Orbital quantum magnetism in spin dynamics of strongly interacting magnetic lanthanide atoms

TL;DR

This paper models the quantum magnetism of ultracold lanthanide atoms, revealing how orbital anisotropy and anisotropic interactions influence spin dynamics in optical lattices, with implications for understanding exotic magnetic phases.

Contribution

It introduces multi-channel simulations for lanthanide atoms in optical lattices, highlighting the role of orbital anisotropy in their quantum magnetism, contrasting with simpler models.

Findings

Orbital anisotropy governs erbium atom spin dynamics.

Spin-dependent contact interactions dominate chromium atom behavior.

External magnetic field and lattice geometry affect spin evolution.

Abstract

Laser cooled lanthanide atoms are ideal candidates with which to study strong and unconventional quantum magnetism with exotic phases. Here, we use state-of-the-art closed-coupling simulations to model quantum magnetism for pairs of ultracold spin-6 erbium lanthanide atoms placed in a deep optical lattice. In contrast to the widely used single-channel Hubbard model description of atoms and molecules in an optical lattice, we focus on the single-site multi-channel spin evolution due to spin-dependent contact, anisotropic van der Waals, and dipolar forces. This has allowed us to identify the leading mechanism, orbital anisotropy, that governs molecular spin dynamics among erbium atoms. The large magnetic moment and combined orbital angular momentum of the 4f-shell electrons are responsible for these strong anisotropic interactions and unconventional quantum magnetism. Multi-channel simulations of magnetic Cr atoms under similar trapping conditions show that their spin-evolution is controlled by spin-dependent contact interactions that are distinct in nature from the orbital anisotropy in Er. The role of an external magnetic field and the aspect ratio of the lattice site on spin dynamics is also investigated.