Strain Induced Orbital Dynamics Across the Metal Insulator Transition in Thin VO2/TiO2 (001) Films

Abstract

VO2 is a strongly correlated material, which undergoes a reversible metal insulator transition (MIT) coupled to a structural phase transition upon heating (T= 67° C). Since its discovery the nature of the insulating state has long been debated and different solid-state mechanisms have been proposed to explain its nature: Mott-Hubbard correlation, Peierls distortion or a combination of both. Moreover, still now there is a lack of consensus on the interplay between the different degrees of freedom: charge, lattice, orbital and how they contribute to the MIT. In this manuscript we will investigate across the MIT the orbital evolution induced by a tensile strain applied to thin VO2 films. The strained films allowed to study the interplay between orbital and lattice degrees of freedom and to clarify MIT properties.

Correlation induced emergent charge order in metallic vanadium dioxide

“…This means the spectral weight transfer is a direct result of lattice and correlation interplay that is strongly enhanced in the [110] growth, because neither alone can reproduce experiment. We additionally see similar effects in the [100] growth orientation where explicit lattice symmetry breaking does not occur, but spectral signatures of correlation enhancement persist [43,44]. Ultimately, the evolution of the XAS waveform represents an experimental signature that non-local correlations have broken the equivalence between the two vanadium sites in the rutile phase, and the spectral features are quantitatively reproduced by a first principles analysis.…”

“…While the resistivity switching in these new memristors is acheived by driving in a non-equilibrium thermal enviornment, disputes remain as to the origin of the switching [37]. This situation has redirected massive experimental efforts towards understanding epitaxial VO 2 thin films using TiO 2 substrates, which offer the possibility of enhancing electron correlation effects with severe strain even before the Peierls distortion [38][39][40][41][42][43][44].…”

Superconductivity in Quantum Complex Matter: the Superstripes Landscape

“…Advances on quantum mechanics of orbital physics which is today a hot topic have been obtained by Oleś group showing orbital dilution in d 4 oxides by tuning crystal field potential [96] and magnetic properties of crystalline and ferroelectric layered rare-earth-titanate by Kuznetsov et al [97]. Strain Induced orbital dynamics across the metal insulator transition in thin VO 2 films [98] provide further information on nanoscale phase separation in the correlation-driven insulator-metal transition in vanadium dioxide [99][100][101][102]. The theoretical studies on nanoscale phase separation observed in cuprates [103][104][105][106] have focused on the coexistence of a metallic phase with a spin density wave phase controlled by pressure [107] of the nucleation of magnetic micro-inhomogeneity induced by an electric field [108] the order-disorder transition in a system made of two electronic components induced by nearest-neighbor repulsion [109].…”

Wave propagation and focusing of soft X-rays by spherical bent microchannel plates

“…Nowadays synchrotron radiation (SR) sources and X-ray freeelectron lasers (XFELs) provide powerful and brilliant X-ray beams that allow the structure and dynamics of matter to be investigated from atomic to mesoscale distances (Tsuji et al, 2004). Actually, brilliant X-ray spots are becoming more and more important for studying complex and functional materials at low dimensions or complex phenomena such as straindriven metal-insulator transition strongly correlated systems (D'Elia et al 2020), structural confinement in semiconducting nanowires (Rezvani et al, 2016;Pinto et al, 2016) and electrochemical dynamics of metal oxide nanoparticles (Rezvani et al, 2018;Pasqualini et al, 2017). Hence, generating a brilliant spot size is a challenging issue, but extremely important for a large class of experiments.…”