Fermi surface reconstruction in electron-doped cuprates without antiferromagnetic long-range order.
Fermi surface (FS) topology is a fundamental property of metals and superconductors. In electron-doped cuprate Nd2- Ce  CuO4 (NCCO), an unexpected FS reconstruction has been observed in optimal- and overdoped regime (x = 0.15-0.17) by quantum oscillation measurements (QOM). This is all the more puzzling because neutron scattering suggests that the antiferromagnetic (AFM) long-range order, which is believed to reconstruct the FS, vanishes before x = 0.14. To reconcile the conflict, a widely discussed external magnetic-field-induced AFM long-range order in QOM explains the FS reconstruction as an extrinsic property. Here, we report angle-resolved photoemission (ARPES) evidence of FS reconstruction in optimal- and overdoped NCCO. The observed FSs are in quantitative agreement with QOM, suggesting an intrinsic FS reconstruction without field. This reconstructed FS, despite its importance as a basis to understand electron-doped cuprates, cannot be explained under the traditional scheme. Furthermore, the energy gap of the reconstruction decreases rapidly near x = 0.17 like an order parameter, echoing the quantum critical doping in transport. The totality of the data points to a mysterious order between x = 0.14 and 0.17, whose appearance favors the FS reconstruction and disappearance defines the quantum critical doping. A recent topological proposal provides an ansatz for its origin.
['He|Junfeng|J|0000-0001-5584-9827', 'Rotundu|Costel R|CR|', 'Scheurer|Mathias S|MS|', 'He|Yu|Y|', 'Hashimoto|Makoto|M|', 'Xu|Ke-Jun|KJ|', 'Wang|Yao|Y|', 'Huang|Edwin W|EW|', 'Jia|Tao|T|', 'Chen|Sudi|S|', 'Moritz|Brian|B|0000-0002-3747-8484', 'Lu|Donghui|D|', 'Lee|Young S|YS|', 'Devereaux|Thomas P|TP|0000-0001-8072-9237', 'Shen|Zhi-Xun|ZX|']
angle-resolved photoemission high-temperature superconductors quantum critical point strongly correlated electrons topological order