Robust two-gap strong coupling superconductivity associated with low-lying phonon modes in pressurized Nb5Ir3O superconductors

doi:10.1088/1674-1056/ab4047

中国物理B ›› 2019, Vol. 28 ›› Issue (10): 107401-107401.doi: 10.1088/1674-1056/ab4047

• SPECIAL TOPIC—Recent advances in thermoelectric materials and devices • 上一篇下一篇

Robust two-gap strong coupling superconductivity associated with low-lying phonon modes in pressurized Nb₅Ir₃O superconductors

Bosen Wang(王铂森), Yaoqing Zhang(张尧卿), Shuxiang Xu(徐淑香), Kento Ishigaki, Kazuyuki Matsubayashi, Jin-Guang Cheng(程金光), Hideo Hosono, Yoshiya Uwatoko

1 Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;
2 Institute for Solid State Physics, University of Tokyo, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8581, Japan;
3 Materials Research Center for Element Strategy, Tokyo Institute of Technology, Yokohama 226-8503, Japan;
4 Songshan Lake Materials Laboratory, Dongguan 523808, China

收稿日期:2019-06-16 修回日期:2019-08-15 出版日期:2019-10-05 发布日期:2019-10-05
通讯作者: Bosen Wang E-mail:bswang@iphy.ac.cn

Robust two-gap strong coupling superconductivity associated with low-lying phonon modes in pressurized Nb₅Ir₃O superconductors

Bosen Wang(王铂森)^1,2,4, Yaoqing Zhang(张尧卿)³, Shuxiang Xu(徐淑香)¹, Kento Ishigaki², Kazuyuki Matsubayashi², Jin-Guang Cheng(程金光)^1,4, Hideo Hosono³, Yoshiya Uwatoko²

1 Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;
2 Institute for Solid State Physics, University of Tokyo, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8581, Japan;
3 Materials Research Center for Element Strategy, Tokyo Institute of Technology, Yokohama 226-8503, Japan;
4 Songshan Lake Materials Laboratory, Dongguan 523808, China

Received:2019-06-16 Revised:2019-08-15 Online:2019-10-05 Published:2019-10-05
Contact: Bosen Wang E-mail:bswang@iphy.ac.cn

摘要/Abstract

摘要：

We report robust superconducting state and gap symmetry of Nb₅Ir₃O via electrical transport and specific heat measurements. The analysis of specific heat manifests that Nb₅Ir₃O is a strongly coupled superconductor with ΔC/γ_nT_c~1.91 and double s-wave superconducting gaps of 2△_L(0)/k_BT_c~6.56 and 2△_S(0)/k_BT_c~2.36 accounting for 90% and 10%, respectively. The (C_p-γ_nT)/T³ vs. T plot shows a broad peak at~23 K, indicating phonon softening and the appearance of low-lying phonon mode associated with the interstitial oxygen. This behavior explains the monotonic increase of T_c in Nb₅Ir₃O_(1-δ) by strengthening the electron-phonon coupling and enlarging the density of states at Fermi level. The Hall coefficient is temperature independent below 200 K, and changes its sign from positive to negative above 250 K, suggesting that carrier is across the hole- to electron-dominant regions and the multi-band electronic structures. On warming, the resistivity shows a gradual crossover from T²- to T³-dependence at a critical temperature T^*, and a broad peak at a temperature T_p. The reduced T_c under pressure is linearly correlated with lattice parameters c/a ratio and T_p, suggesting the important phonon contributions in Nb₅Ir₃O as a phonon-medicated superconductor. Possible physical mechanisms are proposed.

关键词: new superconductor, high-pressure effect, strongly coupled superconductor

Abstract:

Key words: new superconductor, high-pressure effect, strongly coupled superconductor

中图分类号: (Superconducting materials other than cuprates)

74.70.-b

74.62.Fj (Effects of pressure)

王铂森, 张尧卿, 徐淑香, Kento Ishigaki, Kazuyuki Matsubayashi, 程金光, Hideo Hosono, Yoshiya Uwatoko. Robust two-gap strong coupling superconductivity associated with low-lying phonon modes in pressurized Nb₅Ir₃O superconductors[J]. 中国物理B, 2019, 28(10): 107401-107401.

Bosen Wang(王铂森), Yaoqing Zhang(张尧卿), Shuxiang Xu(徐淑香), Kento Ishigaki, Kazuyuki Matsubayashi, Jin-Guang Cheng(程金光), Hideo Hosono, Yoshiya Uwatoko. Robust two-gap strong coupling superconductivity associated with low-lying phonon modes in pressurized Nb₅Ir₃O superconductors[J]. Chin. Phys. B, 2019, 28(10): 107401-107401.

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Robust two-gap strong coupling superconductivity associated with low-lying phonon modes in pressurized Nb₅Ir₃O superconductors

Robust two-gap strong coupling superconductivity associated with low-lying phonon modes in pressurized Nb₅Ir₃O superconductors

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