铋锑合金中Weyl费米子的磁输运性质研究

The magnetic transport properties of Weyl fermions in BiSb alloys

铋锑合金(Bi1-xSbx)的能带结构随x而变化,在拓扑绝缘体和拓扑半金属的研究中具有重要的地位。对Bi0.96Sb0.04的研究表明,该合金的电阻率随温度的升高先升后降,具有典型的半金属特点。在极低温度下可以观察到纵向磁电阻和横向霍尔电阻随外磁场的Shubnikov de Haas振荡,且两者的振荡相位正好相反。随磁场增加的不饱和线性磁电阻可以解释为在具有无能隙或极小能隙材料中,费米面附近电子线性色散关系带来的量子效应。在低温下,通过外加磁场可使简并的Dirac锥电子,分离成不同手性的Weyl电子,在磁场方向与电流方向一致时观察到了手性反常引起的负磁电阻效应。

The BiSb alloy is of special significance in topological insulator research.Here we focus on Bi0.96Sb0.04 alloy in which the conduction band edge just touches the valence band edge.First increasing and then decreasing of the resistance of Bi0.96Sb0.04 alloy shows its typical semimetal behavior.Transport measurement shows that the Shubnikov de Haas oscillation occurs in longitudinal magnetoresistance and transverse Hall resistance with opposite phase.Further investigation of longitudinal magnetoresistance(MR)shows that when magnetic field B is along with the electric current,the longitudinal magnetoresistance is negative at some magnetic field from 0.5 to 1.5 T,which is resulted from the chiral anomaly of Weyl fermions splitted from dirac cone by the magnetic field.More interestingly,the negative part of the longitudinal MR is not just a monotonic decrease,but with a kind of oscillation.This could be an approach for acquiring Weyl Fermions and Weyl semimetals in Bi0.96Sb0.04 single crystal alloy.