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

Naǐdyuk, Yu. G.; Gamayunova, N. V.; Kvitnitskaya, O. E.; Fuchs, G.; Чареев, Д. А.; Vasiliev, A. N.

doi:10.1063/1.4939153

Cited by 6 publications

(15 citation statements)

References 28 publications

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“…The dV/dI curves in Fig. 1a are asymmetric with an enhanced value at negative bias similar to our previous data in [14], so that the calculated antisym- Fig. 1b).…”

Section: Resultssupporting

confidence: 86%

“…Additionally, we reported such correlation also for FeSe in Ref. [14]. Our soft PC's mainly had a negative value of dV/dI as and only about one third of all PC's exhibited a positive dV/dI as prior the dV/dI as sign changes (see Fig.1b).…”

Section: Discussionsupporting

confidence: 72%

“…We note the perfect reproducibility of the SC features in dV/dI, i. e. almost all of the more than twenty soft PC's with resistance in the range 0.4 -5Ω show the pronounced double-minimum structure in dV/dI. It is in contrast to our previous measurements on the same FeSe crystals using a needle-anvil geometry with tips from Cu, Ag or W thin wires [14,15], where the double-minimum structure in dV/dI appeared very rarely. At the same time, soft PC's with the higher resistance display dV/dI with weak zero bias minimum or absence of any SC features at all, similar to the needle-anvil type PC's shown on Fig.…”

Section: Methodscontrasting

confidence: 76%

“…At the same time, soft PC's with the higher resistance display dV/dI with weak zero bias minimum or absence of any SC features at all, similar to the needle-anvil type PC's shown on Fig. 1 in [14].…”

Section: Methodssupporting

confidence: 59%

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Superconducting gaps in FeSe studied by soft point-contact Andreev reflection spectroscopy

et al. 2017

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FeSe single crystals have been studied by soft point-contact Andreev-reflection spectroscopy. Superconducting gap features in the differential resistance dV /dI(V ) of point contacts such as a characteristic Andreev-reflection double-minimum structure have been measured versus temperature and magnetic field. Analyzing dV /dI within the extended two-gap Blonder-Tinkham-Klapwijk model allows to extract both the temperature and magnetic field dependence of the superconducting gaps. The temperature dependence of both gaps is close to the standard BCS behavior. Remarkably, the magnitude of the double-minimum structure gradually vanishes in magnetic field, while the minima position only slightly shifts with field indicating a weak decrease of the superconducting gaps. Analyzing the dV /dI(V ) spectra for 25 point contacts results in the averaged gap values ∆L = 1.8±0.4 meV and ∆S =1.0±0.2 meV and reduced values 2 ∆L /kBTc=4.2± 0.9 and 2 ∆S /kBTc=2.3±0.5 for the large (L) and small (S) gap, respectively. Additionally, the small gap contribution was found to be within tens of percent decreasing with both temperature and magnetic field. No signatures in the dV /dI spectra were observed testifying a gapless superconductivity or presence of even smaller gaps.

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“…The dV/dI curves in Fig. 1a are asymmetric with an enhanced value at negative bias similar to our previous data in [14], so that the calculated antisym- Fig. 1b).…”

Section: Resultssupporting

confidence: 86%

Section: Discussionsupporting

confidence: 72%

Section: Methodscontrasting

confidence: 76%

Section: Methodssupporting

confidence: 59%

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Superconducting gaps in FeSe studied by soft point-contact Andreev reflection spectroscopy

et al. 2017

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“…The analytical expression for the conductivity of the microcontact obtained from the solution of the Bogolyubov-de Gennes equations made it possible to establish an important difference between s þþ and s 6 -wave symmetry in a two-band superconductor, which can be used to interpret the corresponding experiments of microcontact spectroscopy of "iron" superconductors. [72][73][74][75][76]…”

Section: An Anomalous Proximity Effect At the Boundary Of S And S 6wamentioning

confidence: 99%

Proximity and Josephson effects in microstructures based on multiband superconductors (Review Article)

Yerin

Omelyanchouk

2017

Low Temperature Physics

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Emerging in the 1950s, the multiband superconductivity has been considered for a long time as an approximate model in the form of a generalization of the BCS theory to the case of two bands for a more accurate quantitative description of the properties and characteristics of such superconductors as cuprates, heavy fermions compounds, metal boron carbides, fullerides, strontium ruthenate etc. due to their complex piecewise-continuous Fermi surfaces. However the discovery of the multiband structure of the superconducting state in magnesium diboride in 2001 and iron oxypnictides and chalcogenides in 2008 led to the appearance of many papers in which effects and different dependences well known for conventional single-band s-wave superconductors were reexamined. The main purpose of these studies was to reveal the symmetry type of the order parameter, which provides an important information about the mechanism of Cooper pairing in these superconductors. One of the most effective methods of obtaining information on the symmetry properties of the order parameter in the multiband superconductors is phase-sensitive techniques. This review summarizes the results of theoretical and experimental studies of the proximity and Josephson effects in systems based on multiband superconductors in contact with normal metals, insulators and other superconductors.

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Metamorphoses of electronic structure of FeSe-based superconductors (Review Article)

Pustovit

Kordyuk

2016

Low Temperature Physics

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The electronic structure of FeSe, the simplest iron based superconductor (Fe-SC), conceals a potential of dramatic increase of Tc that realizes under pressure or in a single layer film. This is also the system where nematicity, the phenomenon of a keen current interest, is most easy to study since it is not accompanied by the antiferomagnetic transition like in all other Fe-SC's. Here we overview recent experimental data on electronic structure of FeSe-based superconductors: isovalently doped crystals, intercalates, and single layer films, trying to clarify its topology and possible relation of this topology to superconductivity. We argue that the marked differences between the experimental and calculated band structures for all FeSe compounds can be described by a hoping selective renormalization model for a spin/orbital correlated state that may naturally explain both the evolution of the band structure with temperature and nematicity.

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

Cited by 6 publications

References 28 publications

Superconducting gaps in FeSe studied by soft point-contact Andreev reflection spectroscopy

Superconducting gaps in FeSe studied by soft point-contact Andreev reflection spectroscopy

Proximity and Josephson effects in microstructures based on multiband superconductors (Review Article)

Metamorphoses of electronic structure of FeSe-based superconductors (Review Article)

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