论文标题
非线性运输，无自旋轨道耦合或旋转二维狄拉克半米
Non-linear transport without spin-orbit coupling or warping in two-dimensional Dirac semimetals
论文作者
论文摘要
最近已经意识到，浆果曲率的第一阶矩，即浆果曲率偶极子（BCD）可以在多种时间不变和非中心含量的材料中引起非线性电流。虽然已知二维Dirac系统中的BCD仅在存在实质性的旋转轨道耦合的情况下才是有限BCD。值得注意的是，在这样的系统中，BCD被发现独立于Dirac速度，而不是具有倾斜或翘曲效果的狄拉克分散体。我们进一步表明，由于其线性动量依赖性浆果曲率，提出的系统可以自然构成螺旋依赖性光电流。最后，我们讨论了这项工作的重要副产品，即非线性异常的Nernst效应作为二阶热响应。
It has recently been realized that the first-order moment of the Berry curvature, namely the Berry curvature dipole (BCD) can give rise to non-linear current in a wide variety of time-reversal invariant and non-centrosymmetric materials. While the BCD in two-dimensional Dirac systems is known to be finite only in the presence of either substantial spin-orbit coupling where low-energy Dirac quasiparticles form tilted cones or higher order warping of the Fermi surface, we argue that the low-energy Dirac quasiparticles arising from the merging of a pair of Dirac points without any tilt or warping of the Fermi surface can lead to a non-zero BCD. Remarkably, in such systems, the BCD is found to be independent of Dirac velocity as opposed to the Dirac dispersion with a tilt or warping effects. We further show that the proposed systems can naturally host helicity-dependent photocurrent due to their linear momentum-dependent Berry curvatures. Finally, we discuss an important byproduct of this work, i.e., nonlinear anomalous Nernst effect as a second-order thermal response.
