Nanoscale superconducting properties of amorphous W-based deposits grown with a focused-ion-beam

Guillamón, Isabel; Suderow, Hermann; Vieira, S.; Fernández-Pacheco, Amalio; Sesé, J.; Córdoba, R.; Teresa, J. M. De; Ibarra, M. R.

doi:10.1088/1367-2630/10/9/093005

Cited by 70 publications

(95 citation statements)

References 39 publications

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“…50 For instance, the peak observed at the vortex core in 2H -NbSe 2 is about 1/3 of the gap value. 26,27 The zero-bias conductance peak we observe here has a strong broadening, of the same order as the gap value. Broadening of zero-bias conductance peaks in superconductors has been related to impurities, random disorder, or complex gap variations over the Fermi surface.…”

Section: Discussionmentioning

confidence: 57%

“…48 The first such state is located very close to zero energy (at 2 /E F , which is generally small) and has been seen in the STM experiments as a zero-bias peak. 26,27 At zero magnetic field, in-gap bound states also arise at magnetic impurities in s-wave superconductors. [49][50][51] Their energy location depends on the relative amplitude of electron and hole impurity wave functions, which is governed by the exchange interaction between the localized magnetic moments of the impurity and the Cooper pairs, or by the scattering phase shift.…”

Section: Discussionmentioning

confidence: 99%

“…Note that the superconducting gap observed in multilayers is strongly smeared, with a high number of states at zero bias, contrasting well developed gap structures found in the other 2H transition-metal dichalcogenides. 10,12,26,27 Magnetic fields of 10 mT, applied perpendicular to the sample, lead to flat tunneling conductance curves both in single layers and in multilayers. Such fields are at the lower limit of our coil and magnet power supply system, and thus we did not follow the temperature dependence of the upper critical field nor study spatial gap dependences under field.…”

Section: Tmentioning

confidence: 99%

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Scanning tunneling measurements of layers of superconducting 2H-TaSe2: Evidence for a zero-bias anomaly in single layers

et al. 2013

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We report a characterization of surfaces of the dichalcogenide TaSe 2 using scanning tunneling microscopy and spectroscopy at 150 mK. When the top layer has the 2H structure and the layer immediately below the 1T structure, we find a singular spatial dependence of the tunneling conductance below 1 K, changing from a zero-bias peak on top of Se atoms to a gap in between Se atoms. The zero-bias peak is additionally modulated by the commensurate 3a 0 × 3a 0 charge-density wave of 2H -TaSe 2 . Multilayers of 2H -TaSe 2 show a spatially homogeneous superconducting gap with a critical temperature also of 1 K. We discuss possible origins for the peculiar tunneling conductance in single layers.

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Section: Discussionmentioning

confidence: 57%

Section: Discussionmentioning

confidence: 99%

Section: Tmentioning

confidence: 99%

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Scanning tunneling measurements of layers of superconducting 2H-TaSe2: Evidence for a zero-bias anomaly in single layers

et al. 2013

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“…The dependence of the superconducting properties of these wires on the deposition conditions has been investigated in detail in Li et al 7 The superconducting gap as well as the Abrikosov flux lattice have been studied by scanning tunneling microscopy experiments. 8 The investigation of proximity- induced superconductivity in metallic nanowires contacted by FIB has also been recently performed. 9 The advantages of this technique are the deposition of the material of practically any shape and size, without any mask, and the good quality of the interface created.…”

Section: The Samplesmentioning

confidence: 99%

Geometry-related magnetic interference patterns in longSNSJosephson junctions

et al. 2012

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We have measured the critical current dependence on the magnetic flux of two long SNS junctions differing by the normal wire geometry. The samples are made by a Au wire connected to W contacts, via focused ion beam assisted deposition. We could tune the magnetic pattern from the monotonic Gaussian-like decay of a quasi-one-dimensional (1D) normal wire to the Fraunhofer-like pattern of a square normal wire. We explain the monotonic limit with a semiclassical 1D model, and we fit both field dependencies with numerical simulations of the two-dimensional Usadel equations. Furthermore, we observe both integer and fractional Shapiro steps. The magnetic flux dependence of the integer steps reproduces as expected that of the critical current I c , while fractional steps decay slower with the flux than I c .

