1 引 言 MgB2是20世纪50年代就早已熟悉的老材料，只是最近才发现它是超导体(Akimitsu, Nagamatsu et al 2001)，它具有简单六方结构，超导转变温度近40K。在BCS理论框架内，低质量元素产生较高频率的声子模，可导致更高的转变温度。过去曾有人预言，最轻的元素，氢，在高 1 Introduction MgB2 is an old material already familiar to the 1950s. It has only recently been discovered that it is a superconductor (Akimitsu, Nagamatsu et al. 2001). It has a simple hexagonal structure with a superconducting transition temperature of nearly 40K. In the framework of BCS theory, low-mass elements produce higher-frequency phonon modes that lead to higher transition temperatures. Someone in the past had predicted that the lightest element, hydrogen, was high