Emergent spin-valley-orbital physics by spontaneous parity breaking

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid-State Physics

Background:

• Spin-orbit coupling (SOC) is crucial for exotic electronic states like topological insulators and unconventional superconductors.
• Typically, breaking spatial inversion symmetry is inherent to lattice structures, limiting external control over these properties.
• Controlling electronic states via SOC requires overcoming the challenge of inherent inversion symmetry in many materials.

Purpose of the Study:

• To theoretically investigate the generation of spin-orbital entanglement through spontaneous electronic ordering driven by electron correlations.
• To explore how local asymmetry in centrosymmetric lattices can activate hidden antisymmetric spin-orbit coupling.
• To provide a comprehensive understanding of spin-valley-orbital physics in solids.

Main Methods:

• Theoretical investigation focusing on centrosymmetric lattices with local site asymmetry (e.g., honeycomb, zigzag, diamond structures).
• Analysis of conventional staggered orders (charge, antiferromagnetic) to break inversion symmetry and activate antisymmetric SOC.
• Utilizing a minimal two-orbital model on a honeycomb lattice to scrutinize explicit forms of antisymmetric SOC for various orders.

Main Results:

• Demonstrated that electron correlations can induce spontaneous electronic ordering, breaking inversion symmetry and activating antisymmetric SOC.
• Identified explicit forms of antisymmetric SOC for charge, spin, orbital, and spin-orbital orders in honeycomb lattices.
• Showcased the utility of a complete table of these orders for understanding spin-valley-orbital physics.

Conclusions:

• Spontaneous electronic ordering driven by electron correlations offers a pathway to generate spin-orbital entanglement and control electronic states.
• Antisymmetric SOC, activated by staggered orders in lattices with local asymmetry, is key to realizing novel electronic and magnetic properties.
• The findings facilitate understanding of spin and valley splitting, generalized magnetoelectric responses, and peculiar material properties.