Fractionalization from Kinetic Frustration in Doped Two-Dimensional SU(4) Quantum Magnets

TL;DR

This paper uncovers a new fractionalization mechanism in doped SU(4) quantum magnets, where holes split into spinons and holons to relieve kinetic frustration, supported by analytical and numerical methods.

Contribution

It identifies a novel fractionalization process driven by kinetic frustration in doped SU(4) models on frustrated lattices, supported by large-N analysis and numerical simulations.

Findings

Holes fractionalize into fermionic spinons and bosonic holons at quarter filling.

Kinetic frustration is relieved by fractionalization, leading to a spinon Fermi surface.

Electron doping induces ferromagnetism similar to Nagaoka's theorem.

Abstract

Separating electrons into emergent fractional quasiparticles is a hallmark of exotic quantum phases of matter with strong interactions. Understanding under which circumstances fractionalized excitations appear is a major conceptual challenge and can help realize long sought-after states, such as quantum spin liquids. Here, we identify a distinct mechanism for fractionalization. Starting from the plaquette-ordered ground state of an SU(4) symmetric t-J model at quarter filling on frustrated triangular lattices, we reveal a compelling interplay between order and fractionalization as a function of doping. For hole doping, we find that the kinetic frustration can be relieved by fractionalizing the holes into fermionic spinons and bosonic holons: the holons minimize their kinetic energy when the spinons form a spinon Fermi surface. We support this mechanism analytically in the large-N limit as well as numerically by simulating the SU(4) case with matrix product states on cylinder geometries and with variational Monte Carlo methods on system sizes up to 40x40. Conversely, electron doping drives the system into a ferromagnetic phase, akin to Nagaoka's theorem. We discuss possible experimental realizations in moir\'e heterostructures as well as ultracold atoms, and propose dynamical probes to search for key characteristics of the fractionalized quasiparticles.