191 research outputs found
Origin of the tetragonal-to-orthorhombic (nematic) phase transition in FeSe: a combined thermodynamic and NMR study
The nature of the tetragonal-to-orthorhombic structural transition at
K in single crystalline FeSe is studied using shear-modulus,
heat-capacity, magnetization and NMR measurements. The transition is shown to
be accompanied by a large shear-modulus softening, which is practically
identical to that of underdoped Ba(Fe,Co)As, suggesting very similar
strength of the electron-lattice coupling. On the other hand, a
spin-fluctuation contribution to the spin-lattice relaxation rate is only
observed below . This indicates that the structural, or "nematic", phase
transition in FeSe is not driven by magnetic fluctuations
Calorimetric Evidence of Multiband Superconductivity in Ba(Fe0.925Co0.075)2As2
We report on the determination of the electronic heat capacity of a slightly
overdoped (x = 0.075) Ba(Fe1-xCox)2As2 single crystal with a Tc of 21.4 K. Our
analysis of the temperature dependence of the superconducting-state specific
heat provides strong evidence for a two-band s-wave order parameter with gap
amplitudes 2D1(0)/kBTc=1.9 and 2D2(0)/kBTc=4.4. Our result is consistent with
the recently predicted s+- order parameter [I. I. Mazin et al., Phys. Rev.
Lett. 101, 057003 (2008)].Comment: 4 pages, 3 figure
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