arXiv:1801.00144
Ground-state energy of one-dimensional free Fermi gases in the thermodynamic limit
Peter Otte, Spitzer, Wolfgang
Abstract
We study the ground-state energy of one-dimensional, non-interacting fermions subject to an external potential in the thermodynamic limit. To this end, we fix some (Fermi) energy $ν>0$, confine fermions with total energy below $ν$ inside the interval $[-L,L]$ and study the shift of the ground-state energy due to the potential $V$ in the thermodynamic limit $L\to\infty$. We show that the difference $\mathcal{E}_L(ν)$ of the two ground-state energies with and without potential can be decomposed into a term of order one (leading to the Fumi-term) and a term of order $1/L$, which yields the so-called finite size energy. We compute both terms for all possible boundary conditions explicitly and express them through the scattering data of the one-particle Schrödinger operator $-Δ+V$ on $L^2(\mathbb R)$.