Localization and mass spectrum of spin-1/2 fermionic field on a thick brane with Poincare symmetry

We investigate localization and mass spectrum of spin-1/2 fermionic field on a scalar thick brane configuration with Poincare symmetry, which arises in a 5-dimensional theory of gravity coupling to a self-interacting scalar field in a regular Riemannian manifold. It is shown that, in the case of no Yukawa coupling of scalar-fermion, there is no existence of localized massless zero mode for both left and right chiral fermions. By introducing appropriate coupling, we can obtain the localized modes as well as a continuous spectrum of massive Kaluza-Klein (KK) modes for left and right chiral fermions. It is found that there exists a mass gap between the massless zero mode and the excited modes for left chiral fermions or right chiral fermions. The total number of bound states is determined by the Yukawa coupling constant and the parameter of the thick brane solution. Depending on the sign of the coupling constant, only one category of zero modes, namely, either the left or right chiral zero mode can be trapped on the brane. Copyright (C) EPLA, 2009