STM Study of the Charge Density Wave Gap in 2H-NbSe sub 2
20 March 1989
The charge density wave gap is observed in NbSe sub 2 using a low temperature STM. The value of the gap is about 34 meV yielding a 2delta/kT sub c of 25 suggesting very strong coupling. The temperature dependence and shape of the gap is quite different from the standard BCS form. The gap is even visible above the charge density wave transition. This may be in qualitative agreement with strong coupling theories.