Large phonon-drag enhancement induced by narrow quantum confinement at the LaAlO3/SrTiO3 interface

TL;DR

This study reveals a significant phonon-drag enhancement in the thermoelectric power at the LaAlO3/SrTiO3 interface below 50 K, driven by narrow quantum confinement that amplifies electron-phonon interactions.

Contribution

It demonstrates that quantum confinement at the LaAlO3/SrTiO3 interface dramatically increases phonon-drag thermopower, highlighting strong electron-phonon coupling effects.

Findings

Phonon-drag thermopower reaches ~mV/K below 50 K.

Enhanced phonon-drag attributed to tight carrier confinement.

Strong electron-acoustic phonon coupling at the interface.

Abstract

The thermoelectric power of the two-dimensional electron system (2DES) at the LaAlO3/SrTiO3 interface is explored below room temperature, in comparison with that of Nb-doped SrTiO3 single crystals. For the interface we find a region below T =50 K where thermopower is dominated by phonon-drag, whose amplitude is hugely amplified with respect to the corresponding bulk value, reaching values ~mV/K and above. The phonon-drag enhancement at the interface is traced back to the tight carrier confinement of the 2DES, and represents a sharp signature of strong electron-acoustic phonon coupling at the interface.