利用菲涅尔圆孔衍射探测AFeSe三元化合物超导配对对称性

提出了一个特殊菲涅尔圆孔衍射实验,核心由正常金属/绝缘层/超导体多层膜构成,用来精确探测超导配对对称性.理论分析表明,对于超导层是s波配对,△(-k)=△(k),且满足k·r=nπ的情况下,那么衍射图样的零阶为暗纹,其中k为波矢,n为整数.反之,如果△(-k)=-△(k),且在其他条件不变的情况下,那么零阶衍射图样为明纹.从而可以利用这种简单易行的实验途径,对超导电子的配对对称性进行无模棱两可的判定.最后把这套装置应用到最近发现的AFeSe三元化合物超导体,给出了可能的具体实验方案,来探测这种多费米面复杂的电子配对对称性.

Probing pairing symmetry of AFeSe superconductor using Fresnel aperture diffraction

A special Fresnel single aperture diffraction(FSAD) is proposed as a phase-sensitive probe to detect superconducting pairing symmetry.The instrument is built by a normal-insulator-superconductor junction.It is shown that in case of gap symmetry △(-k)=△(k) with k the wave vector of electrons tunneling into the trilayer,the quasiparticle FSAD pattern will developed at r a zeroth-order minimum if k·r=nπ (n is an integer).In contrast,for the case of △(-k)=-△(k),the corresponding FSAD pattern is zeroth-order maximum.This method is applied to the new found AFeSe superconductors.Some observable consequences and feasible experimental schemes are given further.