题　目：Dirac Cone Dispersions in Classical Systems and Their Implications
报告人：陈子亭博士（香港科技大学物理系首席教授）
时　间：12月14日（周五），上午10：30-11：30
地　点：瑞安楼二楼报告厅

Abstract：
Many unusual properties of graphene can be traced to its singular band structure near the Fermi level where two cones meet at one point. Such a dispersion is called a Dirac cone dispersion and the singular point the Dirac point. Dirac cone like dispersions are not unique to electronic graphene, but can also be found in many classical wave systems at the zone boundary as a consequence of lattice symmetry. In this talk, I will explore the consequence of having Dirac cone like dispersions at k=0. We show that Dirac cone like dispersions at k=0 can be obtained in classical wave systems using accidental degeneracy. If the photonic band dispersions originates from monopole and dipole excitations, such dispersions can be related to a double zero (zero permittivity and zero permeability) material at and near the Dirac point frequency in the sense that the system behave optically as if the refractive index is zero. From an effective medium point of view, such system has an infinite phase velocity but a finite group velocity. We will consider the extension of these ideas to from two dimensions to three dimensions and from periodic to aperiodic systems.

简历：陈子亭，香港科技大学高等研究院执行院长，物理系讲席教授，香港William Mong 纳米技术研究所所长。于1980年在香港大学获得本科学位，1985年在加州大学伯克利分校获得博士学位，之后在美国衣阿华州埃姆斯(Ames)国家实验室工作，1995年到香港科技大学任教。长期从事材料物性方面的研究，涉及光子晶体、超材料、表面等离激元光学材料以及半导体等微纳介观体系和电子学材料等。在Science、Nature、PRL等刊物上发表文章约200篇，他引次数14，000多次，h-index>60。目前在多个大学、研究所和研究机构的学术委员会、期刊编委任职。获得美国能源部颁发的杰出贡献奖（1992），入选美国物理学会理事（1996）、获得麦考盖勒杰出教学金奖（1999）、海外华人物理学亚洲杰出贡献奖（2000）、电磁科学院理事（2004）、科罗索高级研究理事（2010）。