Colossal Cryogenic Electro-Optic Response Through Metastability in Strained BaTiO₃ Thin Films.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Quantum Technologies

Background:

• Barium titanate (BaTiO3) thin films are crucial for quantum computing applications.
• Their electro-optic performance significantly degrades at cryogenic temperatures due to phase transitions.
• Maintaining high electro-optic properties at low temperatures is a critical challenge.

Purpose of the Study:

• To design and demonstrate a barium titanate thin film with enhanced electro-optic properties at cryogenic temperatures.
• To engineer phase transformations to stabilize a low-symmetry phase with superior optical response.
• To overcome the performance degradation of conventional electro-optic materials at low temperatures.

Main Methods:

• Utilized thermodynamic theory of optical properties to design material.
• Engineered energetic competition between ferroelectric phases.
• Fabricated strain-tuned BaTiO3 thin films and characterized their electro-optic response at cryogenic temperatures (5 K).

Main Results:

• Demonstrated a novel low-symmetry monoclinic phase in strain-tuned BaTiO3 thin films.
• Achieved a record linear electro-optic coefficient of 2516 ± 100 pm V⁻¹ at 5 K.
• Observed a 100x increase in electro-optic coefficient upon cooling, contrasting conventional material behavior.
• Detected significant higher-order electro-optic responses at low temperatures.

Conclusions:

• A new framework for designing electro-optic materials with enhanced properties at cryogenic temperatures has been established.
• Stabilizing tunable metastable phases through strain engineering is a viable strategy for property enhancement.
• The developed BaTiO3 thin films show exceptional promise for quantum computing and other low-temperature optical applications.