遷移金属カルコゲナイドナノチューブにおける量子輸送現象

今年，我们对在其他不同材料中产生这种固有二阶信号感兴趣，并开始研究其他主题。例如，在输运测量中，对称性使得二次谐波电压可以出现在横向，微观上的贡献之一是费米能级处能带结构的色散和动量空间中的Berry曲率分布。二次谐波电压的测量和对称性工程将是我们近期的目标。为了制作石墨烯异质结构，我们进一步发展了我们的转移技术，并在实验室引入了干拾取方法。此外，我们进行了偏振拉曼光谱，以便我们可以知道这两种材料的取向，从而精确地控制扭曲角。通过优化石墨烯异质结器件的制备工艺，我们最终获得了大尺寸（几十微米）的高质量石墨烯界面，可以同时进行输运和光学测量;最后，我们观察到了石墨烯异质结中的赝磁场效应，将原始石墨烯的朗道扇形图移动并复制为两个分支，受时间反转对称性的支配。其次，我们观察到了很好的量子霍尔态和很好的边缘输运现象。第三，在没有外加磁场的情况下，我们观察到了横向非线性信号，它来源于动量空间中费米面上的Berry曲率分布。

This year, we are interested in such intrinsic second order signal generation in other different materials and also start to work on other topics. For example, in transport measurement, the symmetry allows that the second harmonic voltage could appear in transvers direction, and one of the microscopically contribution is from both the dispersion of band structure at the Fermi energy and the Berry curvature distribution in the momentum space. Such measurement of second harmonic voltage and also the symmetry engineering will be our recent goal in the near future.In order to make graphene heterostructure, we have further developed our transfer technique and introduce dry pickup method in our lab. Furthermore, we carry out the polarized Raman spectrum and so that we could know the orientation of both materials and then precisely control the twisted angle. After optimize the fabrication process of graphene heterostructure device, we have finally achieve large size (tens micrometer size) high quality graphene interface, which can be measured by both transport and optics.Finally, we observed pseudo magnetic field effect in graphene heterostructure, the shifted and thus duplicated the Landau fan diagram of pristine graphene into two branches, governed by time reversal symmetry. Second, we observed pretty good quantum Hall state and good edge transport phenomena. Third, we observed nonlinear signal in transverse direction without external magnetic field, originated from Berry curvature distribution at the Fermi surface in the momentum space.