Abstract
Many desirable material properties may be associated with disorder exhibiting local periodicity or correlations. However, few systems allow systematic studies into the effects of intrinsic crystallographic conflict on correlated disorder. The authors use epitaxial matching to stabilize an exemplar system: the pseudo-bcc U${}_{1\ensuremath{-}x}$Mo${}_{x}$ alloy, which exhibits a significant mismatch between the basis preferred symmetry and the global lattice. Employing diffuse and inelastic x-ray scattering techniques on 300-nm epitaxial films, combined with $a\phantom{\rule{0}{0ex}}b$ $i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o$ modeling, the authors discover a new form of correlated disorder which exhibits strong disorder-phonon coupling that dramatically suppresses phonon lifetimes. These findings have implications across a broad range of materials and could be exploited to develop future functional materials.
Highlights
The periodicity imbued in a crystallographic lattice has been at the heart of condensed-matter science for over a century [1]
We report extensive diffuse x-ray scattering studies on the epitaxially stabilized alloy U1−xMox, showing that a new form of intrinsically tuneable correlated disorder arises from a mismatch between the preferred symmetry of a crystallographic basis and the lattice upon which it is arranged
With extensive diffuse x-ray scattering studies, we show that the conflict created by a mismatch in preferred symmetry between a basis and the lattice produces a new form of intrinsically tuneable correlated disorder where every atom is displaced, lowering local symmetry, while maintaining the higher average symmetry imposed by the lattice
Summary
The periodicity imbued in a crystallographic lattice has been at the heart of condensed-matter science for over a century [1]. A priori one may expect the formation of correlated disorder, which thrives on symmetry mismatch [5], and the shallow configurational landscape facilitated by a high-symmetry lattice [6] When addressing these challenges, pseudo-bcc (γ s) uranium–transition-metal alloys are exemplars due to the considerable symmetry mismatch between the bcc lattice and the orthorhombic Cmcm ground state of α-uranium [19]. With extensive diffuse x-ray scattering studies, we show that the conflict created by a mismatch in preferred symmetry between a basis and the lattice produces a new form of intrinsically tuneable correlated disorder where every atom is displaced, lowering local symmetry, while maintaining the higher average symmetry imposed by the lattice. We show how this form of disorder couples to the phonon dispersion, affecting physical properties
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