title: Finite size effects on helical edge states in a quantum spin-Hall system.
abstract: The hallmark of the spin-Hall insulator is the presence of gapless edge states of different spins moving in opposite directions. Through analytical solutions in a model calculation for a strip of finite width, we find that edge states on the two sides can couple together to produce a gap in the spectrum, destroying the quantum spin-Hall effect. The application of a magnetic field can however modify and even remove the gap by shifting the momenta of the edge states relative to each other.
authors.affiliation: Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Zhou
authors.forename: Hai-Zhou
authors.initials: HZ
authors.lastname: Lu
authors.forename: Rui-Lin
authors.initials: RL
authors.lastname: Chu
authors.forename: Shun-Qing
authors.initials: SQ
authors.lastname: Shen
authors.forename: Qian
authors.initials: Q
authors.lastname: Niu