Superconductivity of the Heterofullerides Synthesized from Gallams and Amalgams

Abstract

The fullerides with composition A2BxDyC60 (A=K,Rb,Cs; B,D=Ga, In, Sn, Bi, Be, Al, Mg, Hg; x,y<1) have been synthesized by using liquid amalgams (alloys of metals with mercury) or with an alloy of indium and gallium (gallams) at room temperature. It was found that the fulleride K2InxGayC60 is a superconductor with transition temperature Tc = 24.5 K that exceed Tc=19 K for reference K3C60. The fulleride Rb2InxGayC60 is a superconductor with Tc = 26 K. Superconductivity of heterofulleride with a composition K2HgxC60 (x<1) was observed at temperature Tc = 22 K. For the sample Rb2HgxC60 Tc=25 K, though Rb2C60, as well as K2C60, are not superconductors. Only one fulleride on the base of potassium (which does not include atoms of other alkaline metals Rb and Cs) was known before – the K2LuC60 (Tc=20 K) with Tc higher than for K3C60 [1]. The fullerides with composition Rb3InxGayC60 and Cs3InxGayC60 are not superconductors and crystallized in the orthorhombic lattice. Fullerides K2GaxBiyC60 and K2GaxSnyC60 (x,y<1) are superconductors.