Thermal hysteresis in scattering by vanadium-dioxide spheres

TL;DR

This paper investigates the thermal hysteresis effects in the electromagnetic scattering properties of vanadium dioxide spheres across its phase transition, revealing signatures in various scattering efficiencies and quasistates.

Contribution

It provides a detailed analysis of how thermal hysteresis influences scattering efficiencies of VO2 spheres, highlighting signatures and quasistates during phase transitions.

Findings

Clear signatures of hysteresis in scattering efficiencies below 1100 nm

Identification of vacuum and null-permittivity quasistates during phase transition

No significant efficiency differences between quasistates

Abstract

Vanadium dioxide (VO2) transforms from purely monoclinic to purely tetragonal on being heated from 58 deg C to 72 deg C, the transformation being reversible but hysteretic. Electromagnetically, VO2 transforms from a dissipative dielectric to another dissipative dielectric if the free-space wavelength is less than 1100 nm, but from a dissipative dielectric to a plasmonic metal (or vice versa) if the free-space wavelength exceeds 1100 nm. Calculating the extinction, total scattering, absorption, radiation-pressure, back-scattering, and forward-scattering efficiencies of a VO2 sphere, we found clear signatures of thermal hysteresis in (i) the forward-scattering, back-scattering, and absorption efficiencies for free-space wavelength less than 1100 nm, and (ii) the forward-scattering, back-scattering, total scattering, and absorption efficiencies for free-space wavelength more than 1100 nm. Vacuum and null-permittivity quasistates occur between 58 deg C and 72 deg C, when tetragonal VO2 is a plasmonic metal, once each on the heating branch and once each on the cooling branch of thermal hysteresis. But none of the six efficiencies show significant differences between the two quasistates.