Kondo effect with tunable spin-orbit interaction in LaTiO₃/CeTiO₃/SrTiO₃ heterostructure

Area of Science:

• Condensed Matter Physics
• Materials Science
• Thin Film Technology

Background:

• Epitaxial thin films of cerium titanate (CTO) on strontium titanate (STO) substrates are investigated.
• These films exhibit insulating and diamagnetic properties.

Purpose of the Study:

• To investigate the properties of δ-doped LaTiO3/SrTiO3 thin films with CTO.
• To understand the behavior of Kondo effect and spin-orbit interaction (SOI) at low temperatures.
• To explore the influence of CTO layer thickness on SOI.

Main Methods:

• Fabrication of epitaxial CTO films on STO substrates.
• X-ray photoelectron spectroscopy (XPS) to determine Ce and Ti valence states.
• Low-temperature measurements of Kondo effect and SOI, including weak anti-localization fitting.

Main Results:

• CTO films are highly insulating and diamagnetic with Ce3+ and Ti3+ valence states.
• δ-doped CTO/LTO/STO films exhibit Kondo effect and SOI.
• SOI shows non-monotonic behavior with increasing CTO thickness, with a maximum SOI field of 1.00 T at 6 unit cells.
• This behavior is attributed to interface screening effects and Fermi level shifts between Ti 2g subbands.

Conclusions:

• Interface screening strongly influences SOI in CTO/STO heterostructures.
• The observed non-monotonic SOI behavior is linked to orbital mixing and Fermi level crossover in Ti 2g subbands.
• These findings provide insights into tuning electronic properties in oxide heterostructures.