The effect of abnormal superconductor friction

Abstract

The effect of abnormal superconductor friction (ASF) is described in this paper. The experiments conducted proved that, as a result of friction contact in the liquid helium between two test specimens made of metals of group 5 of the periodic table (vanadium, niobium or tantalum), the coefficient of friction, defined as the ratio of the tangential force providing relative sliding of the test specimens to the normal compressive force, is reduced by an order of magnitude and retains its abnormally low value during heating to room temperature. The ASF effect in the case of similar and dissimilar pairs proves a universal frictional behaviour of superconductors below critical temperature T c. This effect can be considered as a general physical phenomenon. The existence of this general phenomenon in turn supposes that there is a unique physical mechanism determining the abnormal frictional behaviour of superconductors. The fact that small regions of contact area are periodically out of a superconducting state, completes the physical nature of ASF effect. The coexistence (or so-called “simbiosis”) of superconducting and normal states in a contact area is very important for the realization of ASF. The collapse of superconductivity in pair elements under the influence of a magnetic field usually results in supression. The requirement for the manifestation of the ASF effect is that T< T c and τ< τ′ where T and T c are the temperature and the critical temperature of superconducting transition of specimens, τ and τ′ are the relaxation times of the heat transfer processes into the helium and the heat conductivity into their bulk.