论文标题
对山谷密度的不保守及其对观察山谷效应的影响
Non-conservation of the valley density and its implications for the observation of the valley Hall effect
论文作者
论文摘要
我们表明，驱动山谷大厅效应的电场以出乎意料的方式打破了多瓦利绝缘子中山谷密度的保护。这意味着时间逆转不变的完全间隙的绝缘子，其中没有散装或边缘状态越过费米水平，可以支撑散装的山谷大厅电流，但在边缘没有山谷密度的积累。因此，在这样的系统中无法观察到山谷大厅的效应。如果系统没有完全盖布，则可能在边缘处积累谷地密度。累积没有从地下状态的贡献，可以表示为费米表面的平均值，我们为此得出明确的公式。我们通过计算谷数谷霍尔孔绝缘子中的山谷密度积累来证明理论：一种张开的石墨烯纳米苯。令人惊讶的是，我们发现，针对某些边缘终止，净谷密度极化是动态生成的。
We show that the conservation of the valley density in multivalley insulators is broken in an unexpected way by the electric field that drives the valley Hall effect. This implies that time-reversal-invariant fully gapped insulators, in which no bulk or edge state crosses the Fermi level, can support a valley Hall current in the bulk and yet show no valley density accumulation at the edges. Thus, the valley Hall effect cannot be observed in such systems. If the system is not fully gapped then valley density accumulation at the edges is possible. The accumulation has no contribution from undergap states and can be expressed as a Fermi surface average, for which we derive an explicit formula. We demonstrate the theory by calculating the valley density accumulations in an archetypical valley-Hall insulator: a gapped graphene nanoribbon. Surprisingly, we discover that a net valley density polarization is dynamically generated for certain edge terminations.
