77Se NMR study of the charge density wave state in 2H-NbSe2 and 1T-VSe2

Abstract

77Se NMR spectra of single-crystalline 2H-NbSe2 and 1T-VSe2 have been measured in the temperature range 7-295 K. For both compounds the NMR lineshape is strongly affected by the phase transition to the charge density wave (CDW) state at T0=31 K and 110 K, respectively. The temperature dependence of the normalized CDW amplitude (order parameter of the phase transition) is obtained from the width of the Knight shift distributions below T0. For 2H-NbSe2 the type of phasing of the locally commensurate CDW state is determined from the combined analysis of the 77Se and 93Nb NMR spectra measured on the same sample.