论文标题
间隙和无间隙超导状态之间过渡的拓扑性质
Topological nature of the transition between the gap and the gapless superconducting states
论文作者
论文摘要
最近证明，在Abrikosov-Gor'kov与副磁性杂质的超导合金理论中，间隙和无间隙超导状态之间的悠久已知过渡是Lifshitz的类型，即在零温度下，这是$ 2 \ frac12 $ frac12 $订单相位过渡。由于这种在正常金属中的过渡始终与某些拓扑变化有关，因此我们在下面阐明了所考虑的过渡的拓扑性质。也就是说，我们证明，在过渡过程中发生变化的拓扑不变不过是欧拉的特征。另外，就灾难理论而言，可以将这种过渡与状态密度相应表面的尖边的外观联系起来，这是能量和超导顺序参数的功能。提出了确认$ 2 \ frac12 $订单拓扑相变的实验概念。 Obtained theoretical results can be applied for the explanation of recent experiments with lightwave-induced gapless superconductivity, for the interpretation of the disorder induced transition $s_{\pm}$-$s_{++}$ states via gapless phase in two-band superconductors, and the emergence of gapless color superconductivity in quantum chromodynamics.
Recently it was demonstrated that the long-known transition between the gap and gapless superconducting states in the Abrikosov-Gor'kov theory of superconducting alloy with paramagnetic impurities is of the Lifshitz's type, i.e. at zero temperature this is the $2\frac12$ order phase transition. Since transitions of this kind in a normal metal are always associated to certain topological changes, then below we clarify the topological nature of the transition under consideration. Namely, we demonstrate that the topological invariant which in process of the transition undergoes the change is nothing but the Euler characteristic. Alternatively, in terms of the theory of catastrophes one can relate this transition to appearance of the cuspidal edge at the corresponding surface of the density of states as the function of energy and superconducting order parameter. The concept of experiments for the confirmation of $2\frac12$ order topological phase transition is proposed. Obtained theoretical results can be applied for the explanation of recent experiments with lightwave-induced gapless superconductivity, for the interpretation of the disorder induced transition $s_{\pm}$-$s_{++}$ states via gapless phase in two-band superconductors, and the emergence of gapless color superconductivity in quantum chromodynamics.
