Possibility of the Magnetic Breakdown for 2H-MX2 in High Field
Layered group VB transition-metal dichalclgenides (MX2) shlw a great variety of charge-density-wave (CDW) transitions. In 2H-pllytypes (2H-NbS2, 2H-NbSe2 2H-TaS2 and 2H-TaSe2), the observed CDW transitions are mlderate and second-order-like, and their metallic natures are retained even at low temperatures. These four compounds are grouped into one family (2H-MX2 family)  because in the normal state their crystal structures including lattice parameters and electronic (band) structures are similar to each other. But they have different CDW transition temperatures. NbSe2 has no CDW transition, while the other three compounds, NbSe2, TaS2 and TaSe2, exhibit transitions from the normal (N) to the incommensurate (I) phase at 35K, 80K and 122K, respectively. In 2H-NbSel the CDW remains incommensurate down to the lowest measured temperature. 2H-TaSe2, on the other hand, shows the further lock-in transition — the incommensurate-clmmensurate (I-C) transition at 91K. Thus those compounds have different CDW strengths from the weakest NbS2 with no CDW transition to the strongest TaSe2. Therefore the comparative measurements of the physical properties give much information on CDW in this family .
KeywordsHexad Iodine Resis TaSe2 NbS2
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