Ultracold few fermionic atoms in needle-shaped double wells: spin chains and resonating spin clusters from microscopic Hamiltonians emulated via antiferromagnetic Heisenberg and t-J models

TL;DR

This paper demonstrates how ultracold fermionic atoms in double well traps form antiferromagnetic and quantum magnetic structures, modeled by Heisenberg and t-J Hamiltonians, revealing potential for quantum computing applications.

Contribution

It introduces exact diagonalization studies of few ultracold fermions in double wells, connecting microscopic Hamiltonians to effective spin models and exploring their complex magnetic states.

Findings

Formation of antiferromagnetic ground states in few-atom systems.

Emergence of coupled resonating 2D Heisenberg clusters.

Potential for three-atom double wells as quantum computing qubits.

Abstract

Advances with trapped ultracold atoms intensified interest in simulating complex physical phenomena, including quantum magnetism and transitions from itinerant to non-itinerant behavior. Here we show formation of antiferromagnetic ground states of few ultracold fermionic atoms in single and double well (DW) traps, through microscopic Hamiltonian exact diagonalization for two DW arrangements: (i) two linearly oriented one-dimensional, 1D, wells, and (ii) two coupled parallel wells, forming a trap of two-dimensional, 2D, nature. The spectra and spin-resolved conditional probabilities reveal for both cases, under strong repulsion, atomic spatial localization at extemporaneously created sites, forming quantum molecular magnetic structures with non-itinerant character. These findings usher future theoretical and experimental explorations into the highly-correlated behavior of ultracold strongly-repelling fermionic atoms in higher dimensions, beyond the fermionization physics that is strictly applicable only in the 1D case. The results for four atoms are well described with finite Heisenberg spin-chain and cluster models. The numerical simulations of three fermionic atoms in symmetric double wells reveal the emergent appearance of coupled resonating 2D Heisenberg clusters, whose emulation requires the use of a t-J-like model, akin to that used in investigations of high T$_c$ superconductivity. The highly entangled states discovered in the microscopic and model calculations of controllably detuned, asymmetric, double wells suggest three-cold-atom DW quantum computing qubits.