Current-voltage characteristics of tunnel Josephson junctions with a ferromagnetic interlayer

Abstract

We present a quantitative study of the current-voltage characteristics (CVC) of diffusive superconductor/ insulator/ferromagnet/superconductor (SIFS) tunnel Josephson junctions. In order to obtain the CVC we calculate the density of states (DOS) in the F/S bilayer for arbitrary length of the ferromagnetic layer, using quasiclassical theory. For a ferromagnetic layer thickness larger than the characteristic penetration depth of the superconducting condensate into the F layer, we find an analytical expression which agrees with the DOS obtained from a self-consistent numerical method. We discuss general properties of the DOS and its dependence on the parameters of the ferromagnetic layer. In particular we focus our analysis on the DOS oscillations at the Fermi energy. Using the numerically obtained DOS we calculate the corresponding CVC and discuss their properties. Finally, we use CVC to calculate the macroscopic quantum tunneling (MQT) escape rate for the current biased SIFS junctions by taking into account the dissipative correction due to the quasiparticle tunneling. We show that the influence of the quasiparticle dissipation on the macroscopic quantum dynamics of SIFS junctions is small, which is an advantage of SIFS junctions for superconducting qubits applications.

Mesoscopic electron transport and atomic gases, a review of Frank W. J. Hekking's scientific work

“…Features of the density of states manifest on the current-voltage characteristics that have been also calculated in Ref. [26].…”

“…In a later work of Frank Hekking with collaborators, an exhaustive description of the current voltage characteristics of diffusive SFS junctions was provided [26]. Because of the presence of an exchange field, the sign of change on the density of states of the magnetic F layer at the Fermi level depends on the thickness of the F layer.…”

The effect of normal and insulating layers on 0-πtransitions in Josephson junctions with a ferromagnetic barrier

“…The critical current density is given by the expression (12). For FJJs without an N layer, the critical current density has already been calculated in [28,45,52,53].…”

“…Second, an N layer between F and S is often technologically necessary to produce high-quality JJs [24,26,27,[30][31][32][33][35][36][37][38], for example by preventing diffusion between F and S films [39]. The presence of an N layer in FJJs was not taken into account in any theoretical work [44,[40][41][42][43]45] (see also [2,3] for review) in spite of numerous experiments. We show that this is reasonable only if the F and N metals behave fully identically, except for their magnetic properties.…”

Electrodynamics of Highly Spin-Polarized Tunnel Josephson Junctions

“…This has hampered the use of ferromagnetic JJs as active switching elements in different classical and quantum circuits, since for such applications it is important to have a rather high I c R N product and low damping [13]. Low-dissipative ferromagnetic junctions use an additional insulating layer between one of the superconducting electrodes and the ferromagnetic barrier (SIFS JJs) [7,[15][16][17] or a ferromagnetic insulator barrier (SI f S JJs) [18][19][20][21][22] and may present key advantages for some applications, thus increasing the overall impact of JJs based on ferromagnetic barriers [7,16,17,23,24].…”