Can any body suggests that hopping terms can be t times exp(i^*phi),where phi is any value,we like .Is it possible that we can keep the value like this,what it means physics wise .
t is the hopping energy between carbon-carbon atoms, a constant. phi is not necessarily 'any value we like' but it is the projection betwee the wave number k and the lattice constant.
It depends on what you are studying. the hopping terms may vary upon the introduction of external fields.
Physics-wise, it means that we assume that the wave functions are orthogonal during hopping.
If you will, kindly read this publication attached:
Thanks
Article Generalized tight-binding transport model for graphene nanor...