Superconductivity of twisted double bi-layer graphene in chiral model

Taking into account the sp -hybridization effect for valence electrons in carbon atoms, a very simple chiral model of graphene was suggested some years ago [1]. This model used as a special order parameter the unitary SU(2) -matrix U with the kink-like (or domain wall) structure for the description of electrons in a mono-atomic graphene sheet. However, later the new graphene physics began since studying twisted multilayer configurations revealing unconventional superconducting properties (twist-tronics) [2]. Within the scope of the chiral model these twisted configurations can be described by the so-called “product ansatz” U = U1U2 ▪ ▪ ▪ Un . As an example, the special case of twisted double bi-layer graphene (TDBG) configuration is studied and the corresponding twist angles, for which the superconductivity takes place, are found.