Abstract
A Weyl semimetal is a kind of special crystal which has Weyl fermions and exhibits Fermi arcs on its surface. A Dirac point is composed of two Weyl nodes which have opposite chirality, and act as magnetic monopoles. Based on the quantum field theory, the emergence of Weyl nodes near the Fermi level induces novel transport phenomena related to chiral anomaly, which can be understood as the non-conservation of the particle number with given chirality. The anomaly shows up only when the magnetic field is parallel to the electric field. In this work we studied the physical properties of TaAs Weyl semimetal. The crystallographic c-axis which is perpendicular to the surface of TaAs single crystal is confirmed by the result of XRD. The transport properties of TaAs is measured by the physical properties measurement system (PPMS). The temperature dependence of resistivity demonstrates that TaAs is metallic at zero magnetic field, and it then changes from metal to insulator when magnetic field increases form 0 tesla to 9 tesla. The measurement results present evidences that the negative magneto-resistance is generated by the chiral anomaly in a predicted time reversal symmetry in Weyl semimetal TaAs. In the measurements of magnetic field dependence of Seebeck coefficient, the difference of magneto-Seebeck is observed when magnetic field is parallel and perpendicular to the temperature gradient. In general, the behavior of Seebeck coefficient is similar to that of magneto-resistance. At low magnetic field, the Seebeck coefficient and magneto-resistance show weak anti-localization behavior, both increase as magnetic field rises. When the direction of magnetic field changes from parallel ( B∥T) to perpendicular (B⊥T) with respect to the temperature gradient, the magnitude of Seebeck coefficient increases from -1.5 to -13μV/K, whereas the negative sign represents TaAs is p - type Weyl semimetal.