93Nb NMR study of the charge density wave state in NbSe2

K Ghoshray, B Pahari, A Ghoshray, V V Eremenko, V A Sirenko, and B H Suits
93Nb NMR studies were carried out for a single crystal of NbSe2 at 73.328 MHz in the temperature range 9-300K to investigate the normal and charge density wave (CDW) states. Detailed analysis of the NMR line shape of the central transition using a classical incommensurate model reveals the change in the conduction electron spin dynamics from above TCDW. An increase of the Knight shift below TCDW reflects modification to the uniform part of the conduction electron density of states. As suggested theoretically, the Knight shift distribution is found to be directly proportional to the square of the amplitude of the CDW. The results further indicate an incommensurate CDW state in 2H-NbSe2. Analysis of the NMR spectra using the McMillan incommensurate model suggests a large value of the discommensuration parameter (gamma) which is almost temperature independent, in constrast to the much small value previously reported in the case of 2H-TaSe2.

Journal of Physics: Condensed Matter 21, 155701 (2009).

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