报告题目：A Perfect Electron Storm in Nanoscale

报 告 人：Jun YUAN, Department of Physics, University of York, U.K.

报告时间：10月25日（周四）11:00-11:45

报告地点：物理系三楼报告厅

报告摘要：A vortex is a common phenomenon in daily life, from a whirlpool in a stirred coffee cup to the eye of storms in the summer typhoon season. In this talk, I will introduce a new kind of electron beam with spiral wavefronts, called electron vortex beam. Like typhoons, it has an ‘eye’ of zero transverse phase velocity at its axis. Quantum mechanically, such a beam carries well-defined orbital angular momentum. I will show how vortex beams can be produced at nanoscale and characterized. I will then discuss the interaction of such beams with atoms. Compared with optical vortex beams that have been studied intensively for more than a decade, electron vortex beams can transfer one unit of orbital angular momentum to the atom’s internal degree of motion following a dipole transition, opening ways for chiral-sensitive spectroscopy to be developed. Finally, I will demonstrate an ‘electron spanner effect’, the transfer of orbital angular momentum to the center of mass of the atoms, by showing reversible rotation of gold nanoparticles depending on the chirial charge of the vortex beam applied.