneling spectroscopy

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