Pressure-induced Lifshitz and quantum phase transitions in electron-doped cuprate superconductors.

We report observations of a pressure-induced Lifshitz transition coupled with a quantum phase transition in the electron-doped cuprate superconductor Pr0.87LaCe0.13CuO4±δ, by combining high-pressure electrical resistance, Hall coefficient (RH), and synchrotron X-ray diffraction (XRD) measurements at low temperatures. Our low-temperature Hall coefficient (RH) measurements reveal that the RH decreases continuously and reaches zero at ~10 GPa (critical pressure of Pc1). Upon further compression beyond Pc1, RH unexpectedly changes its sign from negative to positive, signaling a reconstruction of the Fermi surface from electron-dominated to hole-dominated topology. Concurrently, the superconducting transition temperature (Tc) exhibits a monotonic suppression, vanishing completely at ~17.6 GPa (critical pressure of Pc2), where the system enters a nonsuperconducting metallic state. Our low-temperature XRD measurements unequivocally demonstrate the absence of any structural phase transition across Pc1 and Pc2. Therefore, the sign change in RH at Pc1 is associated with a Lifshitz transition, which is never found in the compressed bulk electron- or hole-doped cuprate superconductors. Moreover, the quantum phase transition observed at Pc2 contrasts sharply with known high-pressure behavior of hole-doped cuprates, uncovering a fundamental difference on how pressure tunes the ground states of electron- vs. hole-doped systems. These findings provide crucial insights into the different pressure responses on the interplay among Fermi surface topology, electronic correlations, and superconductivity between these two kinds of cuprate superconductors.