Understanding the onset of negative electronic compressibility in one- and two-band 2D electron gases: Application to LaAlO${}_3$/SrTiO${}_3$

Abstract

We investigate the effects of two electronic bands at the negative electronic compressibility (NEC) in a two-dimensional electron gas (2DEG). We use a simple homogeneous model with Coulombic interactions and first-order multi-band coupling to examine the role of effective mass and relative permittivity in relation to the critical carrier density, where compressibility turns negative. We demonstrate that the population of a second band, along with the presence of inter-band coupling, can dramatically change the cross-over carrier density. Given the difficulty in determining and confirming multi-band electronic systems, this model provides a potential method for identifying multi-band electronic systems using precise bulk electronic properties measurements. To help illustrate this method, we apply our results to the observed NEC in the 2D electron gas at the interface of LaAlO${}_3$/SrTiO${}_3$ (LAO/STO) and determine that, for the known parameters of LAO/STO, the system is likely a realization of a two-band 2D electron gas. Furthermore, we provide general limits on the inter-band coupling with respect to the electronic band population.

12 Pages, 8 Figures

References in corpus (11)

• Electric Field Control of the LaAlO${}_3$/SrTiO${}_3$ Interface Ground State
• Theory of spin-orbit coupling at LaAlO3/SrTiO3 interfaces and SrTiO3 surfaces
• Electron-phonon interaction and charge carrier mass enhancement in SrTiO3
• Gate-tunable band structure of the LaAlO${}_3$-SrTiO${}_3$ interface
• Electronic compressibility of a graphene bilayer
• Optically excited multi-band conduction in LaAlO3/SrTiO3 heterostructures
• Large Negative Electronic Compressibility of LaAlO3-SrTiO3 Interfaces with Ultrathin LaAlO3 Layers
• Capacitance and compressibility of heterostructures with strong electronic correlations
• Structure-Property Relation of SrTiO3-LaAlO3 Interfaces
• Multiband superconductivity in Pb, H under pressure and CaBeSi from {\it ab-initio} calculations
• Novel mechanisms to enhance the capacitance beyond the classical limits in capacitors with free-electron-like electrodes