Superconductivity in two-dimensional disordered Dirac semimetals
Superconductivity in two-dimensional disordered Dirac semimetals
复制标题
二维无序狄拉克半金属的超导性
DOI：
10.1103/physrevb.95.054507
复制
发表时间：
2016-04
影响因子：
3.7
通讯作者：
Guo-Zhu Liu
中科院分区：
文献类型：
--
作者：
Jing Wang;Peng-Lu Zhao;Jing-Rong Wang;Guo-Zhu Liu
在二维狄拉克半金属中，库珀配对不稳定性只发生在吸引相互作用强度|u| $大于某个临界值$|联系我们|因为态密度在狄拉克点为零。无序增强了低能态密度，但同时缩短了费米子的寿命，这分别倾向于促进和抑制超导电性。为了确定哪一个竞争效应获胜，我们研究的库珀配对相互作用和无序散射的重正化群方法的相互作用。我们考虑三种类型的障碍，包括随机质量，随机规范势，和随机化学势，并表明，前两个抑制超导性。特别是临界BCS耦合$|联系我们|当系统只含有随机质量或随机规范势时，$增大到某个较大的值，这使得超导性的发生更加困难。在随机化学势的情况下，有效的无序参数流到强耦合区，在那里微扰展开破裂，不能提供一个明确的答案有关的超导性的命运。当不同类型的无序共存于一个系统中时，它们的强度参数都流向强耦合。在强耦合区，微扰重整化群方法变得无效，需要采用其他方法来处理无序效应。利用Abrikosov-Gorkov图解方法，对随机化学势对超导性的影响进行了简单的能隙方程分析，并简要讨论了这种方法的可能推广。
In two-dimensional Dirac semimetals, Cooper pairing instability occurs only when the attractive interaction strength $|u|$ is larger than some critical value $|{u}_{c}|$ because the density of states vanishes at Dirac points. Disorders enhance the low-energy density of states but meanwhile shorten the lifetime of fermions, which tend to promote and suppress superconductivity, respectively. To determine which of the two competing effects wins, we study the interplay of Cooper pairing interaction and disorder scattering by means of renormalization group method. We consider three types of disorders, including random mass, random gauge potential, and random chemical potential, and show that the first two suppress superconductivity. In particular, the critical BCS coupling $|{u}_{c}|$ is increased to certain larger value if the system contains only random mass or random gauge potential, which makes the onset of superconductivity more difficult. In the case of random chemical potential, the effective disorder parameter flows to the strong coupling regime, where the perturbation expansion breaks down and cannot provide a clear answer concerning the fate of superconductivity. When different types of disorder coexist in one system, their strength parameters all flow to strong couplings. In the strong coupling regime, the perturbative renormalization group method becomes invalid, and one needs to employ other methods to treat the disorder effects. We perform a simple gap equation analysis of the impact of random chemical potential on superconductivity by using the Abrikosov-Gorkov diagrammatic approach, and also briefly discuss the possible generalization of this approach.