A spin-orbit coupling-induced two-dimensional electron gas in BiAlO₃/SrTiO₃ heterostructures

Area of Science:

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

Background:

• LaAlO3/SrTiO3 heterostructures exhibit a 2D electron gas due to electronic reconstruction.
• BiAlO3 and LaAlO3 are isostructural and isoelectronic, suggesting similar phenomena in BiAlO3/SrTiO3.

Purpose of the Study:

• Investigate the potential for a quasi-2D electron gas (q-2DEG) in BiAlO3/SrTiO3 heterostructures.
• Determine the mechanism and conditions for conductivity in these heterostructures.

Main Methods:

• Density Functional Theory (DFT) based scalar relativistic calculations.
• Inclusion of spin-orbit coupling in the crystal Hamiltonian.

Main Results:

• BiAlO3/SrTiO3 heterostructures remain insulating for film thickness up to 5 unit cells without spin-orbit coupling.
• Spin-orbit coupling induces a thickness-dependent insulator-to-metal transition.
• Conductivity originates from subsurface Bi 6p states, distinct from Ti electronic reconstruction in LaAlO3/SrTiO3.

Conclusions:

• BiAlO3/SrTiO3 heterostructures can host a tunable q-2DEG.
• External electric fields can control the q-2DEG properties.
• These findings open avenues for novel solid-state applications.