| 报告题目 | Highly Anisotropic Dirac Fermions and their valley-polarized interlayer conduction in SrMnBi2 |
| 报告人 | Prof. Jun Sung Kim |
| 报告人单位 | Department of Physics, Pohang University of Science and technology |
| 报告时间 | 2014-01-07 |
| 报告地点 | 合肥微尺度物质科学国家实验室九楼会议室 |
| 主办单位 | 合肥微尺度物质科学国家实验室 |
| 报告介绍 | Abstract:
Since the discovery of high-Tc superconductivity in Fe-pnictides, layered pnictides have attracted a lot of attention as a new platform for inducing novel electronic states. In this talk, we report on a new bulk Dirac material SrMnBi2 that hosts highly anisotropic Dirac fermions in its Bi square net. Based on results from a first-principles calculation, quantum oscillations, and angle-resolved photoelectron spectroscopy on high-quality SrMnBi2 single crystals, we demonstrate that there is Dirac dispersion in the electronic structure of the double-sized Bi square net. In contrast to the graphene case, the Dirac cone in SrMnBi2 is highly anisotropic, showing a significant momentum-dependent Fermi velocity (vF) with a ratio between the maximum and minimum vF’s of ~ 10.
Using the anisotropic Dirac Fermi surfaceswith highly momentum-dependent warping, we found that the valley-polarized interlayer conduction can be realized in SrMnBi2 under tilted magnetic fields.Thec-axis resistivity of SrMnBi2 shows clear angle-dependent magnetoresistance oscillations indicatingcoherent interlayer conduction. Strong four-fold variation of the coherent peak with a rotatingin-plane magnetic field demonstrates that the contribution of each Dirac valley in the interlayerconduction is modulated by the field direction. This is based due to strong disparity in the interlayer coupling, which is intimately coupled to their anisotropic Fermi surface. Thesefindings demonstrate that the Bi square net, a common building block of various layered pnictide compounds, is a new platform for highly anisotropic Dirac fermions, which can hostvalley-polarized interlayer current through the magnetic valley control. |
