We consider a single layer graphene nanoribbon with armchair edges in a longitudinally constant external potential and point out that its transport properties can be described by means of an effective non-Hermitian Hamiltonian. We show that this system has some features typical of dissipative systems, namely the presence of exceptional points and of PT-symmetry breaking, although it is not dissipative.

http://arxiv.org/abs/1102.2129v1
Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Quantum Physics (quant-ph)