What drives the MIT?: disentangling pre-transitional fluctuations in VO<sub>2</sub>
ORAL
Abstract
Metal–insulator transitions (MITs) often occur concomitantly with structural changes, making it difficult to disentangle the underlying mechanism. Two competing scenarios lie at the core of a longstanding debate: (i) the transition is driven purely by electronic interactions, or (ii) it is driven by electron–phonon coupling. These two scenarios should feature very different types of pre-transitional fluctuations as the MIT is approached: they should be predominantly electronic in nature in the second case. Using VO₂ as a case study, we investigated fluctuations within the metallic state by measuring diffuse X-ray scattering. We find that pre-formed structural dimers give rise to a strong diffuse scattering signal that follows the Thomson scattering energy dependence across the K-edge. Considering both the shape of the diffuse features and experimental noise limitations, our results rule out purely electronic fluctuations with coherence lengths <2 unit cells or >4–6 unit cells, instead favouring electron–phonon coupling as the driving mechanism of the transition.
*This work was financed by the Spanish Ministry of Science, Innovation and Universities via the 'Proyectos de Generación de conocimiento' grant PID2023-147042NA-I00 and the 'Ramón y Cajal' grant RYC-2021-030952-I. Part of the REXS measurements and sample growth were funded by the European Union's Horizon Europe research and innovation program under grant agreement No. 2031928. C.W.R. was supported by the U.S. Office of Naval Research through the NICOP Grant N62909-21-1-2028.
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Presenters
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Javier del Valle
- University of Oviedo