The spinel-type ${\mathrm{LiV}}_2{\mathrm{O}}_4$ exhibits heavy-fermion metallic behaviors at low temperatures, but the effect of composition modulation on them is unknown. We realized the epitaxial growth of highly crystalline ${\mathrm{LiV}}_2{\mathrm{O}}_4$ films and conducted the electrochemical Li-ion intercalation (electron doping) to investigate systematic variation of transport properties in ${\mathrm{Li}}_{1+x}{\mathrm{V}}_2{\mathrm{O}}_4$. We found that adjustment of Li content during pulsed-laser deposition was important to obtain films exhibiting the heavy-fermion metallic behavior comparable to that of a bulk single crystal. At low doping regime $(x\le 0.5)$, resistivity increased with increasing electron filling. The slope of their linear $T^2$ dependence also increased in accordance of a Fermi-liquid model. At high doping regime $\left(x>0.5\right)$, a Mott transition was observed over a range of Li content where a new spinel phase and the original one coexisted. The results revealed that the electron doping induced enhancement of the electron correlation and the resultant Mott transition.

• Received 4 December 2020
• Revised 16 September 2021
• Accepted 15 November 2021

DOI:https://doi.org/10.1103/PhysRevB.104.245104