Nanoscale spectroscopic imaging of phase separation in a correlated material by resonant X-ray holography

TL;DR

This paper demonstrates that resonant soft-X-ray holography can image nanoscale phase separation in correlated materials like VO2, revealing domain nucleation, growth, and spectral properties with high spatial resolution.

Contribution

It introduces the use of resonant soft-X-ray holography for nanoscale imaging of phase separation, enabling detailed real-space visualization of domain dynamics in correlated materials.

Findings

Nanoscale metallic domains nucleate and grow within insulating VO2.

Spectral analysis yields differential soft X-ray absorption spectra at 50 nm resolution.

Potential to capture ultrafast dynamics near phase transition temperatures.

Abstract

Nanoscale phase coexistence and inhomogeneity are ubiquitous in correlated electron materials, existing in doped Mott insulators, manganites, and high-temperature superconductors. The small length scales and lack of contrast mechanisms make it extremely challenging to measure real-space images of the phase coexistence with high resolution. Yet, images aid our understanding of how phase coexistence and domain boundaries dictate the exotic material properties. Here we show that resonant soft-X-ray holography, previously employed to image magnetic domains, can be used to image phase separation on the nanoscale. We observe nucleation and growth of nanometre-sized metallic domains out of the insulating phase of the prototypical correlated material VO2, using linearly polarized coherent synchrotron radiation. By spectrally resolving the holograms, we extract differential soft X-ray absorption spectra with 50 nm spatial resolution. Furthermore, when combined with ultra-bright and ultra-short X-ray sources, X-ray holography could capture both nanoscale spatial variations and temporal fluctuations that occur close to the transition temperatures or are induced by femtosecond light pulses that cannot be observed with alternative imaging methods.