Ekaterina Gradova | Searcharxiv

arXiv2026

Benchmarking the fermionic quasi-1D many-body problem

We investigate the validity of effective one-dimensional models for quasi-1D fermionic systems by benchmarking a coupled-channel approach against the exact low-energy theory derived from the underlying three-dimensional problem in the weakly and strongly attractive limits. We show that reproducing the exact two-body scattering amplitude is insufficient to construct the correct effective low-energy theory of quasi-1D fermions. In the weakly attractive regime, it does not capture the emergent three-body interaction induced by transverse excitations. In the strongly attractive regime, it yields an atom-dimer scattering length with an incorrect dependence on the three-dimensional scattering length. These results demonstrate the limitations of effective one-dimensional descriptions based solely on two-body physics and highlight the need to explicitly include few-body correlations in quasi-1D systems.

cond-mat.quant-gas↗

arXiv2025

Quasi-particle residue and charge of the one-dimensional Fermi polaron

We consider a mobile impurity coupled to an ideal Fermi gas in one spatial dimension through an attractive contact interaction. We calculate the quasi-particle residue $Z$ exactly, based on Bethe Ansatz and diagrammatic Monte Carlo methods, and with varational Ansatz up to one particle-hole excitation of the Fermi sea. We find that the exact quasi-particle residue vanishes in the thermodynamic limit as a power law in the number of particles, consistent with the Luttinger-liquid paradigm and the breakdown of Fermi-liquid theory. The variational Ansatz, however, predicts a finite value of $Z$, even in the thermodynamic limit. We also study how the presence of the impurity affects the density of the spin-up sea by calculating the pair correlation function. Subtracting the homogeneous background and integrating over all distances gives the charge $Q$. This charge turns out to grow continuously from 0 at zero coupling to 1 in the strong-coupling limit. The varational Ansatz predicts $Q=0$ at all couplings. So, although the variational Ansatz has been shown to be remarkably accurate for the energy and the effective mass, it fails even qualitatively when predicting $Z$ and the pair correlation function in the thermodynamic limit.

cond-mat.quant-gas↗