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Exact first-order effect of interactions on the ground-state energy of harmonically-confined fermions

by Pierre Le Doussal, Naftali R. Smith, Nathan Argaman

Submission summary

Authors (as registered SciPost users): Naftali Smith
Submission information
Preprint Link: scipost_202311_00047v1  (pdf)
Date submitted: 2023-11-28 12:43
Submitted by: Smith, Naftali
Submitted to: SciPost Physics
Ontological classification
Academic field: Physics
Specialties:
  • Quantum Physics
  • Statistical and Soft Matter Physics
Approach: Theoretical

Abstract

We consider a system of $N$ spinless fermions, interacting with each other via a power-law interaction $\epsilon/r^n$, and trapped in an external harmonic potential $V(r) = r^2/2$, in $d=1,2,3$ dimensions. For any $0 < n < d+2$, we obtain the ground-state energy $E_N$ of the system perturbatively in $\epsilon$, $E_{N}=E_{N}^{\left(0\right)}+\epsilon E_{N}^{\left(1\right)}+O\left(\epsilon^{2}\right)$. We calculate $E_{N}^{\left(1\right)}$ exactly, assuming that $N$ is such that the ``outer shell'' is filled. For the case of a Coulomb interaction $n=1$, we extract the $N \gg 1$ behavior of $E_{N}^{\left(1\right)}$, focusing on the corrections to the exchange term with respect to the leading-order term that is predicted from the local density approximation applied to the Thomas-Fermi approximate density distribution. The leading correction contains a logarithmic divergence, and is of particular importance in the context of density functional theory. We also study the effect of the interactions on the fermions' spatial density. Finally, we find that our result for $E_{N}^{\left(1\right)}$ significantly simplifies in the case where $n$ is even.

Current status:
Awaiting resubmission

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Anonymous Report 1 on 2024-1-10 (Invited Report)

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