Effect of annealing on the specific heat of Ba(Fe1-xCox)2As2

Abstract

We report on the effect of annealing on the temperature and field dependencies of the low temperature specific heat of the electron-doped Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$ for under-(x = 0.045), optimal- (x = 0.08) and over-doped (x = 0.105 and 0.14) regimes. We observed that annealing significantly improves some superconducting characteristics in Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$. It considerably increases $T_c$, decreases ${\gamma }_0$ in the superconducting state and suppresses the Schottky-like contribution at very low temperatures. The improved sample quality allows for a better identification of the superconducting gap structure of these materials. We examine the effects of doping and annealing within a self-consistent framework for an extended s-wave pairing scenario. At optimal doping our data indicates the sample is fully gapped, while for both under and overdoped samples significant low-energy excitations possibly consistent with a nodal structure remain. The difference of sample quality offers a natural explanation for the variation in low temperature power laws observed by many techniques.

arXiv comment9 pages: added references, two figures and supplementary information; Accepted to Physical Review B (Jan 10, 2010)

References in corpus (36)

• Superconductivity at 38 K in the iron arsenide (Ba1-xKx)Fe2As2
• Unconventional sign-reversing superconductivity in LaFeAsO_(1-x)F_x
• Superconductivity at 43 K in Samarium-arsenide Oxides $SmFeAs{O}_{1-x}{F}_x$
• The Puzzle of High Temperature Superconductivity in Layered Iron Pnictides and Chalcogenides
• Superconductivity at 22 K in Co-doped BaFe2As2 Crystals
• Magnetism, superconductivity, and pairing symmetry in Fe-based superconductors
• Pnictogen height as a possible switch between high-T_c nodeless and low-T_c nodal pairings in the iron based superconductors
• 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
• Specific Heat of Mg ^{11}B_2
• Pairing Symmetry in a Two-Orbital Exchange Coupling Model of Oxypnictides
• Multiband magnetism and superconductivity in Fe-based compounds
• Scanning Tunneling Spectroscopy and Vortex Imaging in the Iron-Pnictide Superconductor BaFe${}_{1.8}$Co${}_{0.2}$As${}_2$
• Line nodes in the energy gap of high-temperature superconducting BaFe_2(As_{1-x}P_x)_2 from penetration depth and thermal conductivity measurements
• Spin susceptibility, phase diagram, and quantum criticality in the electron-doped high Tc Superconductor Ba[Fe(1-x)Co(x)]2As2
• Low temperature specific heat of the hole-doped Ba_{0.6}K_{0.4}Fe_2As_2 single crystals and electron-doped SmFeAsO_{0.9}F_{0.1} samples
• Fully Gapped Superconducting State Based on a High Normal State Quasiparticle Density of States in Ba${}_{0.6}$K${}_{0.4}$Fe${}_2$As${}_2$ Single Crystals
• Nodes in the gap structure of the iron-arsenide superconductor Ba(Fe_{1-x}Co_x)_2As_2 from c-axis heat transport measurements
• Momentum dependence and nodes of the superconducting gap in iron-pnictides
• Origin of Gap Anisotropy in Spin Fluctuation Models of the Fe-pnictides
• Lifting of nodes by disorder in extended-$s$ state superconductors: application to ferropnictides
• Calorimetric Evidence of Multiband Superconductivity in Ba(Fe0.925Co0.075)2As2
• Specific heat evidence for two-gap superconductivity in ternary-iron silicide Lu${}_2$Fe${}_3$Si${}_5$
• Band and momentum dependent electron dynamics in superconducting $\mathrm{Ba}(\mathrm{F}{\mathrm{e}}_{1-\mathrm{x}}\mathrm{C}{\mathrm{o}}_{\mathrm{x}}{)}_2\mathrm{A}{\mathrm{s}}_2$ as seen via electronic Raman scattering
• Field dependence of the zero energy density of states around vortices in an anisotropic gap superconductor
• Nanoscale superconducting gap variations, strong coupling signatures and lack of phase separation in optimally doped BaFe1.86Co0.14As2
• London penetration depth in Ba(Fe${}_{1-x}$T${}_x$)${}_2$As${}_2$ (T=Co, Ni) superconductors irradiated with heavy ions
• A doping dependent specific heat study of the superconducting gap in Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$
• Heat capacity study of BaFe${}_2$As${}_2$: effects of annealing
• Direct observation of a nodeless superconducting energy gap in the optical conductivity of iron-pnictides
• Three-dimensional nodal superconducting gap in single crystals Ba(Fe${}_{1-x}$Ni${}_x$)${}_2$As${}_2$
• Gap structure in the electron-doped Iron-Arsenide Superconductor Ba(Fe0.92Co0.08)2As2: low-temperature specific heat study
• Effect of a Zn impurity on T_c and its implication to pairing symmetry in LaFeAsO${}_{1-x}$F${}_x$
• Superfluid Density and Field-Induced Magnetism in Ba(Fe1-xCox)2As2 and Sr(Fe1-xCox)2As2 Measured with Muon Spin Relaxation
• Specific Heat vs Field in the 30 K Superconductor BaFe2(As0.7P0.3)2
• Theory of thermal conductivity in extended-$s$ state superconductors: application to ferropnictides
• Annealing effects on superconductivity in SrFe2-xNixAs2

