Interface modulated electron mobility enhancement in core-shell nanowires

The transport properties of core-shell nanowires (CSNWs) under interface modulation and confinement are investigated based on the atomic-bond-relaxation (ABR) correlation mechanism and Fermi's golden rule. An analytical expression for the relationship between carrier mobility and interface mismatch strain is derived and the influence of size, shell thickness and alloyed layer on effective mass, band structures, and deformation potential constant are studied. It is found that interface modulation can not only reduce the lattice mismatch to optimize the band alignment, but also participate in the carrier transport for enhancing mobility. Moreover, the underlying mechanism regarding the interface shape dependence of transport properties in CSNWs is clarified. The great enhancement of electron mobility suggests that the interface modulation may become a potential pathway to improving the performance of nanoelectronic devices.     

分光计调节中的难点分析及调节方法的改进

针对分光计调节过程中可能遇到的难点,给出了相应的解决方法:采用极限调节法寻找十字像;在使用各半调节法调节载物台上的螺钉时,不再限定螺钉的选择,可以只使用一个螺钉,也可以两个螺钉交替使用,提出了"双自由选择法";载物台转动180°之后找不到十字像的情况下,提出将载物台面降到最低的方法即"回归初始状态法";载物台转动90°之后,在第三颗螺钉已经处于极限位置并且还需要调节的情况下,采用"相对位置改变法",同时升高(或降低)另外两个螺钉的方法,简单有效地解决了问题。经过实验验证所提方法能够有效地提高分光仪的调节速率。     

Optical conductivity of twisted bilayer graphene near the magic angle

We theoretically study the band structure and optical conductivity of twisted bilayer graphene(TBG) near the magic angle considering the effects of lattice relaxation. We show that the optical conductivity spectrum is characterized by a series of peaks associated with the van Hove singularities in the band structure, and the peak energies evolve systematically with the twist angle. Lattice relaxation effects in TBG modify its band structure, especially the flat bands, which leads to significant shifts of the peaks in the optical conductivity. These results demonstrate that spectroscopic features in the optical conductivity can serve as fingerprints for exploring the band structure, band gap, and lattice relaxation in magic-angle TBG as well as identifying its rotation angle.     

Quantum Correlation Coefficients for Angular Coherent States

Quantum covariance and correlation coefficients of angular or SU（2） coherent states are directly calculated for all irreducible unitary representations. These results explicitly verify that the angular coherent states minimize the Robertson-Schrodinger uncertainty relation for all spins, which means that they are the so-called intelligent states. The same results can be obtained by the Schwinger representation approach.