论文标题
轴承电荷密度波的时间转换不变的Weyl半学的动力压力磁效应
Dynamical Piezomagnetic Effect in Time-Reversal Invariant Weyl Semimetals with Axionic Charge-Density Waves
论文作者
论文摘要
Weyl半法（WSM）中的电荷密度波（CDW）已被证明会诱导一个外来的轴子绝缘阶段，在该阶段中，CDW的滑动模式（Phason）充当动力学轴向场，从而引起大型的正磁磁能传导[Wang等，Phys。，Phys。 Rev. B 87，161107（R）（2013）; Roy等人，物理。 Rev. B 92，125141（2015）; J. Gooth等人，自然575，315（2019）]。在这项工作中，我们预测动态应变会诱导由CDW覆盖的时间 - 反转（Tr-）不变的WSM中的散装轨道磁化。我们称这种效应为“动态压电效应”（DPME）。与[J. Gooth等人，Nature 575，315（2019）]，在这项工作中引入的DPME发生在散装组合（即散装中的静态和空间均匀）中，并且不依赖波动，例如phason。通过研究低能量有效理论和最小的紧密结合模型（TB）模型，我们发现DPME源自有效的山谷轴支球场，该场将电磁量规场与应变诱导的伪客场结合在一起。特别是，尽管以前工作中研究的压电效应的特征是2D浆果曲率，但DPME代表了源自Chern-Simons 3型的基本3D应变效应的第一个例子。我们进一步发现，DPME在CDW顺序参数阶段的临界值下具有不连续的变化。我们证明，当DPME中有跳跃时，系统的表面会经历拓扑量子相变（TQPT），而整体则保持不变。因此，DPME在TRINVARIANT WEYL-CDW中提供了边界TQPT的大量标志。
Charge-density waves (CDWs) in Weyl semimetals (WSMs) have been shown to induce an exotic axionic insulating phase in which the sliding mode (phason) of the CDW acts as a dynamical axion field, giving rise to a large positive magneto-conductance [Wang et al., Phys. Rev. B 87, 161107(R) (2013); Roy et al., Phys. Rev. B 92, 125141 (2015); J. Gooth et al., Nature 575, 315 (2019)]. In this work, we predict that dynamical strain can induce a bulk orbital magnetization in time-reversal- (TR-) invariant WSMs that are gapped by a CDW. We term this effect the "dynamical piezomagnetic effect" (DPME). Unlike in [J. Gooth et al., Nature 575, 315 (2019)], the DPME introduced in this work occurs in a bulk-constant (i.e., static and spatially homogeneous in the bulk) CDW, and does not rely on fluctuations, such as a phason. By studying the low-energy effective theory and a minimal tight-binding (TB) model, we find that the DPME originates from an effective valley axion field that couples the electromagnetic gauge field with a strain-induced pseudo-gauge field. In particular, whereas the piezoelectric effects studied in previous works are characterized by 2D Berry curvature, the DPME represents the first example of a fundamentally 3D strain effect originating from the Chern-Simons 3-form. We further find that the DPME has a discontinuous change at a critical value of the phase of the CDW order parameter. We demonstrate that, when there is a jump in the DPME, the surface of the system undergoes a topological quantum phase transition (TQPT), while the bulk remains gapped. Hence, the DPME provides a bulk signature of the boundary TQPT in a TR-invariant Weyl-CDW.
