Doping Evolution of the Superconducting Gap Structure in Heavily Hole-Doped Ba1?xKxFe2As2: a Heat Transport Study

doi:10.1088/0256-307X/32/12/127403

Chin. Phys. Lett.

2015, Vol. 32

Issue (12): 127403 DOI: 10.1088/0256-307X/32/12/127403

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

Doping Evolution of the Superconducting Gap Structure in Heavily Hole-Doped Ba_1?xK_xFe₂As₂: a Heat Transport Study

HONG Xiao-Chen¹, WANG Ai-Feng², ZHANG Zhen¹, PAN Jian¹, HE Lan-Po¹, LUO Xi-Gang^2,4, CHEN Xian-Hui^2,4, LI Shi-Yan^1,3**

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

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HONG Xiao-Chen, WANG Ai-Feng, ZHANG Zhen et al 2015 Chin. Phys. Lett. 32 127403

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Abstract We perform systematic thermal conductivity measurements on heavily hole-doped Ba_1?xK_xFe₂As₂ 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.

Received: 02 November 2015 Published: 05 January 2016

PACS:	74.70.Xa	(Pnictides and chalcogenides)
	74.25.fc	(Electric and thermal conductivity)
	74.62.Dh	(Effects of crystal defects, doping and substitution)

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https://cpl.iphy.ac.cn/10.1088/0256-307X/32/12/127403 OR https://cpl.iphy.ac.cn/Y2015/V32/I12/127403

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	HONG Xiao-Chen
	WANG Ai-Feng
	ZHANG Zhen
	PAN Jian
	HE Lan-Po
	LUO Xi-Gang
	CHEN Xian-Hui
	LI Shi-Yan

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