论文标题
石墨烯中高谐波产生的掺杂和间隙大小的依赖性：一致配方的重要性
Doping and gap-size dependence of high-harmonic generation in graphene : Importance of consistent formulation of light-matter coupling
论文作者
论文摘要
固体中的高谐波生成（HHG）是一种基本的非线性现象，可以通过修改系统参数（例如掺杂级别和温度）来有效控制。为了正确预测HHG对这些参数的依赖性，光 - 耦合的一致理论表述至关重要。最近，已经指出了基于半导体Bloch方程的HHG分析中经常缺少的电流的贡献[J.威廉等人PRB 103 125419（2021）]。在本文中，通过系统地分析HHG在Gapped石墨烯中的掺杂和间隙尺寸依赖性，我们讨论了此类术语的实际影响。特别是，我们专注于当前$ j _ {\ rm ra}^{（2）} $的角色，该角色源自通过边界间过渡的内标偶极子的更改。当差距很小并且系统接近一半填充时，内标和间电流大多取消，从而抑制了HHG信号 - 当忽略$ j _ {\ rm ra}^{（2）} $时，它是一种重要的属性。此外，如果没有$ j _ {\ rm ra}^{（2）} $，HHG的掺杂和间隙大小的依赖性与完整评估在质上不同。我们的结果表明，电流表达的重要性对于研究HHG对小间隙系统的参数依赖性的重要性。
High-harmonic generation (HHG) in solids is a fundamental nonlinear phenomenon, which can be efficiently controlled by modifying system parameters such as doping-level and temperature. In order to correctly predict the dependence of HHG on these parameters, consistent theoretical formulation of the light-matter coupling is crucial. Recently, contributions to the current that are often missing in the HHG analysis based on the semiconductor Bloch equations have been pointed out [J. Wilhelm, et.al. PRB 103 125419 (2021)]. In this paper, by systematically analyzing the doping and gap-size dependence of HHG in gapped graphene, we discuss the practical impact of such terms. In particular, we focus on the role of the current $J_{\rm ra}^{(2)}$, which originates from the change of the intraband dipole via interband transition. When the gap is small and the system is close to half filling, intraband and interband currents mostly cancel, thus suppressing the HHG signal - an important property that is broken when neglecting $J_{\rm ra}^{(2)}$. Furthermore, without $J_{\rm ra}^{(2)}$, the doping and gap-size dependence of HHG becomes qualitatively different from the full evaluation. Our results demonstrate the importance of the consistent expression of the current to study the parameter dependence of HHG for the small gap systems.
