Quantum critical point and superconducting dome in the pressure phase diagram ofo-TaS3

Abstract

We measure the electrical resistance of $o$-TaS${}_{3}$ between 1 and 300 K under pressures up to 20 GPa. We observe a gradual decrease of the charge density wave transition temperature ${T}_{\mathrm{CDW}}$ with increasing pressure $P$ following a mean field quantum fluctuation power law ${T}_{\mathrm{CDW}}=215\phantom{\rule{0.28em}{0ex}}\mathrm{K}{[({P}_{C}\ensuremath{-}P)/{P}_{C}]}^{\ensuremath{\gamma}}$ with a quantum critical point at a pressure ${P}_{C}=11.5\phantom{\rule{0.28em}{0ex}}\mathrm{GPa}$ and $\ensuremath{\gamma}\ensuremath{\approx}0.5$. Around the quantum critical point (QCP) we observe a superconducting dome with a maximum superconducting transition temperature ${T}_{c}=3.1\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. Such dome is similar to superconducting domes around other types of order suggesting that the QCP is directly responsible for the enhancement of superconductivity through a universal mechanism still not well understood.