Bound states of Schrödinger type operators with Heisenberg sub-Laplacian

Using the technique from \[8] we find a new constant in a Cwikel–Lieb–Rozenblum type inequality that estimate the number of negative eigenvalues of a Schrödinger operator involving the Heisenberg sub-Laplacian with a potential that is proportional to the characteristic function of a measurable set.