Ion intercalation tuned quantum transport, charge density waves, and superconductivity in atomically thin crystals of 2H-TaSe₂

Quantum transport in an electronic system dealing with the quantum interference of diffusive electrons is influenced strongly by spin-orbital and electron-phonon interactions. Two-dimensional (2D) crystals of transition metal chalcogenides (TMCs) were found recently to show interesting behavior in quantum transport, which can be tuned, for example, by electric field effects. However, ion intercalation has not been used to tune quantum transport involving weak localization or weak antilocalization in 2D TMCs. We carried out magneto electrical transport measurements on atomically thin crystals of 2H-TaSe₂ intercalated by Li ions controlled by ionic gating. Gate voltage and temperature tuned crossovers from weak antilocalization to weak localization were observed. Meanwhile, ion intercalation was found to suppress charge density waves and enhance superconductivity at the same time. Band structure and phonon spectrum calculations show that the electronic density of states and the number of acoustic phonons available for scattering are reduced. Our observations suggest that the ion intercalation leads to an enhancement of the electron-phonon interaction and a simultaneous reduction in spin-orbital scattering.