Hyperspectral Coherent Diffractive Imaging Spectroscopy of Phase and Oxidization State Co-existence

Coherent diffractive imaging (CDI) has been proposed as a promising method to study light-induced transient phases in quantum materials which exhibit intrinsic nanoscale phase co-existence [1]. Identifying and characterizing material phases in the condensed phase implies going beyond imaging alone and requires full-spectrum information, particularly for phases which may not exist in equilibrium, but this capability has yet to be demonstrated with coherent imaging methods. We have extended CDI to a full spectro-microscopy technique and used it to acquire hyperspectral images of vanadium oxide thin films with nanoscale resolution [2]. Using the full spectral information we identify the co-existence of multiple oxidization states without a priori information. Heating the sample we induce the insulator-to-metal phase transition in the VO₂ fraction of the sample, imaging the phase co-existence and recovering the full complex refractive index of all states present. Our results rule out the role of any intermediate phases in the VO₂ transition, and pave the way for future time resolved studies of light induced transient phases.

[1] J. Miao et al., Science 348, pp. 530 (2015)
[2] A.S. Johnson et al., ArXiv:2008.11992