Electron states for gapped pseudospin-1 fermions in the field of a charged impurity

EV Gorbar, VP Gusynin, DO Oriekhov - Physical Review B, 2019 - APS
Physical Review B, 2019APS
The electron states of gapped pseudospin-1 fermions of the α− T 3 lattice in the Coulomb
field of a charged impurity are studied. The free α− T 3 model has three dispersive bands
with two energy gaps between them depending on the parameter Θ which controls the
coupling of atoms of a honeycomb lattice with atoms in the center of each hexagon, thus
interpolating between graphene Θ= 0 and dice model Θ= π/4. The middle band becomes a
flat one with zero energy in the dice model. The bound electron states are found in the two …
The electron states of gapped pseudospin-1 fermions of the lattice in the Coulomb field of a charged impurity are studied. The free model has three dispersive bands with two energy gaps between them depending on the parameter which controls the coupling of atoms of a honeycomb lattice with atoms in the center of each hexagon, thus interpolating between graphene and dice model . The middle band becomes a flat one with zero energy in the dice model. The bound electron states are found in the two cases: the centrally symmetric potential well and a regularized Coulomb potential of the charged impurity. As the charge of the impurity increases, bound-state energy levels descend from the upper and central continua and dive at certain critical charges into the central and lower continuum, respectively. In the dice model, it is found that the flatband survives in the presence of a potential well, however, is absent in the case of the Coulomb potential. The analytical results are presented for the energy levels near continuum boundaries in the potential well. For the genuine Coulomb potential, we present the recursion relations that determine the coefficients of the series expansion of wave functions of bound states. It is shown that the condition for the termination of the series expansion gives two equations relating energy and charge values. Hence, analytical solutions can exist for a countably infinite set of values of impurity charge at fixed .
American Physical Society
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