Strain-dependent Metal-Insulator Tansition in VO$_{2}$ single-crystalline thin films

Vanadium dioxide (VO$_{2}$ has a near room temperature metal insulator transition (T$_{\mathrm{MIT}}$ $\sim$ 340 K) accompanied by a structural transition making the origin of this transition controversial. In this work, we have continuously changed T$_{\mathrm{MIT}}$ by as much as 60 K in VO$_{2}$ (001) single crystalline thin films by using RuO$_{2}$ buffer layers. We observe a decrease in the T$_{\mathrm{MIT}}$ as a function of decreasing c-axis length in the rutile phase which is unexpected from a one-dimensional Peierls model. By performing complementary bulk-sensitive spectroscopic measurements, namely, x-ray absorption spectroscopy (XAS) and x-ray photoelectron spectroscopy (XPS), we identify changes in orbital occupation and electron-electron correlations as a function of strain in the metallic state that explain the observed T$_{\mathrm{MIT}}$ dependence on strain.