The new representation is at the very end of their paper: <a href="https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.132.221601" rel="nofollow">https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.132.221...</a><p>How does the n-1 subscript on the second parentheses work?