Rocksalt CeO epitaxial thin film as a heavy-fermion system transiting from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>p</mml:mi></mml:math>-type metal to partially compensated <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>n</mml:mi></mml:math>-type metal by <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>4</mml:mn><mml:mi>f</mml:mi></mml:mrow></mml:math> delocalization
Nobuto Abe, Daichi Oka, Kenichi Kaminaga, Daisuke Shiga, Daichi Saito, Taku Yamamoto, Noriaki Kimura, Hiroshi Kumigashira, Tomoteru Fukumura
Abstract
Rocksalt CeO (001) epitaxial thin films were synthesized and their electronic properties were investigated. A simple $4{f}^{1}{5d}^{1}$ electronic configuration with $4f--5d$ hybridization in CeO was confirmed by x-ray photoemission and absorption spectroscopy. While $5d$ conduction holes governed the metallic conduction at high temperatures, a partially compensated $n$-type conduction appeared below \ensuremath{\sim}10 K with a rapid decrease in resistivity corresponding to a Fermi liquid state. The hole mobility was as high as $646\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{V}}^{--1}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{--1}$ at 2 K in contrast to the two decades lower electron mobility, reflecting the large and small dispersion of $5d$ and $4f$ bands, respectively. At 0.8 K, a resistivity minimum was observed as a manifestation of the Kondo effect, indicating partial $4f$ localization. These results represented that the significant $4f--5d$ hybridization induced a Kondo coherent state in CeO with a short Ce-Ce interionic distance unlike the other antiferromagnetic Ce chalcogenides.