Surface triggered stabilization of metastable charge-ordered phase in SrTiO₃

Area of Science:

• Condensed matter physics
• Materials science
• Solid-state chemistry

Background:

• Charge ordering (CO) involves periodic electron density modulation and lattice distortion.
• CO typically occurs in systems with high d-electron occupancy.
• CO is a key phenomenon for developing novel functional materials.

Purpose of the Study:

• To realize and investigate charge ordering in electron-doped strontium titanate (SrTiO3) with low d-electron occupancy.
• To explore the stabilization mechanisms of the charge-ordered phase in SrTiO3.
• To extend the understanding of charge ordering to new material systems.

Main Methods:

• Epitaxial thin film growth of electron-doped (100) SrTiO3.
• Theoretical calculations to predict CO states.
• Atomic-scale analysis to investigate surface and bulk properties.

Main Results:

• Successfully achieved charge ordering in SrTiO3 with the lowest d-electron occupancy (d1-d0).
• Theoretical calculations confirmed a metastable CO state in bulk SrTiO3.
• Surface distortion on (100) SrTiO3 was found to promote electron-lattice coupling, stabilizing the CO phase.

Conclusions:

• Charge ordering can be stabilized in systems with low electron occupancy, challenging previous assumptions.
• Surface effects play a crucial role in stabilizing novel electronic phases like CO.
• This work provides a pathway for stabilizing CO in a broader range of 3d transition metal oxides.