Topic: Electrostatically defined hall bar in monolayer graphene
　　　　静电场定义的单层石墨烯霍尔条

Speaker: Shaowen Chen（陈少闻）^{1,2
　　　　　1} Department of Physics. 
² Department of Applied Physics and Applied Mathematics,Columbia University,
　　　　　New York, New York 10027, United States

Time: 15:00-16:30, (Tue.) Dec 19^th, 2017

Venue: Room 468，Lee Hsun Building, IMR CAS

Abstract:

Realizing graphene’s promise as an atomically thin and tunable platform for fundamental studies and future applications in quantum transport requires the ability to electrostatically define the geometry of the structure and control the carrier concentration, without compromising the quality of the system. Here we demonstrate the working principle of a new generation of high quality gate defined graphene samples, where the challenge of doing so in a gapless semiconductor is overcome by using the ν = 0 insulating state. Our devices demonstrate exceptionally high quality FQH effect with both well-developed two and four-flux states. Moreover, these devices permit the first experimental observation of reentrant quantum Hall effect in graphene, revealing the existence of electron solid states in higher Landau levels. This is the first time the electron solid state is observed in a system other than ultra high quality GaAs/AlGaAs quantum wells. The ability to electrostatically define conducting channels in graphene combined with the high quality of these new structures will enable the study of complex quantum transport phenomena, such as of fractional statistics, in a highly tunable material.