Title: Excitonic mass gap in uniaxially strained graphene,
Abstract: We study the conditions for spontaneously generating an excitonic mass gap
due to Coulomb interactions between anisotropic Dirac fermions in uniaxially
strained graphene. The mass gap equation is realized as a self-consistent
solution for the self-energy within the Hartree-Fock mean-field and static
random phase approximations. It depends not only on momentum, due to the
long-range nature of the interaction, but also on the velocity anisotropy
caused by the presence of uniaxial strain. We solve the nonlinear integral
equation self-consistently by performing large scale numerical calculations on
variable grid sizes. We evaluate the mass gap at the charge neutrality (Dirac)
point as a function of the dimensionless coupling constant and anisotropy
parameter. We also obtain the phase diagram of the critical coupling, at which
the gap becomes finite, against velocity anisotropy. Our numerical study
indicates that with an increase in uniaxial strain in graphene the strength of
critical coupling decreases, which suggests anisotropy supports formation of
excitonic mass gap in graphene.