Superconductivity

Josephson effect in FeSe point contacts

M. V. Golubkov^a, V. A. Stepanov^a, A. V. Sadakov^a, A. S. Usol'tsev^a, D. A. Chareev<sup>bcd

a</sup> P. N. Lebedev Physical Institute, Russian Academy of Sciences, Moscow
^b Institute of Experimental Mineralogy, Russian Academy of Sciences, Chernogolovka
^c Dubna State University, Dubna, Moscow Reg.
^d Institute of Physics and Technology of the Ural Federal University

Abstract: The paper presents the results of studies of PbIn/FeSe and FeSe/FeSe Josephson point contacts tuned in helium with critical currents $I_C$(4.2 K) = 1.80–0.43 mA and characteristic voltages $V_C$(4.2 K) = 0.057–0.144 mV. The dependences of $V_C$ of contacts on temperature $T$ and the dependences of the amplitudes of the current steps on the current-voltage characteristics on the power of electromagnetic radiation PMW with a frequency of 8 GHz were measured. The $V_C(T)$ dependences were well approximated by the known models of SS'S, SIS contacts. The dependences of the amplitudes of the first steps of the contact current on $P_{MW}$ were described by a resistive model with a current proportional to $\sin(\varphi)$ with a normalized frequency of microwave radiation found from the oscillation period of the current steps. The obtained results unambiguously indicated the usual $s$ – symmetry of the order parameters in the FeSe bands.

Keywords: iron-based superconductors, order parameter, Josephson effect, resistive model.

Received: 16.05.2025
Revised: 27.05.2025
Accepted: 27.05.2025

DOI: 10.61011/FTT.2025.05.60739.124-25

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