Fermi surface reconstruction in electron-doped cuprates without antiferromagnetic long-range order

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Fermi surface (FS) topology is crucial for understanding metals and superconductors.
• Electron-doped cuprates like Nd_2-xCe_xCuO₄ (NCCO) exhibit puzzling FS reconstructions.
• Previous studies showed conflicting results regarding antiferromagnetism and FS reconstruction in NCCO.

Purpose of the Study:

• To investigate the Fermi surface (FS) reconstruction in optimal- and overdoped NCCO.
• To determine if the FS reconstruction is an intrinsic property or an artifact of external magnetic fields.
• To understand the relationship between FS reconstruction, mysterious order, and quantum criticality in NCCO.

Main Methods:

• Angle-resolved photoemission spectroscopy (ARPES) was used to probe the electronic structure of NCCO.
• Quantum oscillation measurements (QOM) provided complementary data on FS properties.
• Neutron scattering data was considered for magnetic ordering information.

Main Results:

• ARPES confirmed FS reconstruction in optimal- and overdoped NCCO (x = 0.15-0.17).
• The observed FS reconstruction quantitatively matched QOM results, indicating an intrinsic phenomenon.
• An energy gap associated with the reconstruction decreased rapidly near x = 0.17, behaving like an order parameter.

Conclusions:

• The FS reconstruction in NCCO is intrinsic and not caused by external magnetic fields.
• A mysterious order emerging between x = 0.14 and 0.17 drives the FS reconstruction and quantum criticality.
• This finding necessitates a re-evaluation of traditional theories for electron-doped cuprates and suggests new topological explanations.