Fig. 3: Phenomenological model illustrates formation of commensurate CDWs with out-of-plane twin degeneracy.
From: Two-dimensional charge order stabilized in clean polytype heterostructures
a–c The CDW wave-vector direction θ defines an order parameter with degenerate commensurate twins when cooled from IC-CDW phase. Simulated far-field diffraction patterns for a α-C, b IC, and c β-C. The free energy (F) landscape (Inset-left) governs the mean θ and the real-space distribution (Inset-right). d Histogram of θ shows zero-centered, wide distribution at high temperature. At low temperature, the distribution is narrow and centered at ±13.9° for either twin. e Map of local orientation of wave vector (θ) at IC phase. Each hexagonal cell represents θ at each Ta site. f At high temperature θ is mean centered and disordered, however, g at low-temperature each 2D layer converges into either α or β randomly when layers are decoupled. Simulated far-field diffraction patterns of multi-layer system in high temperature (Inset—f) and low temperature (Inset—g) resembles experimentally observed SAEDs.
