Theoretical study of I-V characteristics in a coupled long Josephson junctions based on magnesium diboride superconductor

TL;DR

This theoretical study models the I-V characteristics of a magnesium diboride-based coupled long Josephson junction, revealing non-linear behaviors and negative resistance regions relevant for electronic device applications.

Contribution

The paper develops a microscopic Hamiltonian-based theoretical framework for Josephson junctions, incorporating complex inter- and intra-band interactions and solving the resulting equations numerically.

Findings

I-V characteristics are linear at low voltage and non-linear at high voltage.

Negative resistance regions are identified, indicating potential for electronic device use.

Non-linearity depends on junction and layer thicknesses.

Abstract

In the present work, the current-voltage (I-V) characteristics in a coupled long Josephson junction based on magnesium diboride are studied by establishing a system of equations of phase differences of various inter- and intra-band channels starting from the microscopic Hamiltonian of the junction system and simplifying it through the phenomenological procedures such as action, partition function, Hubbard-Stratonovich transformation (bosonization), Grassmann integral, saddle-point approximation, Goldstone mode, phase dependent effective Lagrangian and, finally, Euler-Lagrange equation of motion. The system of equations are solved using finite difference approximation for which the solution of unperturbed sine-Gordon equation is taken as the initial condition. Neumann boundary condition is maintained at both the ends so that the fluxon is capable of reflecting from the end of the system. The phase dependent current is calculated for different tunnel voltage and averaged out over space and time. The current-voltage characteristics are almost linear at low voltage and non-linear at higher voltage which indicates that the more complicated physical phenomena at this situation may occur. At some region of the characteristics, there exist a negative resistance which means that the junction system can be used in specific electronic devices such as oscillators, switches, memories etc. The non-linearity is also sensitive to the layer as well as to the junction thicknesses. Non-linearity occurs for lower voltage and for higher junction and layer thicknesses.