Ab initio study of angle-resolved electron reflection spectroscopy of few-layer graphene
Aleš Paták, Martin Zouhar, Ivo Konvalina, Eliška Materna Mikmeková, Lukáš Průcha, Ilona Müllerová, Anna Charvátová Campbell, Miroslav Valtr, Michal Horák, Vlast… 展开作者
Aleš Paták, Martin Zouhar, Ivo Konvalina, Eliška Materna Mikmeková, Lukáš Průcha, Ilona Müllerová, Anna Charvátová Campbell, Miroslav Valtr, Michal Horák, Vlastimil Křápek, Eugene Krasovskii
We present ab initio theory for electron reflection spectroscopy of few-layer graphene for arbitrary angles of incidence. The inelastic effects are included in a consistent way using the optical potential retrieved from ab initio simulations of electron energy-loss spectra. We demonstrate a significant impact of inelastic effects even for single-layer graphene. Next, we address the ability of the electron reflection spectroscopy to determine specific parameters of graphene including not only the number of layers in the few-layer graphene but also the stacking type in the graphene multilayers, and to resolve moiré patterns in twisted graphene bilayers. We show that the predicted contrast, although significantly reduced by inelastic effects, is sufficient for the experimental detection of all considered parameters. Our findings are corroborated by a fair correspondence of our theoretical predictions with experimental data, both our own and recently published by other authors.
We investigate how parameters of the model of semi-infinite graphene based on a graphene nanoribbon under periodic boundary conditions affect the accuracy of ab initio calculations of reactions at graphene edges by the example of the first stage of reconstruction of zigzag graphene edges, formation of a pentagon-heptagon pair. It is shown that to converge properly the results, the nanoribbon should consist of at least 6 zigzag rows and periodic images of the pair along the nanoribbon axis should be separated by at least 6 hexagons. The converged reaction energy and activation barrier for forma…
Electronic Structure and Transport in Graphene/Haeckelite Hybrids: An {\em Ab Initio} Study
我们结合{ \em ab initio}密度泛函理论（DFT）的结构研究与DFT为基础的非平衡格林函数计算，探讨非六方环的存在如何影响石墨结构中的电子输运。我们发现，无限的单层，有限宽度的纳米带和纳米管形成的5-8 haeckelite只有5-和8-元环通常比他们的石墨烯为基础的同行更导电。完美的石墨结构中存在的海克石缺陷线，CVD生长的石墨烯中的晶界的模型，增加了电子导电性，并使其高度各向异性。
There has been a lot of excitement around the observation of superconductivity in twisted bilayer graphene, associated to flat bands close to the Fermi level. Such correlated electronic states also occur in multilayer rhombohedral stacked graphene (RG), which has been receiving increasing attention in the last years. In both natural and artificial samples however, multilayer stacked Bernal graphene (BG) occurs more frequently, making it desirable to determine what is their relative stability and under which conditions RG might be favored. Here, we study the energetics of BG and RG in bulk and …
The newly realized twisted graphene systems such as twisted bilayer graphene (TBG), twisted double bilayer graphene (TDBG), and twisted trilayer graphene (TTG) have attracted widespread theoretical attention. Therefore, a simple and accurate model of the systems is of vital importance for the further study. Here, we construct the symmetry-adapted localized Wannier functions and the corresponding $\textit{ab initio}$ minimal two-valley four-band effective tight-binding models for generic twisted graphene systems with small twist angle. Such two-valley model evades the Wannier obstruction caused…
The potential energy surface (PES) of interlayer interaction of twisted bilayer graphene with vacancies in one of the layers is investigated via density functional theory (DFT) calculations with van der Waals corrections. These calculations give a non-negligible magnitude of PES corrugation of 28 meV per vacancy and barriers for relative sliding of the layers of 7 - 8 meV per vacancy for the moiré pattern with coprime indices (2,1) (twist angle 21.8$^\circ$). At the same time, using the semiempirical potential fitted to the DFT results, we confirm that twisted bilayer graphene without defects …
Ab initio calculation of the $G$ peak intensity of graphene: Combined study of the laser and Fermi energy dependence and importance of quantum interference effects
Angle-Dependent {\it Ab initio} Low-Energy Hamiltonians for a Relaxed Twisted Bilayer Graphene Heterostructure
基于力学和电子结构的{ \it ab initio}计算，提出了描述扭曲双层石墨烯（tBLG）异质结构性质的有效的角度依赖低能哈密顿量.依赖于角度的弛豫原子几何形状由连续弹性理论确定，其在堆叠的石墨烯层中引起面内和面外变形。对应于变形的几何形状的电子性质来自于从密度泛函理论计算获得的局部相互作用的Wannier变换。利用这些弛豫异质结构的{ \it ab initio}紧束缚哈密顿量，从狄拉克锥附近K谷的投影导出了低能有效理论.对于扭转角从0.7 $^\circ$到4 $^\circ$的情况，我们提取了低能哈密顿量中的层内赝规范场和层间耦合项，扩展了传统的低能连续介质模型.我们进一步包括动量依赖层间散射项，引起的电子结构的粒子-空穴不对称功能。我们的模型哈密顿可以作为一个起点，制定物理意义，准确的相互作用电子理论。
We perform a detailed analysis of electronic polarizability of graphene with different theoretical approaches. From Kubo's linear response formalism, we give a general expression of frequency and wave-vector dependent polarizability within the random phase approximation. Four theoretical approaches have been applied to the single-layer graphene and their differences are on the band-overlap of wavefunctions. By comparing with the \textit{ab initio} calculation, we discuss the validity of methods used in literature. Our results show that the tight-binding method is as good as the time-demanding …
