Vortex Pinning in Ion-Irradiated Nb<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Se</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>Studied by Scanning Tunneling Microscopy

Behler, S.; Pan, S. H.; Jess, P.; Baratoff, A.; Güntherodt, H.‐J.; Lévy, F.; Wirth, G.; Wiesner, J.

doi:10.1103/physrevlett.72.1750

Cited by 65 publications

(22 citation statements)

References 14 publications

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“…A distorted hexagonal symmetry and vortex chains were predicted and observed by Bitter decoration [11], neutron scattering [12], and STM [8] in YBCO and BSCCO along with sawtooth VLs, hexatic lattices, order-disorder transitions, intrinsic pinning, and pinning by twin boundaries. Analogous features were found in NbSe 2 by STM [5,7] and Bitter decoration [11].…”

supporting

confidence: 61%

“…STM, in contrast, is sensitive to the local density of states on the much smaller scale of the coherence length j and can image vortices even at high fields, where the vortex spacing is smaller than l. So far, surface quality has limited the observation of vortices by STM to two materials: NbSe 2 , which presents clean atomically flat surfaces [4][5][6][7], and crystals of YBCO grown in special BaZrO 3 crucibles [8].…”

mentioning

confidence: 99%

“…Most other techniques, such as magnetic force microscopy [1], Bitter decoration [2], and neutron scattering [3], are sensitive to magnetic contrast on the scale of the London penetration depth l and are therefore limited to low magnetic fields. STM, in contrast, is sensitive to the local density of states on the much smaller scale of the coherence length j and can image vortices even at high fields, where the vortex spacing is smaller than l. So far, surface quality has limited the observation of vortices by STM to two materials: NbSe 2 , which presents clean atomically flat surfaces [4][5][6][7], and crystals of YBCO grown in special BaZrO 3 crucibles [8].…”

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Scanning Tunneling Microscopy Observation of a Square Abrikosov Lattice inLuNi2B2C

et al. 1997

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We present scanning tunneling microscopy measurements of the (001) surface of a LuNi 2 B 2 C borocarbide single crystal at 4.2 K. In zero field, the conductance versus voltage characteristics recorded at various locations on the sample reproducibly provide a gap value of 2.2 meV. In a magnetic field of 1.5 and 0.375 T, the recordings of the conductance as a function of position reveal a regular square vortex lattice tilted by 45 ± with respect to the crystalline a axis. This unusual result is correlated with an in-plane anisotropy of the upper critical field H k c2 ͑45 ± ͒͞H k c2 ͑0͒ 0.92 at 4.2 K and is analyzed within the framework of Ginzburg-Landau theory.[S0031-9007 (97)03335-8] PACS numbers: 74.60.Ge The scanning tunneling microscope (STM) is a powerful probe of the real space structure of the vortex lattice (VL) of type-II superconductors. Most other techniques, such as magnetic force microscopy [1], Bitter decoration [2], and neutron scattering [3], are sensitive to magnetic contrast on the scale of the London penetration depth l and are therefore limited to low magnetic fields. STM, in contrast, is sensitive to the local density of states on the much smaller scale of the coherence length j and can image vortices even at high fields, where the vortex spacing is smaller than l. So far, surface quality has limited the observation of vortices by STM to two materials: NbSe 2 , which presents clean atomically flat surfaces [4][5][6][7], and crystals of YBCO grown in special BaZrO 3 crucibles [8].Although the VL forms a hexagonal structure for isotropic superconductors in the absence of pinning [9,10], many deviations from this symmetry have been found, generally associated with anisotropic uniaxial character or pinning by extrinsic defects. A distorted hexagonal symmetry and vortex chains were predicted and observed by Bitter decoration [11], neutron scattering [12], and STM [8] in YBCO and BSCCO along with sawtooth VLs, hexatic lattices, order-disorder transitions, intrinsic pinning, and pinning by twin boundaries. Analogous features were found in NbSe 2 by STM [5,7] and Bitter decoration [11].On the low T c materials Nb and Pb-Tl, hexagonal, distorted hexagonal, and square VLs, depending on the crystal orientation, were observed by Bitter decoration [13,14] and neutron scattering experiments [15]. A gradual phase transition in Pb-Tl(111) of the VL from hexagonal to square for increasing field was observed and explained by an attractive interaction between the vortices when the vortex spacing is of the order of the coherence length in this low k material [16,17]. In recent neutron scattering experiments [3] a square VL which transforms to hexago-nal at very low fields [18] was observed in an ErNi 2 B 2 C single crystal. This compound belongs to the recently discovered borocarbide family [19,20] and exhibits an antiferromagnetic ordering which was shown to directly influence the VL [3].To avoid any possible coupling between magnetic ordering and the VL, we performed STM investigations on LuNi 2 B 2 C which has...

