Enhancement of superconductivity by organic flexible substrates in NbSe₂ thin flakes

The regulation of superconductivity is of great significance in basic physics and device applications. Typically superconductivity can be tuned by chemical doping, gate voltage, and pressure. The interaction between superconductivity and substrates in low-dimensional systems is concerned in recent years, but a systematic and in-depth investigation is still lacking. Here we report a systematic study concerning the influence of substrates on the performance of superconductivity in NbSe2 thin flakes. It is found that the superconducting critical temperature Tc can be enhanced when the organic flexible substrates are adopted, as compared with that using the inorganic rigid substrates. Such an enhancement is more distinct under the applied magnetic fields. The analysis combined with Raman scattering experiments shows that the improvement of superconductivity is closely related to the softening of E2g1 phonon mode, pointing out the most possible mechanism for the effect of substrates on superconductivity. Meanwhile, the involvement of organic substrate also enhances the wave number of the charge-density-wave related soft mode.