Abstract :   It is demonstrated that the quantum phase transition between the gap and gapless  superconducting states in the Abrikosov-Gor'kov theory of superconducting alloy with paramagnetic impurities is of the Lifshitz type, i.e. of the 2 1#2 order. This phase transition has a topological nature and is characterized by the corresponding change of the topological invariant, namely the Euler characteristic. We study the stability of such a transition with respect to the spatial fluctuations of the magnetic impurities critical concentration ?! and show that the requirement for validity of its mean field description is unobtrusive: ∇ ln(?!) ≪ ?"#(here ? is the superconducting coherence length). Finally, we show that, similarly to the Lifshitz point, the 2 1#2 order phase transition should be accompanied by the corresponding singularities, for instance, the superconducting thermoelectric effect has a giant peak exceeding the normal value of the Seebeck coefficient by the ratio of the Fermi energy and the superconducting gap.

主讲人简介：安德烈·瓦尔拉莫夫（Andrey Varlamov）教授是超导理论和凝聚态物理学领域的著名科学家，1980年在阿历克斯·阿布里科索夫（2003年获诺贝尔物理学奖得主）指导下获凝聚态物理学博士学位，1986年获苏联国家青年科学家物理学奖，1990～1999任莫斯科钢铁与合金研究所理论物理系教授；1999年起任意大利国家研究委员会超导、新材料和器件研究所研究主任，罗马大学教授；2009年起任意大利科学院通讯院士；有8本超导理论方面的专著和130余篇科学论文；已有50余篇科普作品发表于《量子》等著名科普刊物，主要由这些科普作品结集成书的《奇妙的物理学》，自1987年面世以来，以6种语言出版了12版，直接影响了世界各国的科普读者。