Hidden phase in parent Fe-pnictide superconductors

Abstract

We investigate the origin of exoticity in Fe-based systems via studying the Fermiology of CaFe2As2 employing Angle Resolved Photoemission spectroscopy (ARPES). While the Fermi surfaces (FSs) at 200 K and 31 K are observed to exhibit two dimensional (2D) and three dimensional (3D) topology, respectively, the FSs at intermediate temperatures reveal emergence of the 3D topology at much lower temperature than the structural & magnetic phase transition temperature (170 K, for the sample under scrutiny). This leads to the conclusion that the evolution of FS topology is not directly driven by the structural transition. In addition, we discover the existence in ambient conditions of energy bands related to the collapsed tetragonal (cT) phase. These bands are distinctly resolved in the high-photon energy spectra exhibiting strong Fe 3d character. They gradually move to higher binding energies due to thermal compression with cooling, leading to the emergence of 3D topology in the Fermi surface. These results reveal the so-far hidden existence of a cT phase in ambient conditions, which is argued to lead to quantum fluctuations responsible for the exotic electronic properties in Fe-pnictide superconductors.

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Cited by in corpus (6)

• Dimensionality, nematicity and Superconductivity in Fe-based systems
• Emergence of well screened states in a superconducting material of the CaFe${}_2$As${}_2$ family
• Orbital-dependent electron dynamics in Fe-pnictide superconductors
• Observation of the Dirac Dispersions in Co-doped CaFe2As2
• Anomalies in the temperature evolution of the Dirac states in a topological crystalline insulator SnTe
• Unusual role of ligand states in the electronic properties of a parent Fe-based superconductor, CaFe2As2