Engineering Carrier Effective Masses in Ultrathin Quantum Wells of IrO_{2}

Jason K Kawasaki; Choong H Kim; Jocienne N Nelson; Sophie Crisp; Christian J Zollner; Eric Biegenwald; John T Heron; Craig J Fennie; Darrell G Schlom; Kyle M Shen

doi:10.1103/PhysRevLett.121.176802

Engineering Carrier Effective Masses in Ultrathin Quantum Wells of IrO_{2}

Phys Rev Lett. 2018 Oct 26;121(17):176802. doi: 10.1103/PhysRevLett.121.176802.

Authors

Jason K Kawasaki^{1

2

3

4}, Choong H Kim^{5

6}, Jocienne N Nelson², Sophie Crisp², Christian J Zollner⁷, Eric Biegenwald³, John T Heron³, Craig J Fennie⁷, Darrell G Schlom^{1

3}, Kyle M Shen^{1

2}

Affiliations

¹ Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, New York 14853, USA.
² Laboratory for Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA.
³ Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA.
⁴ Department of Materials Science and Engineering, University of Wisconsin, Madison, Wisconsin 53706, USA.
⁵ Center for Correlated Electron Systems, Institute for Basic Science, Seoul, Korea.
⁶ Department of Physics and Astronomy, Seoul National University, Seoul, Korea.
⁷ Department of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.

PMID: 30411938
DOI: 10.1103/PhysRevLett.121.176802

Abstract

The carrier effective mass plays a crucial role in modern electronic, optical, and catalytic devices and is fundamentally related to key properties of solids such as the mobility and density of states. Here we demonstrate a method to deterministically engineer the effective mass using spatial confinement in metallic quantum wells of the transition metal oxide IrO_{2}. Using a combination of in situ angle-resolved photoemission spectroscopy measurements in conjunction with precise synthesis by oxide molecular-beam epitaxy, we show that the low-energy electronic subbands in ultrathin films of rutile IrO_{2} have their effective masses enhanced by up to a factor of 6 with respect to the bulk. The origin of this strikingly large mass enhancement is the confinement-induced quantization of the highly nonparabolic, three-dimensional electronic structure of IrO_{2} in the ultrathin limit. This mechanism lies in contrast to that observed in other transition metal oxides, in which mass enhancement tends to result from complex electron-electron interactions and is difficult to control. Our results demonstrate a general route towards the deterministic enhancement and engineering of carrier effective masses in spatially confined systems, based on an understanding of the three-dimensional bulk electronic structure.