PtSe₂ is a recently discovered type-II Dirac semi-metal with heavily tilted Dirac cone in z-direction of the momentum. Negative magnetoresistance (MR) is expected as a signature of the chiral anomaly in the x–y plane where Lorentz invariance is maintained. Here we report the observation of negative MR in PtSe₂ thin flakes with magnetic fields aligned parallel to the current path and crystal a-axis. Systematic measurements reveal that this phenomenon is field-vector and temperature sensitive, thereby confirming chiral anomaly as its origin. Furthermore, the chiral anomaly is tunable with an electric field. Interestingly, negative MR vanishes along the orientation a′ perpendicular to a-axis. This clear anisotropy is ascribed to the anisotropic distribution of the Fermi velocity. A weaker chiral anomaly is caused in a′ and therefore masked by the trivial background signal. Our results highlight the importance of even a small material anisotropy when studying the chiral magnetotransport of Weyl/Dirac semi-metals.

PtSe ₂是最近发现的II型Dirac半金属，在动量的z方向上具有严重倾斜的Dirac锥。负磁阻（MR）有望作为保持劳伦兹不变性的x – y平面中手征异常的特征。在这里，我们报告在磁场平行于电流路径和晶体a轴排列的PtSe ₂薄片中观察到负MR 。系统测量表明，这种现象是场矢量和温度敏感的，从而证实了手性异常是其起源。此外，手性异常可通过电场来调节。有趣的是，负MR沿方向a消失垂直于a轴的′ 。这种明显的各向异性归因于费米速度的各向异性分布。较弱的手性异常是在引起一个“，因此由琐碎背景信号掩蔽。我们的结果凸显了在研究Weyl / Dirac半金属的手性磁传输时，即使材料各向异性很小的重要性。