Possible signature of broken symmetry state near the quantum critical point in P doped BaFe${}_2$As${}_2$: A Raman spectroscopy study

Abstract

We study the iron-pnictide compound BaFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$ for x $\sim$0.23, with a doping concentration near quantum criticality and enhanced nematic fluctuating state in the doping-temperature phase diagram. Transport measurements confirm the presence of a magneto-structural transition at 60K from the tetragonal to the orthorhombic phase, followed by a superconducting transition below 16K. The temperature and polarisation dependent Raman spectra reveal that there is a phonon mode at 211 cm${}^{-1}$, followed by two broad modes (BM) between 400 and 700 cm${}^{-1}$, having an energy difference of 15 meV, in the temperature range between 300K and 80K. In the non-superconducting state, the phonon mode exhibits expected polarization dependence as well as temperature evolution due to anharmonicity, strong anisotropic and thermally inert behaviour are observed for the BM. Electronic structure calculations for doped and undoped BaFe${}_2$As${}_2$ show that while Fe $d_{xz}$ and $d_{yz}$ orbitals do not split in the tetragonal phase, the splitting energy is 13.5 meV in the orthorhombic phase of the doped system, which is reasonably close to the experimentally observed value of the energy separation of the BM. We believe that reported BM possibly are the signature of electronic Raman scattering involving the crystal field levels of $d$-orbitals of Fe${}^{2+}$ due to local breaking of the C${}_4$ symmetry of the parent compound in the doped system.

References in corpus (17)

• Superconductivity at 38 K in the iron arsenide (Ba1-xKx)Fe2As2
• Spin density wave anomaly at 140 K in the ternary iron arsenide BaFe2As2
• Evidence for an electron nematic phase transition in underdoped iron pnictide superconductors
• A minimal two-band model for the superconducting Fe-pnictides
• Electronic Structure and Doping in BaFe${}_2$As${}_2$ and LiFeAs: Density Functional Calculations
• Anisotropic thermodynamic and transport properties of single crystalline (Ba${}_{1-x}$K${}_x$)Fe${}_2$As${}_2$ (x = 0 and 0.45)
• Extremely high sensitivity to uniaxial stress in pressure induced superconductivity of BaFe2As2
• Phonon anomalies in pure and underdoped R{1-x}K{x}Fe{2}As{2} (R = Ba, Sr) investigated by Raman light scattering
• Anomalous Raman scattering from phonons and electrons of superconducting FeSe${}_{0.82}$
• Emergence of Orbital Nematicity in the Tetragonal Phase of BaFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$
• Room temperature local nematicity in FeSe superconductor
• Raman spectra in iron-based quaternary CeO${}_{1-x}$F${}_x$FeAs and LaO${}_{1-x}$F${}_x$FeAs
• Intertwined spin-orbital coupled orders in the iron-based superconductors
• Electronic origin of structural transition in 122 Fe based superconductors
• Emergent phases in iron pnictides: Double-Q antiferromagnetism, charge order and enhanced nematic correlations
• Superconducting gap and nematic resonance at the quantum critical point observed by Raman scattering in $\mathrm{BaF}{\mathrm{e}}_2({\mathrm{As}}_{1-x}{\mathrm{P}}_x{)}_2$
• Magnetic and Electronic Raman Scattering at the Nodal Spin-Density-Wave Transition in BaFe2As2