Electronic phase separation at the LaAlO₃/SrTiO₃ interface.

Area of Science:

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

Background:

• Complex oxides exhibit diverse electronic and magnetic properties, including electronic phase separation (EPS).
• EPS is linked to phenomena like colossal magnetoresistance, metal-insulator transitions, and superconductivity.
• Interfaces between complex oxides, specifically LaAlO(3)/SrTiO(3), are sites for novel electronic phases, yet EPS was not previously observed.

Purpose of the Study:

• To investigate and report the presence of electronic phase separation (EPS) at the LaAlO(3)/SrTiO(3) interface.
• To characterize the nature of the separated electronic phases and their properties.
• To elucidate the underlying mechanism responsible for the observed EPS.

Main Methods:

• Fabrication and characterization of the LaAlO(3)/SrTiO(3) interface.
• Analysis of interface charge distribution and electronic/magnetic properties.
• Investigation of Ti orbital occupancy and its role in phase formation.

Main Results:

• An electronic phase separation (EPS) state was observed at the LaAlO(3)/SrTiO(3) interface.
• The interface charges separated into distinct regions: a quasi-two-dimensional electron gas, a robust ferromagnetic phase above room temperature, and a diamagnetic/paramagnetic phase below 60 K.
• The EPS arises from selective occupancy of Ti orbital sub-bands, forming 2D-nanoscopic metallic droplets.

Conclusions:

• The observation of EPS at the LaAlO(3)/SrTiO(3) interface confirms theoretical predictions.
• This finding highlights the emergence of complex electronic and magnetic phenomena at oxide interfaces.
• The Ti orbital plays a critical role in mediating these interfacial electronic and magnetic properties.