Pressure-induced nontrivial Z2 band topology and superconductivity in the transition metal chalcogenide Ta2Ni3Te5

The unique electronic and crystal structures driven by external pressure in transition metal chalcogenides (TMCs) can host emergent quantum states. Here we report pressure-induced metallization, nontrivial ${Z}_{2}$ band topology, and superconductivity in TMC ${\mathrm{Ta}}_{2}{\mathrm{Ni}}_{3}{\mathrm{Te}}_{5}$. Our electrical transport measurements show that the metallization emerges at 3.3 GPa, followed by appearance of the superconductivity at ${P}_{\mathrm{c}}=21.3\phantom{\rule{0.28em}{0ex}}\mathrm{GPa}$ with ${T}_{\mathrm{c}}\ensuremath{\sim}0.4\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. Room-temperature synchrotron x-ray-diffraction experiments demonstrate the stability of the pristine orthorhombic structure upon compression. Our first-principles calculations further reveal a topological phase transition (from ${Z}_{2}=0$ to ${Z}_{2}=1$), which occurs after ${\mathrm{Ta}}_{2}{\mathrm{Ni}}_{3}{\mathrm{Te}}_{5}$ is turned into an electron-hole compensated semimetal by pressure. The pressure-induced superconductivity at ${P}_{\mathrm{c}}$ could be attributed to the abruptly enhanced density of states at the Fermi level. These findings demonstrate that ${\mathrm{Ta}}_{2}{\mathrm{Ni}}_{3}{\mathrm{Te}}_{5}$ is a new platform for realizing exotic quantum phenomena in TMCs as well as exploring the interplay between topological property and superconductivity.