Geometric constraints on phase coexistence in vanadium dioxide single crystals.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Stripe phases are characteristic of strongly correlated quantum materials.
• The origin of these phases is linked to the interplay of atomic and mesoscopic material properties.
• Vanadium dioxide (VO2) is a key phase-changing material exhibiting such phenomena.

Purpose of the Study:

• To investigate the nature of stripe phases in low-aspect-ratio, single-crystal VO2 microbeams.
• To understand the spatial organization and evolution of metallic and insulating domains.
• To explore the influence of ferroelastic domains on the observed phase patterns.

Main Methods:

• Utilized infrared nano-imaging techniques.
• Employed single-crystal VO2 microbeams with low aspect ratios.
• Decorated microbeams with resonant plasmonic nanoantennas (gold nanorods) to probe near-field responses.

Main Results:

• Observed a novel herringbone pattern of coexisting metallic and insulating domains.
• This pattern was found to be intercepted and modified by ferroelastic domains.
• Metallic domains were observed to nucleate below the crystal surface and grow upwards with increasing temperature, as indicated by plasmonic responses.

Conclusions:

• The domain structure in low-aspect-ratio VO2 differs significantly from high-aspect-ratio crystals, challenging previous models of alternating stripe phases.
• Ferroelasticity plays a crucial role in shaping the observed domain patterns.
• The findings suggest a subsurface nucleation mechanism for metallic domains in VO2.