Cited by in corpus (34)

• Superconductivity in Iron Compounds
• Gap symmetry and structure of Fe-based superconductors
• A review of two-band superconductivity: materials and effects on the thermodynamic and reversible mixed-state properties
• Massless Leggett Mode in Three-band Superconductors with Time-Reversal-Symmetry Breaking
• Strong Correlations, Strong Coupling and s-wave Superconductivity in Hole-doped BaFe2As2 Single Crystals
• Universal Lower Limit on Vortex Creep in Superconductors
• Superconducting Properties of the $s^{\pm }$-wave state: Fe-based superconductors
• Calorimetric Evidence of Strong-Coupling Multiband Superconductivity in Fe(Te0.57Se0.43) Single Crystal
• Local inhomogeneity and filamentary superconductivity in Pr-doped CaFe${}_2$As${}_2$
• Ground state, collective mode, phase soliton and vortex in multiband superconductors
• Direct measurement of the magnetic penetration depth by magnetic force microscopy
• Specific Heat Discontinuity DeltaC vs Tc in Annealed Ba(Fe1-xCox)2As2
• Competition between superconductivity and magnetic/nematic order as a source of anisotropic superconducting gap in underdoped Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$
• ${}^{75}$As NMR of Ba(Fe${}_{0.93}$Co${}_{0.07}$)${}_2$As${}_2$ in High Magnetic Field
• Evidence for line nodes in the energy gap of the overdoped Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$ from low-temperature specific heat measurements
• Improving quantum-transition temperatures in BaFe2As2-based crystals by removing local-lattice strain & electronic-structure disorder
• Power Law Like Correlation between Condensation Energy and Superconducting Transition Temperatures in Iron Pnictide/Chalcogenide Superconductors: Beyond the BCS Understanding
• Specific Heat To Hc2: Evidence for Nodes or Deep Minima in the Superconducting Gap of Under- and Overdoped Ba(Fe1-xCox)2As2
• The change of electronic state and crystal structure by post-annealing in superconducting SrFe2(As0.65P0.35)2
• Robust accidental nodes and zeroes and critical quasiparticle scaling in iron-based multiband superconductors
• The influence of spin fluctuations on the thermal conductivity in superconducting Ba(Fe_{1-x}Co_x)_2As_2
• Point contact spectroscopy in Fe-based superconductors: recent advancements and future challenges
• Temperature-composition Phase Diagrams for Ba1-xSrxFe2As2 and Ba0.5Sr0.5(Fe1-yCoy)2As2
• A polarized neutron diffraction study of the field-induced magnetization in the normal and superconducting states of Ba(Fe1-xCox)2As2 (x=0.65)
• Superconducting gap evolution in overdoped BaFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$ single crystals through nanocalorimetry
• Electronic specific heat in BaFe${}_{2-x}$Ni${}_x$As${}_2$
• Cs2NaAl1-xCrxF6: A family of compounds presenting magnetocaloric effect
• Specific Heat vs Field of LiFe1-xCuxAs
• The Origin of Condensation Energy Scaling of the Fe-based superconductors
• Superconductivity with Tc=7 K under pressure for Cu-, and Au-doped BaFe2As2
• Intrinsic superconducting properties and vortex dynamics in heavily overdoped Ba(Fe${}_{0.86}$Co${}_{0.14}$)${}_2$As${}_2$ single crystal
• A Field-directional Specific Heat Study on the Gap Structure of Overdoped Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$
• Multiband superconductivity and a deep gap minimum from the specific heat in KCa${}_2$(Fe${}_{1-x}$Ni${}_x$)${}_4$As${}_4$F${}_2$ ($x$ = 0, 0.05, 0.13)
• Gap Structure of the Overdoped Iron-Pnictide Superconductor Ba(Fe${}_{0.942}$Ni${}_{0.058}$)${}_2$As${}_2$: A Low-Temperature Specific-Heat Study