Scaling behavior of point contacts between a tungsten tip and the heavy-fermion superconductors

Gloos, K.; Anders, Frithjof B.; Buschinger, B.; Geibel, C.; Heuser, Kjell; Jährling, F.; Kim, J. S.; Klemens, R.; Müller-Reisener, R.; Schank, C.; Stewart, G. R.

doi:10.1007/bf00754627

Cited by 36 publications

(37 citation statements)

References 35 publications

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“…This extreme cleanness of CeCoIn 5 together with Pauli-limited upper critical field enables the long-standing Fulde-Ferrell-Larkin-Ovchinikov phase transition to be observed for the first time [24] in this material. Consequently, the arguments proposed by Gloos et al [25], attributing the suppressed ESGC to the non-ballistic nature of the contact, are not valid for our measurements.…”

contrasting

confidence: 78%

“…In our case, proximity [31] and pressure effects [28,32] are ruled out, since the ESGC is observed to accompany the superconducting transition. Moreover, the ballistic nature of the contact excludes the local heating effect [6,28] and the dominant Maxwell resistance [25]. Therefore, we claim that there must be intrinsic origins causing AR conductance in N/HFS contacts to be reduced severely.…”

mentioning

confidence: 86%

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Andreev reflection at the normal-metal/heavy-fermion superconductorCeCoIn5interface

et al. 2005

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The dynamic conductance of the heavy-fermion superconductor CeCoIn 5 is measured by pointcontact spectroscopy as a function of temperature from 60 K down to 400 mK. The contact between the gold tip and the single-crystal is shown to be in the Sharvin limit with the enhanced sub-gap conductance arising from Andreev reflection. The zero-bias conductance data are best fit using the extended Blonder-Tinkham-Klapwijk model with a d-wave superconducting order parameter. A fit to the full conductance curve at 400 mK indicates strong coupling (2∆(0)/k B T c = 4.6) and quantifies the suppressed Andreev reflection signal, which is a signature of normal-metal/heavy-fermion superconductor junctions. Possibilites for theoretical modeling to account for the suppressed Andreev conductance are suggested.

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confidence: 78%

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confidence: 86%

Andreev reflection at the normal-metal/heavy-fermion superconductorCeCoIn5interface

et al. 2005

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“…it increases with the rate about 3×10 4 A/cm 2 per 1 mV 1 . Thus, as Gloos et al concluded [20], the resistive Maxwell term contributes mainly to the observed SC sharp minimum. Recovering the Maxwell resistance, which is zero in the SC state, due to increasing of the current density and/or temperature in the PC core in consequence of Joule heating produces a zero-bias minimum.…”

Section: Discussionmentioning

confidence: 57%

Analysis of nonlinear conductivity of point contacts on the base of FeSe in the normal and superconducting state

Naǐdyuk

Gamayunova

Kvitnitskaya

et al. 2016

Low Temperature Physics

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Nonlinear conductivity of point contacts (PCs) on the base of FeSe single crystals has been investigated. Measured dV/dI dependencies demonstrate the prevailing contribution to the PC conductivity caused by the degraded surface. Superconducting (SC) feature in dV/dI like a sharp zero-bias minimum develops for relatively low ohmic PCs, where the deep areas of FeSe are involved. Analysis of dV/dI has shown that the origin of the zero-bias minimum is connected with the Maxwell part of the PC resistance, what masks energy dependent spectral peculiarities. Even so, we have found the specific features in dV/dI -the sharp side maxima, which may have connection to the SC gap, since their position follows the BCS temperature dependence. Exploring the dV/dI spectra of the rare occurrence with Andreev-like structure, the two gaps with Δ=2.5 and 3.5 meV were identified.

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“…16 In fact, for this reason tungsten tip has been used for PCS of heavy fermion superconductors. 17 A consequence of using a hard tip is that the tip will exert some pressure on the surface which may affect the SC, 18 possibly due to local distortion of lattice. 19,20 It is known that for SRO a very low uniaxial pressure of 0.2 GPa along the c axis can enhance the superconducting transition temperature (T c ) of pure SRO from 1.5 K up to 3.2 K, 21,22 and recently in-plane strain (0.23%) along 100 direction is also shown to enhance T c from 1.3 K up to 1.9 K. 23 The pressure in abovementioned measurements were applied to bulk samples, while for PCS the pressure is exerted locally.…”

Section: 5mentioning

confidence: 99%

“…It is still not clear whether the order parameter symmetry can be verified strictly from the shape of the point contact Andreev reflection spectra. 17,48 In this work we mainly report the temperature and field dependence of the PC spectra rather than quantitatively fit the data with the generalized BTK model.…”

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confidence: 99%

Enhanced superconductivity at the interface ofW/Sr2RuO4point contacts

et al. 2015

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Differential resistance measurements are conducted for point contacts (PCs) between tungsten tip approaching along the c axis direction and the ab plane of Sr2RuO4 single crystal. Three key features are found. Firstly, within 0.2 mV there is a dome like conductance enhancement due to Andreev reflection at the normal-superconducting interface. By pushing the W tip further, the conductance enhancement increases from 3% to more than 20%, much larger than that was previously reported, probably due to the pressure exerted by the tip. Secondly, there are also superconducting like features at bias higher than 0.2 mV which persists up to 6.2 K, resembling the enhanced superconductivity under uniaxial pressure for bulk Sr2RuO4 crystals but more pronounced here. Third, the logarithmic background can be fitted with the Altshuler-Aronov theory of tunneling into quasi two dimensional electron system, consistent with the highly anisotropic electronic system in Sr2RuO4.The layered perovskite ruthenate Sr 2 RuO 4 (SRO) has shown evidence for spin-triplet, odd-parity superconductivity (SC) which may be useful for topological quantum computation.

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Scaling behavior of point contacts between a tungsten tip and the heavy-fermion superconductors

Cited by 36 publications

References 35 publications

Andreev reflection at the normal-metal/heavy-fermion superconductorCeCoIn5interface

Andreev reflection at the normal-metal/heavy-fermion superconductorCeCoIn5interface

Analysis of nonlinear conductivity of point contacts on the base of FeSe in the normal and superconducting state

Enhanced superconductivity at the interface ofW/Sr2RuO4point contacts

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