Abstract
The phason energy gap has been observed in the incommensurate and commensurate phases in the 'devil's staircase' compound (N(CH3)4)2ZnCl4. The gap was determined via the phason-induced 14N spin-lattice relaxation contribution. In the commensurate phases the gap is commensurability induced whereas in the incommensurate phase it is induced by defects. The commensurability-induced gap varies with the size of the commensurate unit cell as predicted by the theory of Levanyuk.
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