Speaker
Description
In pristine 2H-TaS$_2$ and 2H-NbSe$_2$, a charge-density-wave (CDW) instability is present and is generally associated with suppressed superconductivity. Hydrogen intercalation fundamentally alters this behavior: two H atoms donate two electrons per unit cell, shifting the Fermi level into an internal band gap above the valence bands. The CDW is suppressed, and the resulting systems are predominantly semiconducting, with only selected configurations remaining weakly metallic. Doping provides a route to further tune their electronic and superconducting properties: hole doping yields negligible superconductivity, whereas rigid-band electron doping can raise $T_c$ to tens of kelvin by filling sharp conduction-band states. Hydrogen intercalation therefore provides a means to engineer TMDs by suppressing the CDW and enabling subsequent control of superconductivity through doping.