Imaging of a Vortex Lattice Transition in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>YNi</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi>B</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mi>C</mml:mi></mml:math>by Scanning Tunneling Spectroscopy

Sakata, Hideaki; Oosawa, Morimi; Мацуба, К.; Nishida, N.; Takeya, Hiroyuki; Hirata, Kazuto

doi:10.1103/physrevlett.84.1583

Cited by 85 publications

(59 citation statements)

References 16 publications

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“…In spite of intensive search with the x-y table, we were unable to find sufficiently flat zones to obtain atomic resolution. These results are similar to the observations made in other borocarbides [5].…”

supporting

confidence: 92%

“…The same low noise STM electronics was used on both setup but one had filters and the other none. In the unfiltered setup we find a fictitious finite conductance at zero bias and we need to introduce a broadening parameter Γ ≈ 0.3∆ [7], comparable to the 3 values obtained in previous works [6,5,14,15]. On the contrary, the curve measured with appropriate shielding can be accurately fitted to the conventional BCS expression, using the superconducting gap ∆ and the temperature T as the only fitting parameters.…”

supporting

confidence: 73%

“…To our knowledge, no previously published tunneling experiment is available in this compound. The tunneling experiments reported up to now in nonmagnetic compounds and the point contact spectroscopy data in magnetic compounds [6,5,14,15] have never shown a simple BCS density of states N BCS (E) and the conductance curves were all severely broadened. Therefore, the possible presence of low energy excitations as well as the form of the superconducting gap in the coexistence region were masked by extrinsic broadening.…”

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confidence: 99%

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Tunneling spectroscopy in the magnetic superconductorTmNi2B2C

et al. 2001

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We present new measurements about the tunneling conductance in the borocarbide superconductor TmNi 2 B 2 C. The results show a very good agreement with weak coupling BCS theory, without any lifetime broadening parameter, over the whole sample surface. We detect no particular change of the tunneling spectroscopy below 1.5K, when both the antiferromagnetic (AF) phase and the superconducting order coexist.

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supporting

confidence: 92%

supporting

confidence: 73%

mentioning

confidence: 99%

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Tunneling spectroscopy in the magnetic superconductorTmNi2B2C

et al. 2001

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“…2(a)]), but on the crystal axis. The observed change of the vortex lattice with the magnetic field is the same as those observed in the STS experiment 12) and the small angle neutron scattering experiment. 16) The dependences of N s ð0 meV; r; Þ ( ¼ 0 and 45 ) on the radial distance r are plotted in Fig.…”

supporting

confidence: 82%

“…The critical temperature T c was determined to be 15.6 K from dc magnetization measurement. The residual resistivity ratio RRR was 28.8, and the resistivity at T c was 1.2 m cm, while in our previous experiment, 12) the RRR of the sample was about 6. The mean free path ' of the present sample was calculated to be 70 nm from the RRR using the electronic density of states at the Fermi energy.…”

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confidence: 53%

First Observation of the Fourfold-symmetric and Quantum Regime Vortex Core in YNi₂B₂C by Scanning Tunneling Microscopy and Spectroscopy

et al. 2004

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The local quasi-particle density of states, N s ðE; rÞ, in the isolated vortex of YNi 2 B 2 C has been measured at 0.46 K by low-temperature scanning tunneling microscopy and spectroscopy. The vortex core is found to be fourfold-symmetric star-shaped in real space: Near E ¼ 0 meV, N s ðE; rÞ extends toward h100i (the a-axis) and has a peak at the center of the vortex core. With increasing energy, N s ðE; rÞ comes to extend toward h110i and the peak of N s ðE; rÞ splits into four peaks toward h110i. N s ðE; rÞ in the vortex core exhibits electron-hole asymmetry with the intensity, indicating the first observation of the vortex core in a quantum regime. Low-temperature scanning tunneling microscopy and spectroscopy (LT-STM/STS) is a powerful method for investigating the vortex state in type II superconductors; 1) it is able to measure the local density of states of quasiparticles, N s ðE; rÞ, with atomic spatial resolution and to image the vortex lattice in real space. The quasi-particles in a superconductor are represented by the Bogoliubovde Gennes equation as particles moving in the pair potential ÁðrÞ. Superconductivity is degraded near the vortex core, where the quasi-particles are confined and the bound states are formed. The anisotropy of ÁðrÞ is expected to be determined by imaging the vortex core by STM/STS.We have investigated the vortex core in the borocarbide YNi 2 B 2 C. An anisotropy of a superconducting energy gap has been proposed from measurements of the specific heat, 2-5) thermal conductivity, 6,7) photoemission spectroscopy 8) and ultrasonic attenuation. 9) Our recent LT-STS measurements in zero magnetic field imply a large anisotropy of the gap (Á max % 4.0 meV, Á min 0.5 meV). 10) In an anisotropic superconductor, the anisotropic vortex core reflecting the gap symmetry was predicted by Ichioka et al.11) However, the vortex core observed with STS in YNi 2 B 2 C 12) and the related system LuNi 2 B 2 C 13) at 4.2 K did not exhibit anisotropy. The purpose of this paper is to clarify the detailed structure of the vortex core in YNi 2 B 2 C through measurements of N s ðE; rÞ using LT-STM/STS at lower temperatures. In the present experiment, we have found the fourfold-symmetric vortex core and the bound states in the vortex core in YNi 2 B 2 C by STS for the first time.Single crystals of YNi 2 B 2 C were grown by the floating zone method. The samples for our present STS experiments were obtained from the same batch and the typical shape was 1:0 mm Â 1:0 mm Â 3:0 mm 3 . The critical temperature T c was determined to be 15.6 K from dc magnetization measurement. The residual resistivity ratio RRR was 28.8, and the resistivity at T c was 1.2 m cm, while in our previous experiment, 12) the RRR of the sample was about 6. The mean free path ' of the present sample was calculated to be 70 nm from the RRR using the electronic density of states at the Fermi energy.14) The upper critical field H c2 is about 8 T. From the formula H c2 ¼ 0 =2 2 , the coherence length was calculated to be 6.3 nm. Since ' is ten t...

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Superconductivity in Quaternary Borocarbides

Nagarajan

Mazumdar

Hossain

et al. 2005

Frontiers in Superconducting Materials

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Imaging of a Vortex Lattice Transition inYNi2B2Cby Scanning Tunneling Spectroscopy

Cited by 85 publications

References 16 publications

Tunneling spectroscopy in the magnetic superconductorTmNi2B2C

Tunneling spectroscopy in the magnetic superconductorTmNi2B2C

First Observation of the Fourfold-symmetric and Quantum Regime Vortex Core in YNi₂B₂C by Scanning Tunneling Microscopy and Spectroscopy

Superconductivity in Quaternary Borocarbides

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Imaging of a Vortex Lattice Transition inYNi2B2Cby Scanning Tunneling Spectroscopy

Cited by 85 publications

References 16 publications

Tunneling spectroscopy in the magnetic superconductorTmNi2B2C

Tunneling spectroscopy in the magnetic superconductorTmNi2B2C

First Observation of the Fourfold-symmetric and Quantum Regime Vortex Core in YNi2B2C by Scanning Tunneling Microscopy and Spectroscopy

Superconductivity in Quaternary Borocarbides

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First Observation of the Fourfold-symmetric and Quantum Regime Vortex Core in YNi₂B₂C by Scanning Tunneling Microscopy and Spectroscopy