Spin-Orbit Semimetal SrIrO_{3} in the Two-Dimensional Limit

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid State Physics

Background:

• Strontium iridate (SrIrO3) is a correlated oxide material exhibiting complex electronic behaviors.
• Understanding thickness-dependent properties is crucial for tuning material functionalities.

Purpose of the Study:

• To investigate the electronic properties of ultrathin SrIrO3 films.
• To identify the critical thickness for electronic phase transitions.
• To elucidate the role of spin fluctuations and magnetic order in these transitions.

Main Methods:

• Variable thickness thin film growth of SrIrO3.
• Low-temperature magnetoconductance measurements.
• Scanning tunneling spectroscopy (STS).
• Density functional theory (DFT) calculations.

Main Results:

• A transition from a semimetallic to a correlated insulating state was observed below 4 unit cells of SrIrO3.
• Spin fluctuations significantly increase as the transition point is approached.
• STS measurements indicate SrIrO3 at 4 unit cells is near a band gap opening.
• DFT calculations confirm the critical thickness and the necessity of antiferromagnetic order for gap opening.

Conclusions:

• The electronic properties of ultrathin SrIrO3 are strongly thickness-dependent.
• Spin fluctuations play a critical role in the semimetal-to-insulator transition.
• Antiferromagnetic order is essential for the emergence of the insulating state in ultrathin SrIrO3.