arXiv:1509.06861 · Physical review. B./Physical review. B
Spectral function of the Tomonaga-Luttinger model revisited: Power laws and universality
L Markhof, V. Meden
Abstract
We reinvestigate the momentum-resolved single-particle spectral function of the Tomonaga-Luttinger model. In particular, we focus on the role of the momentum dependence of the two-particle interaction $V(q)$. Usually, $V(q)$ is assumed to be a constant and integrals are regularized in the ultraviolet ``by hand'' employing an ad hoc procedure. As the momentum dependence of the interaction is irrelevant in the renormalization group sense, this does not affect the universal low-energy properties of the model, e.g., exponents of power laws, if all energy scales are sent to zero. If, however, the momentum $k$ is fixed away from the Fermi momentum ${k}_{\mathrm{F}}$, with $|k\ensuremath{-}{k}_{\mathrm{F}}|$ setting a nonvanishing energy scale, the details of $V(q)$ start to matter. We provide strong evidence that any curvature of the two-particle interaction at small transferred momentum $q$ destroys power-law scaling of the momentum-resolved spectral function as a function of energy. Even for $|k\ensuremath{-}{k}_{\mathrm{F}}|$ much smaller than the momentum-space range of the interaction the spectral line shape depends on the details of $V(q)$. The significance of our results for universality in the Luttinger liquid sense, for experiments on quasi-one-dimensional metals, and for recent results on the spectral function of one-dimensional correlated systems taking effects of the curvature of the single-particle dispersion into account (``nonlinear LL phenomenology'') is discussed.