2004/10/20 by Ran Jin, R. Jin, B. C. Sales +8
Materials Science · Physics and Astronomy · #Advanced Thermoelectric Materials and Devices #FOS: Physical sciences #Physics of Superconductivity and Magnetism #Superconductivity (cond-mat.supr-con) #Thermal Expansion and Ionic Conductivity #cond-mat.supr-con
paper · pdf · doi:10.48550/arxiv.cond-mat/0410517
4 page, 3 figures, 1 table
arxiv created 2004/10/20 · openalex publication_date 2004/10/20 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We report specific heat measurements down to 0.4 K on the layered oxide NaxCoO2⋅\ityH2O/D2O with 0 ≤ \itx ≤ 0.74 and \ity = 0 and 1.4. For the nonhydrated system (\ity = 0), the electronic specific heat coefficient γN and the Debye temperature ΘD vary nonmonotonically with \itx, both displaying minima when \itx is close to 0.5. This indicates a systematic change of the electronic and vibrational structures with Na content. For both hydrated and deuterated systems (\itx = 0.35 and \ity = 1.4), the specific heat reveals a sharp peak with ΔCp ∼ 45.5 mJ/mol-K at Tcmid ∼ 4.7 K and an anomaly at Tx ∼ 0.8 K. While the origin of the later is unknown, the former corresponds to the superconducting transition. Interestingly, the electronic specific heat, after subtracting lattice and Schottky contributions, exhibits roughly T2 behavior between 0.2Tc and Tc. This can be explained by assuming an unconventional superconducting symmetry with line nodes. The results obtained under applied magnetic field further support this scenario.