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arXiv · 2608.14362

Tuning crystal-fields by He-irradiation and orbital Widom line in SrVO$_3$ films

Matthias Pickem·Karsten Held·Jan M. Tomczak
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Abstract

Helium-ion irradiation of epitaxial SrVO$_3$/SrTiO$_3$ films causes a metal-insulator transition, so far attributed to a Mott localization driven by a reduced kinetic energy. Using density-functional theory plus dynamical mean-field theory, we show that the driving mechanism is instead the crystal-field splitting generated by the irradiation-induced tetragonal expansion, not the interaction-to-bandwidth ratio. The resulting $c$-axis vs. temperature phase diagram mirrors that of the one-band Hubbard model, but its critical end-point spawns an orbital Widom line, rooted in an anomalous compressibility of orbital, rather than charge occupation. At an effectively quarter filling, superexchange-like processes favor orbital over magnetic long-range order. Our results semi-quantitatively reproduce the fluence-dependent spectral gaps and transition thresholds reported experimentally, establishing ion implantation as a route to chemically expand correlated materials.

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Matthias Pickem, Karsten Held, Jan M. Tomczak. 2026-08-14. Tuning crystal-fields by He-irradiation and orbital Widom line in SrVO$_3$ films. https://arxiv.org/abs/2608.14362

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