Soliton trap in strained graphene nanoribbons

The wavefunction of a massless fermion consists of two chiralities, left handed and right handed, which are eigenstates of the chiral operator. The theory of weak interactions of elementary particle physics is not symmetric about the two chiralities, and such a symmetry-breaking theory is referred to as a chiral gauge theory. The chiral gauge theory can be applied to the massless Dirac particles of graphene. In this paper, we show within the framework of the chiral gauge theory for graphene that a topological soliton exists near the boundary of a graphene nanoribbon in the presence of a strain. This soliton is a zero-energy state connecting two chiralities and is an elementary excitation transporting a pseudo-spin. The soliton should be observable by means of a scanning tunneling microscopy experiment.