Spin-1 chain doped with mobile S = 1/2 fermions

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Magnetism

Background:

• Y2-xCaxBaNiO5 exhibits complex magnetic properties due to competing interactions.
• Understanding the interplay between itinerant electrons and localized spins is crucial.

Purpose of the Study:

• To model the doping effects in a two-orbital chain system relevant to Y2-xCaxBaNiO5.
• To investigate the emergence of new energy scales and excitation spectra upon doping.

Main Methods:

• Utilizing the density matrix renormalization group (DMRG) method.
• Calculating correlation functions and thermodynamic quantities.

Main Results:

• A new hierarchy of energy scales was identified in the spin sector after doping.
• Doping introduces itinerant polarons, leading to gapless spin excitations at a lower energy scale.
• These gapless excitations coexist with a gapful spin-liquid background characteristic of the S=1 chain.

Conclusions:

• The two-orbital chain model with mobile S=1/2 fermions effectively captures the physics of doped Y2-xCaxBaNiO5.
• Doping fundamentally alters the magnetic excitation spectrum, creating a multi-scale energy landscape.