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confidence: 61%

mentioning

confidence: 99%

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confidence: 99%

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Scanning Tunneling Microscopy Observation of a Square Abrikosov Lattice inLuNi2B2C

et al. 1997

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“…The first experiments of Hess et al were followed by many other studies ͑Renner et Behler et al, 1994͒. The standard way to detect vortices in NbSe 2 is to map the conductance measured at the energy of the coherence peaks. An example is shown in Fig.…”

Section: Nbse 2 and Other Conventional Superconductorsmentioning

confidence: 99%

Scanning Tunneling Spectroscopy on High Temperature Superconductors

Fischer

Renner

Maggio-Aprile

NATO Science Series: B:

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Tunneling spectroscopy has played a central role in the experimental verification of the microscopic theory of superconductivity in classical superconductors. Initial attempts to apply the same approach to high-temperature superconductors were hampered by various problems related to the complexity of these materials. The use of scanning tunneling microscopy and spectroscopy ͑STM and STS͒ on these compounds allowed the main difficulties to be overcome. This success motivated a rapidly growing scientific community to apply this technique to high-temperature superconductors. This paper reviews the experimental highlights obtained over the last decade. The crucial efforts to gain control over the technique and to obtain reproducible results are first recalled. Then a discussion on how the STM and STS techniques have contributed to the study of some of the most unusual and remarkable properties of high-temperature superconductors is presented: the unusually large gap values and the absence of scaling with the critical temperature, the pseudogap and its relation to superconductivity, the unprecedented small size of the vortex cores and its influence on vortex matter, the unexpected electronic properties of the vortex cores, and the combination of atomic resolution and spectroscopy leading to the observation of periodic local density of states modulations in the superconducting and pseudogap states and in the vortex cores.

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“…2 The complete mapping of the tunneling conductance in real space as a function of applied bias provided a large data set, in striking agreement with the BCS predictions for the local density of states (LDOS) of a vortex. 3 Since then, several groups have investigated the vortex cores by STM in NbSe 2 , [4][5][6] in other classical superconductors, [7][8][9][10][11] in high-T c cuprates, 12 and, more recently, in the pnictides. [13][14][15][16] While in classical superconductors, including the pnictides, these studies usually reveal vortex-core spectra in good qualitative agreement with the BCS theory, significant deviations are found in high-T c superconductors, probably due to an anomalous normal state.…”

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Quasiparticle spectra of Abrikosov vortices in a uniform supercurrent flow

Berthod

2013

Phys. Rev. B

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We calculate the local density of states of a vortex in a two-dimensional s-wave superconductor in the presence of a uniform applied supercurrent. The supercurrent induces changes in the electronic structure for the isolated vortex as well as the vortex lattice, which agree with the recent measurements in 2H -NbSe 2 [Maldonado et al., Phys. Rev. B 88, 064518 (2013)]. We find that the supercurrent polarizes the core states when the vortices are pinned. This shows that the transfer of momentum from the supercurrent to the bound states and the rigidity of the wave functions must be considered for understanding the various forces acting on collectively pinned Abrikosov vortices. The quantum states bound to magnetic vortices in type-II superconductors carry information about the fundamental properties of the superconducting state. The existence of bound states was predicted long ago, 1 but the direct observation in NbSe 2 awaited the invention of the scanning tunneling microscope (STM). 2 The complete mapping of the tunneling conductance in real space as a function of applied bias provided a large data set, in striking agreement with the BCS predictions for the local density of states (LDOS) of a vortex. 3 Since then, several groups have investigated the vortex cores by STM in NbSe 2 , 4-6 in other classical superconductors, 7-11 in high-T c cuprates, 12 and, more recently, in the pnictides. [13][14][15][16] While in classical superconductors, including the pnictides, these studies usually reveal vortex-core spectra in good qualitative agreement with the BCS theory, significant deviations are found in high-T c superconductors, probably due to an anomalous normal state. 12 The interpretation of vortex-core spectra in the cuprates remains an open question.Recently, a measurement of the vortex electronic structure in the presence of an in-plane current flow was performed in NbSe 2 . 17 When a supercurrent is established across a vortex lattice, a "Lorentz force" acts on the vortices in the direction normal to the applied current. 18 In Ref. 17, the current was sufficiently small for the force to remain below the depinning threshold, and the authors could map the LDOS of static vortices with and without the applied current. The main observation of this experiment is that the application of a current transfers low-energy spectral weight from inside the cores, where the zero-bias conductance is reduced, to in between the vortices where it is enhanced, while the converse appears at the gap edges, where the spectral weight is enhanced inside the cores and depleted outside. The measurements also suggest that the current increases the size of the vortex cores. To interpret these trends, the authors assume that the applied current reduces the smallest gap on the two-band Fermi surface of NbSe 2 . This would affect the formation of Andreev bound states in the cores, diminishing their energy separation.This interpretation refers to second-order changes in the modulus of the order parameter but ignores that the leading effect of ...

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Vortex Pinning in Ion-Irradiated NbSe2Studied by Scanning Tunneling Microscopy

Cited by 65 publications

References 14 publications

Scanning Tunneling Microscopy Observation of a Square Abrikosov Lattice inLuNi2B2C

Scanning Tunneling Microscopy Observation of a Square Abrikosov Lattice inLuNi2B2C

Scanning Tunneling Spectroscopy on High Temperature Superconductors

Quasiparticle spectra of Abrikosov vortices in a uniform supercurrent flow

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