Decoupling of Lattice and Orbital Degrees of Freedom in an Iron-Pnictide Superconductor

Abstract

The interplay of structural and electronic phases in iron-based superconductors is a central theme in the search for the superconducting pairing mechanism. While electronic nematicity, defined as the breaking of four-fold symmetry triggered by electronic degrees of freedom, is competing with superconductivity, the effect of purely structural orthorhombic order is unexplored. Here, using x-ray diffraction (XRD), we reveal a new structural orthorhombic phase with an exceptionally high onset temperature ($T_{\mathrm{ort}}\sim 250$ K), which coexists with superconductivity ($T_{\mathrm{c}}=25$ K), in an electron-doped iron-pnictide superconductor far from the underdoped region. Furthermore, our angle-resolved photoemission spectroscopy (ARPES) measurements demonstrate the absence of electronic nematic order as the driving mechanism, in contrast to other underdoped iron pnictides where nematicity is commonly found. Our results establish a new, high temperature phase in the phase diagram of iron-pnictide superconductors and impose strong constraints for the modeling of their superconducting pairing mechanism.

arXiv commentSI available upon request

References in corpus (26)

• Superconductivity in Iron Compounds
• Nematic order in iron superconductors - who is in the driver's seat?
• Evidence for an electron nematic phase transition in underdoped iron pnictide superconductors
• Magnetic order in BaFe2As2, the parent compound of the FeAs based superconductors in a new structural family
• Nematic Fermi Fluids in Condensed Matter Physics
• Divergent nematic susceptibility in an iron arsenide superconductor
• Symmetry breaking orbital anisotropy on detwinned Ba(Fe1-xCox)2As2 above the spin density wave transition
• Anomalous suppression of the orthorhombic distortion in superconducting Ba[Fe(1-x)Cox]2As2
• Emergence of the nematic electronic state in FeSe
• Ubiquitous signatures of nematic quantum criticality in optimally doped Fe-based superconductors
• Enhancement of superconductivity near a nematic quantum critical point
• A precise method for visualizing dispersive features in image plots
• Uniaxial strain detwinning of CaFe2As2 and BaFe2As2: optical and transport study
• Role of the orbital degree of freedom in iron-based superconductors
• A facility for the analysis of the electronic structures of solids and their surfaces by synchrotron radiation photoelectron spectroscopy
• Symmetry breaking via orbital-dependent reconstruction of electronic structure in uniaxially strained NaFeAs
• Strong cooperative coupling of pressure-induced magnetic order and nematicity in FeSe
• Evidence for unidirectional nematic bond ordering in FeSe
• Electronic reconstruction through the structural and magnetic transitions in detwinned NaFeAs
• The Nematic Energy Scale and the Missing Electron Pocket in FeSe
• Electronic anisotropies revealed by detwinned ARPES measurements of FeSe
• Local orthorhombicity in the magnetic $C_4$ phase of the hole-doped iron-arsenide superconductor Sr${}_{1-x}$Na${}_x$Fe${}_2$As${}_2$
• Local orthorhombic lattice distortions in the paramagnetic tetragonal phase of superconducting NaFe${}_{1-x}$Ni${}_x$As
• Orbital transmutation and the electronic spectrum of FeSe in the nematic phase
• L4Fe2As2Te1-xO4-yFy (L = Pr, Sm, Gd): a layered oxypnictide superconductor with Tc up to 45 K
• Magnetotransport studies of Superconducting Pr${}_4$Fe${}_2$As${}_2$Te${}_{1-x}$O${}_4$