Altermagnetism across the BCS-BEC crossover
Abstract
We study a two-dimensional paired Fermi system in which altermagnetism produces a spin splitting that depends on momentum. The interaction strength is described through the two-body binding energy, so that the chemical potential and pairing gap evolve self-consistently from the weak-coupling Bardeen-Cooper-Schrieffer (BCS) regime to the strong-coupling Bose-Einstein-condensate (BEC) regime at fixed density. The stability of the uniform paired state is examined by giving the pairs a small center-of-mass momentum and following the resulting change in free energy. We show that at zero temperature, the phase stiffness follows a universal quadratic suppression, J/J0 = 1 − (α/α0)2, across the entire fully gapped crossover regime. Deviations from this relation emerge only on the BCS side upon the opening of gapless Bogoliubov pockets, which rapidly reduce the stiffness and can trigger an instability toward finite-momentum pairing. In the BEC regime, this universal quadratic correction corresponds to the altered effective mass of the tightly bound composite bosons. The model therefore provides a simple setting in which to compare altermagnetic pair breaking on the BCS and BEC sides of the crossover.
Related
- Switchable Altermagnetism in a Layered van der Waals Metal-Organic Framework Driven by Spin-Crossover
- Robust Spin Universality Across a Ballistic-to-Diffusive Transport Crossover
- Impurity-induced trimer formation across the BCS-BEC crossover
- Kelvin-Helmholtz instability in annular superfluids across the UFG-BCS crossover
- Shapiro steps of superfluid Fermi gases in a ring trap across the BCS--BEC crossover
BibTeX
@misc{tolbatov2026altermagnetism,
title = {{Altermagnetism across the BCS-BEC crossover}},
author = {Iogann Tolbatov and Luca Salasnich},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.14613},
eprint = {2609.14613},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.14613},
}
RIS
TY - UNPB
TI - Altermagnetism across the BCS-BEC crossover
AU - Iogann Tolbatov
AU - Luca Salasnich
PY - 2026
DA - 2026/09/13
PB - arXiv
DO - 10.48550/arxiv.2609.14613
UR - https://arxiv.org/abs/2609.14613
AB - We study a two-dimensional paired Fermi system in which altermagnetism produces a spin splitting that depends on momentum. The interaction strength is described through the two-body binding energy, so that the chemical potential and pairing gap evolve self-consistently from the weak-coupling Bardeen-Cooper-Schrieffer (BCS) regime to the strong-coupling Bose-Einstein-condensate (BEC) regime at fixed density. The stability of the uniform paired state is examined by giving the pairs a small center-of-mass momentum and following the resulting change in free energy. We show that at zero temperature, the phase stiffness follows a universal quadratic suppression, J/J_0 = 1 − (α/α_0)^2, across the entire fully gapped crossover regime. Deviations from this relation emerge only on the BCS side upon the opening of gapless Bogoliubov pockets, which rapidly reduce the stiffness and can trigger an instability toward finite-momentum pairing. In the BEC regime, this universal quadratic correction corresponds to the altered effective mass of the tightly bound composite bosons. The model therefore provides a simple setting in which to compare altermagnetic pair breaking on the BCS and BEC sides of the crossover.
ER -