Robust Metal-Insulator Transition Despite Surface Dead-Layer Growth in Sub-10-nm Cr-Doped V2O3 Nanocrystals

TL;DR

This study shows that Cr-doped V2O3 nanocrystals maintain their metal-insulator transition down to 5.6 nm size despite surface dead-layer growth, highlighting the resilience of MIT in nanoscale materials.

Contribution

It reveals that the MIT persists in nanocrystals despite surface dead layers, offering new understanding of size effects in Mott insulators.

Findings

MIT signatures persist down to 5.6 nm size

Surface dead layers grow with decreasing size

MIT transition remains nearly size-invariant

Abstract

We investigated the size dependence of the metal-insulator transition (MIT) in Cr-doped V2O3 nanocrystals by photoemission spectroscopy using complementary probing depths, together with magnetic susceptibility measurements. Photoemission spectra show that MIT signatures persist down to an average particle size of 5.6 nm, and magnetic susceptibility measurements exhibit a nearly size-invariant transition onset. The contrast between surface-sensitive and deeper-probing photoemission spectra reveals that the transition survives in the nanocrystal interior. At the same time, the spectra indicate a systematic suppression of coherent quasiparticle weight with decreasing size, pointing to the growth of an insulating surface dead layer. These results demonstrate that nanoscaling does not intrinsically eliminate the MIT itself, but progressively enhances the influence of surface-driven insulating behavior, thereby providing insight into the practical limits of miniaturizing Mott-based devices.