Superconductivity induced by gate-driven hydrogen intercalation in the charge-density-wave compound 1T-TiSe2

The key role played by hydrogen (H) in the near-to-room temperature superconductivity of hydrides at megabar pressures suggests that H doping could produce similar effects in materials at ambient pressure. Here the authors show that ionic gate-driven H intercalation in the layered compound TiSe2 induces a superconducting phase with features distinct from those obtained through other doping techniques.Hydrogen (H) plays a key role in the near-to-room temperature superconductivity of hydrides at megabar pressures. This suggests that H doping could have similar effects on the electronic and phononic spectra of materials at ambient pressure as well. Here, we demonstrate the non-volatile control of the electronic ground state of titanium diselenide (1T-TiSe2) via ionic liquid gating-driven H intercalation. This protonation induces a superconducting phase, observed together with a charge-density wave through most of the phase diagram, with nearly doping-independent transition temperatures. The H-induced superconducting phase is possibly gapless-like and multi-band in nature, in contrast with those induced in TiSe2 via copper, lithium, and electrostatic doping. This unique behavior is supported by ab initio calculations showing that high concentrations of H dopants induce a full reconstruction of the bandstructure, although with little coupling between electrons and high-frequency H phonons. Our findings provide a promising approach for engineering the ground state of transition metal dichalcogenides and other layered materials via gate-controlled protonation.