Hu Lun-Hui, Yu Jiabin, Garate Ion, Liu Chao-Xing
Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742, USA.
Phys Rev Lett. 2021 Sep 17;127(12):125901. doi: 10.1103/PhysRevLett.127.125901.
In two-dimensional insulators with time-reversal (TR) symmetry, a nonzero local Berry curvature of low-energy massive Dirac fermions can give rise to nontrivial spin and charge responses, even though the integral of the Berry curvature over all occupied states is zero. In this Letter, we present a new effect induced by the electronic Berry curvature. By studying electron-phonon interactions in BaMnSb_{2}, a prototype two-dimensional Dirac material possessing two TR-related massive Dirac cones, we find that the nonzero local Berry curvature of electrons can induce a phonon angular momentum. The direction of this phonon angular momentum is locked to the phonon propagation direction, and thus we refer to it as "phonon helicity" in a way that is reminiscent of electron helicity in spin-orbit-coupled electronic systems. We discuss possible experimental probes of such phonon helicity.
在具有时间反演（TR）对称性的二维绝缘体中，低能大质量狄拉克费米子的非零局域贝里曲率可引发非平凡的自旋和电荷响应，即便贝里曲率在所有占据态上的积分值为零。在本信函中，我们展示了一种由电子贝里曲率引发的新效应。通过研究具有两个与TR相关的大质量狄拉克锥的二维狄拉克材料原型BaMnSb₂中的电子 - 声子相互作用，我们发现电子的非零局域贝里曲率可诱导出声子角动量。该声子角动量的方向锁定在声子传播方向上，因此我们以类似于自旋轨道耦合电子系统中电子螺旋度的方式将其称为“声子螺旋度”。我们讨论了这种声子螺旋度可能的实验探测方法。
