Creation and control of a two-dimensional electron liquid at the bare SrTiO3 surface

TL;DR

This study demonstrates the formation and UV-controlled manipulation of a two-dimensional electron liquid on bare SrTiO3 surfaces, revealing complex many-body interactions and potential for oxide electronic devices.

Contribution

It shows that a 2DEG can be created and controlled on bare SrTiO3, expanding understanding of oxide interfaces without complex heterostructures.

Findings

2DEG with high electron density on SrTiO3 surface

UV light exposure modulates 2DEG density

Evidence of strong many-body interactions in the 2DEG

Abstract

Many-body interactions in transition-metal oxides give rise to a wide range of functional properties, such as high-temperature superconductivity, colossal magnetoresistance, or multiferroicity. The seminal recent discovery of a two-dimensional electron gas (2DEG) at the interface of the insulating oxides LaAlO3 and SrTiO3 represents an important milestone towards exploiting such properties in all-oxide devices. This conducting interface shows a number of appealing properties, including a high electron mobility, superconductivity, and large magnetoresistance and can be patterned on the few-nanometer length scale. However, the microscopic origin of the interface 2DEG is poorly understood. Here, we show that a similar 2DEG, with an electron density as large as 8x10^13 cm^-2, can be formed at the bare SrTiO3 surface. Furthermore, we find that the 2DEG density can be controlled through exposure of the surface to intense ultraviolet (UV) light. Subsequent angle-resolved photoemission spectroscopy (ARPES) measurements reveal an unusual coexistence of a light quasiparticle mass and signatures of strong many-body interactions.