Some Properties of Fe1 +ySexTe1 –x Single Crystals in the Superconducting and Normal States

Vedeneev, S. I.; Golubkov, M. V.; Gorina, Yu. I.; Rodin, Vladislav G.; Sadakov, Andrei V.; Sentyurina, N. N.; Sobolevskii, O. A.; Степанов, В. А.; Chernook, S. G.

doi:10.1134/s1063776118090200

Cited by 4 publications

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“…For our type of junctions, , where and are the energy gaps of the two electrodes. Here, none of these methods is viable due to the high critical magnetic field of Ba K (FeAs) , which exceeds 41 in the first case, and because at μV, the curves start changing because of heating, in the second. Thus, as it has also been done in the works published previously 15 , 16 – 25 , as a first approximation, the and of the studied point contacts were determined only from the initial part of the current–voltage characteristic.…”

Section: Discussionmentioning

confidence: 99%

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Probing the current-phase relation in Josephson point-contact junctions between $$\hbox {Pb}_{0.6}$$In$$_{0.4}$$ and $$\hbox {Ba}_{0.6}$$K$$_{0.4}$$(FeAs)$$_2$$ superconductors

Степанов

Lin

Gonnelli

et al. 2021

Sci Rep

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The Josephson effect in point contacts between an “ordinary” superconductor $$\hbox {Pb}_{0.6}$$ Pb 0.6 In$$_{0.4}$$ 0.4 ($$T_c \approx 6.6 \, {\mathrm {K}}$$ T c ≈ 6.6 K ) and single crystals of the Fe-based superconductor Ba$$_{0.6}$$ 0.6 K$$_{0.4}$$ 0.4 (FeAs)$$_2$$ 2 ($$T_c \approx 38.5 \, {\mathrm {K}}$$ T c ≈ 38.5 K ), was investigated. In order to shed light on the order parameter symmetry of Ba$$_{0.6}$$ 0.6 K$$_{0.4}$$ 0.4 (FeAs)$$_2$$ 2 , the dependence of the Josephson supercurrent $$I_s$$ I s on the temperature and on $$\sin (d\varphi )$$ sin ( d φ ) with $$d = 1, 2$$ d = 1 , 2 was studied. The dependencies of the critical current on temperature $$I_c (T)$$ I c ( T ) and of the amplitudes of the first current steps of the current–voltage characteristic $$i_n^{exp} (\sqrt{P})$$ i n exp ( P ) $$(n = 0, 1, 2)$$ ( n = 0 , 1 , 2 ) on the power of microwave radiation with frequency $$f = (1.5 \div 8)\, {\mathrm {GHz}}$$ f = ( 1.5 ÷ 8 ) GHz were measured. It is shown that the dependencies $$I_c (T)$$ I c ( T ) are close to the well-known Ambegaokar–Baratoff (AB) dependence for tunnel contacts between “ordinary” superconductors and to the dependence calculated by Burmistrova et al. (Phys Rev B 91, 214501 (2015)) for microshorts between an “ordinary” superconductor and a two-band superconductor with $$s \pm$$ s ± order parameter symmetry at certain values of the transparency of boundaries and thickness of the transition layer. It is found that the dependencies $$i_n^{exp} (\sqrt{P})$$ i n exp ( P ) cannot be approximated within the resistively shunted model using the normalized microwave frequencies $$\Omega = 2 \pi f / (2eV_c / \hbar )$$ Ω = 2 π f / ( 2 e V c / ħ ) with characteristic voltages $$V_c = I_c R_N$$ V c = I c R N , $$(R_N$$ ( R N —normal resistance of the contact) found from the low-voltage parts of the current–voltage characteristics. The reasons for this failure are discussed and a method is proposed for accurately determining the value of $$\Omega$$ Ω , which takes into account all the features of the point contact affecting the period of the dependence $$i_n^{exp} (\sqrt{P})$$ i n exp ( P ) . An analysis of the $$I_c (T)$$ I c ( T ) and $$i_n^{exp} (\sqrt{P})$$ i n exp ( P ) dependencies shows that the superconducting current of the Josephson contacts under investigation is proportional to the $$\sin$$ sin of the phase difference $$\varphi$$ φ , $$I_s = I_c sin(\varphi )$$ I s = I c s i n ( φ ) . The implications of these results on the symmetry of the order parameter are also discussed.

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Section: Discussionmentioning

confidence: 99%

“…1 b). The PbIn-electrode of the PC in the form of a knife mm long or a pyramid was cut by a razor from a rectangular plate of Pb In 41 . A “fresh” cut of the working surface of PbIn-electrode was always used to create the PC.…”

Section: Methodsmentioning

confidence: 99%