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“…R W −e vanishes below the critical parameters (critical temperature T C , critical current I C , and upper critical field B C2 ) of the W-based superconducting nanodeposit, which is an extreme type-II superconductor following closely simple s-wave BCS theory. 11 The FIBID-Pt nanodeposits are grown first and the FIBID-W electrode afterwards. The FEBID-Co electrode is grown in the last step and is never irradiated by the Ga ions, which warrants its high-quality magnetic and transport properties.…”

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confidence: 99%

Andreev reflection under high magnetic fields in ferromagnet-superconductor nanocontacts

et al. 2011

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We study the magnetic-field dependence of the conductance in planar ferromagnet-superconductor nanocontacts created with focused-electron/ion-beam techniques. From the fits of the differential conductance curves in high magnetic fields, we obtain the magnetic field dependences of the superconducting gap and the broadening parameter. Orbital depairing is found to be linear with magnetic field. We evaluate the magnetic field dependence of the quasiparticle density of states, and we compare it with the value obtained by scanning tunneling spectroscopy experiments. The study of the differential conductance (that is the first derivative of the I-V characteristic, dI/dV) of point contacts has been demonstrated to be an effective tool to probe the interaction mechanisms in conductive materials: inelastic scattering of electrons by phonons, 1 scattering of electrons by magnons, 2 etc. If one of the electrodes forming the point contact is superconductor, through the study of the Andreev reflection 3 (AR) occurring at the interface it is possible to obtain information on the superconducting gap. In ferromagnet-superconductor point contacts, along with the information on the superconductor gap, the ferromagnet spin polarization can be extracted, 4,5 making this type of study very appealing.The superconductor density of states under magnetic field is a relevant parameter in basic studies of superconductivity as well as in applications where the superconductor is under the influence of high magnetic fields. AR measurements in a magnetic field provide further information on the properties of the superconducting 6 and ferromagnetic electrodes of the contact. So far no systematic investigations of ferromagnetsuperconductor nanocontacts under high magnetic fields have been carried out. A comprehensive study of the effect of a magnetic field on the transport properties of ferromagnetsuperconductor nanocontacts is due to 7 and the maximum magnetic field applied in this study is 16.5 mT, since the critical field of the Al electrode used as the superconducting electrode is 15 mT. In this Brief Report, we propose a different approach to evaluate the magneticfield dependence of the quasiparticle density of states of superconductors from the measurement of the conductance in high magnetic fields.The nanocontacts are created between a superconducting W nanodeposit and a magnetic Co nanodeposit under high vacuum conditions using commercial dual beam equipment that integrates a focused electron column and a focused Ga ion column forming 52 degrees. Focused-electron-beam-induced deposition of magnetic Co (FEBID-Co) and focused-ionbeam-induced deposition of superconducting W (FIBID-W) are made following previous work. [8][9][10] Nanocontacts are obtained by suitably nanoshaping the Co-based magnetic deposit into a sharp tip-like structure, contacting the W-based superconductor. Importantly, the two electrodes forming the contact are grown under high vacuum, minimizing oxidation during contact formation. The in situ monitoring of the resista...

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Nanoscale superconducting properties of amorphous W-based deposits grown with a focused-ion-beam

Cited by 70 publications

References 39 publications

Scanning tunneling measurements of layers of superconducting 2H-TaSe2: Evidence for a zero-bias anomaly in single layers

Scanning tunneling measurements of layers of superconducting 2H-TaSe2: Evidence for a zero-bias anomaly in single layers

Geometry-related magnetic interference patterns in longSNSJosephson junctions

Andreev reflection under high magnetic fields in ferromagnet-superconductor nanocontacts

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