arXiv subjects

T. E. Shanygina

Publications and source records attributed to T. E. Shanygina.

5 recordsLinked to original sources

arXiv2012

Multigap Superconductivity in GdFeAsO$_{0.88}$ Evidenced by SnS-Andreev Spectroscopy

Using intrinsic multiple Andreev reflection effect (IMARE) spectroscopy we studied superconducting properties of nearly optimal oxygen-deficient GdFeAsO$_{0.88}$ polycrystalline samples (bulk critical temperatures $T_C^{bulk} = 49 ÷52$\,K). Temperature dependences for two superconducting gaps $Δ_{L,S}(T)$ ($T_C^{local} = 48 ÷50$\,K) have been measured in the range from 4.2 to 50\,K. The $Δ_{L,S}(T)$ dependences were found to deviate from the BCS-like function; this suggests an importance of the $k$-space (internal) proximity effect between the two condensates.

cond-mat.supr-con↗

arXiv2012

Investigation of LiFeAs by means of "Break-junction" Technique

In our tunneling investigation using Andreev superconductor - normal metal - superconductor contacts on LiFeAs single crystals we observed two reproducible independent subharmonic gap structures at dynamic conductance characteristics. From these results, we can derive the energy of the large superconducting gap $Δ_L=(2.5 ÷3.4)$ meV and the small gap $Δ_L=(0.9 ÷1)$ meV at $T = 4.2$ K for the $T_C^{local} \approx (10.5 ÷14)$ K (the contact area critical temperature which deviation causes the variation of $Δ_L$). The BCS-ratio is found to be $2Δ_L/k_BT_C = (4.6 ÷5.6)$, whereas $2Δ_S/k_BT_C \ll 3.52$ results from induced superconductivity in the bands with the small gap.

cond-mat.supr-con↗

arXiv2012

Study of the Two-Gap Superconductivity in GdO(F)FeAs by ScS-Andreev Spectroscopy

Current-voltage characteristics and dynamic conductance of the superconductor - constriction - superconductor junctions in GdO(F)FeAs polycrystalline samples with critical temperatures Tc^local = 46 - 53 K were investigated. Two superconducting gaps, the large Delta_L = 10.5 +- 2 meV, and the small one Delta_S = 2.3 +- 0.4 meV were clearly observed at T = 4.2 K. The 2Delta_L/kTc^local = 5.5 +- 1 ratio gives support to the strong coupling mechanism which is responsible for the high Tc value. Temperature dependence of the large gap Delta_L(T) indicates the presence of intrinsic proximity effect (in k-space) between two superconducting condensates.

cond-mat.supr-con↗

arXiv2011

Temperature Dependence of Superconducting Gaps in Mg(Al)B2 System Investigated by SnS-Andreev Spectroscopy

Detailed temperature dependence of both superconducting gaps was obtained directly by means of SnS-Andreev spectroscopy. The Δσ,π(T) -curves were shown to be deviated from standard BCS-like behavior, due to k-space proximity effect between σ- and π- condensates, which could give a key to experimental determination of interband electron-phonon coupling constants. For the first time, an excellent qualitative agreement with theoretical predictions of Nicol and Carbotte, and Moskalenko and Suhl was shown. dI(V)/dV-spectra of SnS-Andreev contacts based on MgB2 samples (with defects of crystal structure), and Mg(Al)B2 polycrystalline samples (with the local critical temperatures Tc variation 10 K < Tc < 37 K) were studied by means of the "break-junction" technique within the temperature range 4.2 K < T < Tc.

cond-mat.supr-con↗

arXiv2011

Observation of Multi-Gap Superconductivity in GdO(F)FeAs by Andreev Spectroscopy

We have studied current-voltage characteristics of Andreev contacts in polycrystalline GdO$_{0.88}$F$_{0.12}$FeAs samples with bulk critical temperature ${T_c}$ = (52.5 \pm 1)K using break-junction technique. The data obtained cannot be described within the single-gap approach and suggests the existence of a multi-gap superconductivity in this compound. The large and small superconducting gap values estimated at T = 4.2K are ΔL = 10.5 \pm 2 meV and ΔS = 2.3 \pm 0.4 meV, respectively.

cond-mat.supr-con↗