Doping Evolution of the Superconducting Gap Structure in Heavily Hole-Doped Ba1?xKxFe2As2: a Heat Transport Study
HONG Xiao-Chen1, WANG Ai-Feng2, ZHANG Zhen1, PAN Jian1, HE Lan-Po1, LUO Xi-Gang2,4, CHEN Xian-Hui2,4, LI Shi-Yan1,3**
1State Key Laboratory of Surface Physics, Department of Physics, and Laboratory of Advanced Materials, Fudan University, Shanghai 200433 2Hefei National Laboratory for Physical Science at Microscale and Department of Physics,University of Science and Technology of China, Hefei 230026 3Collaborative Innovation Center of Advanced Microstructures, Fudan University, Shanghai 200433 4Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093
Abstract：We perform systematic thermal conductivity measurements on heavily hole-doped Ba1?xKxFe2As2 single crystals with 0.747≤x ≤0.974. At x=0.747, the κ0/T is negligible, indicating a nodeless superconducting gap. A small residual linear term κ0/T (≈0.035 mW?K?2cm?1) appears at x=0.826, and it increases slowly up to x=0.974, followed by a substantial increase of more than 20 times to the pure KFe2As2 (x=1.0). This doping dependence of κ0/T clearly shows that the nodal gap appears near x=0.8, possibly associated with the change of Fermi surface topology. The small values of κ0/T from x=0.826 to 0.974 are consistent with the ?-shaped nodal s-wave gap recently revealed by angle-resolved photoemission spectroscopy experiments at x=0.9. Furthermore, the substantial increase of κ0/T from x=0.974 to 1.0 is inconsistent with a symmetry-imposed d-wave gap in KFe2As2, and a possible nodal gap structure in KFe2As2 is discussed.
(Effects of crystal defects, doping and substitution)
引用本文:
. [J]. 中国物理快报, 2015, 32(12): 127403-127403.
HONG Xiao-Chen, WANG Ai-Feng, ZHANG Zhen, PAN Jian, HE Lan-Po, LUO Xi-Gang, CHEN Xian-Hui, LI Shi-Yan. Doping Evolution of the Superconducting Gap Structure in Heavily Hole-Doped Ba1?xKxFe2As2: a Heat Transport Study. Chin. Phys. Lett., 2015, 32(12): 127403-127403.
2015, Vol. 32 
