Critical Slowing Down of Quadrupole and Hexadecapole Orderings in Iron Pnictide Superconductor

Abstract

Ultrasonic measurements have been carried out to investigate the critical dynamics of structural and superconducting transitions due to degenerate orbital bands in iron pnictide compounds with the formula Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$. The attenuation coefficient ${\alpha }_{\mathrm{L}[110]}$ of the longitudinal ultrasonic wave for $(C_{11}+C_{12}+2C_{66})/2$ for $x=0.036$ reveals the critical slowing down of the relaxation time around the structural transition at $T_{\mathrm{s}}=65$ K, which is caused by ferro-type ordering of the quadrupole $O_{x^{\prime 2}-y^{\prime 2}}$ coupled to the strain ${\epsilon }_{xy}$. The attenuation coefficient ${\alpha }_{66}$ of the transverse ultrasonic wave for $C_{66}$ for $x=0.071$ also exhibits the critical slowing down around the superconducting transition at $T_{\mathrm{SC}}=23$ K, which is caused by ferro-type ordering of the hexadecapole $H_z^{\alpha }({\mathbf{r}}_i,{\mathbf{r}}_j)=O_{x^{\prime }{y}^{\prime }}\left({\mathbf{r}}_i\right)O_{x^{\prime 2}-y^{\prime 2}}\left({\mathbf{r}}_j\right)+O_{x^{\prime 2}-y^{\prime 2}}\left({\mathbf{r}}_i\right)O_{x^{\prime }{y}^{\prime }}\left({\mathbf{r}}_j\right)$ of the bound two-electron state coupled to the rotation ${\omega }_{xy}$. It is proposed that the hexadecapole ordering associated with the superconductivity brings about spontaneous rotation of the macroscopic superconducting state with respect to the host tetragonal lattice.

References in corpus (24)

• Superconductivity at 38 K in the iron arsenide (Ba1-xKx)Fe2As2
• Unconventional pairing originating from disconnected Fermi surfaces in superconducting LaFeAsO${}_{1-x}$F${}_x$}
• Superconductivity at 22 K in Co-doped BaFe2As2 Crystals
• Spin density wave anomaly at 140 K in the ternary iron arsenide BaFe2As2
• Observation of Fermi-surface-dependent nodeless superconducting gaps in Ba0.6K0.4Fe2As2
• Magnetic order in BaFe2As2, the parent compound of the FeAs based superconductors in a new structural family
• LiFeAs: An Intrinsic FeAs-based Superconductor with Tc = 18K
• Effects of Co substitution on thermodynamic and transport properties and anisotropic $H_{c2}$ in Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$ single crystals
• Determination of the phase diagram of the electron doped superconductor Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$
• Nematic and meta-nematic transitions in the iron pnictides
• Anisotropic thermodynamic and transport properties of single crystalline (Ba${}_{1-x}$K${}_x$)Fe${}_2$As${}_2$ (x = 0 and 0.45)
• The challenge of unravelling magnetic properties in LaFeAsO
• Spin-orbital frustrations and anomalous metallic state in iron-pnictide superconductors
• Reconstruction of Band Structure Induced by Electronic Nematicity in an FeSe Superconductor
• Microwave Penetration Depth and Quasiparticle Conductivity in PrFeAsO_1-y Single Crystals : Evidence for a Full-Gap Superconductor
• Lifting of xz/yz orbital degeneracy at the structural transition in detwinned FeSe
• Self-Consistent Vertex Correction Analysis for Iron-Based Superconductors: Mechanism of Coulomb-Interaction-Driven Orbital Fluctuations
• A neutron scattering study of the interplay between structure and magnetism in Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$
• Electronic Structure of Prototype AFe_2As_2 and ReOFeAs High-Temperature Superconductors: a Comparison
• Suppression of Magnetic Order by Pressure in BaFe2As2
• Nodes in the Gap Function of LaFePO, the Gap Function of the Fe(Se,Te) Systems, and the STM Signature of the s${}_{\pm }$ Pairing
• Pressure versus concentration tuning of the superconductivity in Ba(Fe(1-x)Cox)2As2
• Full Gap Superconductivity in Ba${}_{0.6}$K${}_{0.4}$Fe${}_2$As${}_2$ Probed by Muon Spin Rotation
• A High-Tc Mechanism of Iron Pnictide Superconductivity due to Cooperation of Ferro-orbital and Antiferromagnetic Fluctuations

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