Observation of a Charge-Density Wave in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>α</mml:mi></mml:math>-U at Low Temperature

Abstract

The discovery of a charge-density wave (CDW) in $\ensuremath{\alpha}$-U at \ensuremath{\sim}43 K is reported. The mode corresponds to the condensation of a longitudinal-optic phonon near $\stackrel{\ensuremath{\rightarrow}}{\mathrm{q}}=[\frac{1}{2}, 0, 0]$ in which the atoms are displaced by \ensuremath{\sim}0.006 \AA{}A from their special positions. Large precursor effects are seen in the phonon spectra. The wave vector of the CDW is related to that of the fundamental lattice in a rather complex way, which is discussed in terms of discommensurations between the CDW (${\ensuremath{\alpha}}^{\ensuremath{'}}$ phase) and the primary $\ensuremath{\alpha}$ phase.