Browsing by Author "Li, Lisi"

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    Exchange field enhanced upper critical field of the superconductivity in compressed antiferromagnetic EuTe2
    (Springer Nature, 2023) Sun, Hualei; Qiu, Liang; Han, Yifeng; Zhang, Yunwei; Wang, Weiliang; Huang, Chaoxin; Liu, Naitian; Huo, Mengwu; Li, Lisi; Liu, Hui; Liu, Zengjia; Cheng, Peng; Zhang, Hongxia; Wang, Hongliang; Hao, Lijie; Li, Man-Rong; Yao, Dao-Xin; Hou, Yusheng; Dai, Pengcheng; Wang, Meng; Rice Center for Quantum Materials
    Understanding the interplay between superconductivity and magnetism has been a longstanding challenge in condensed matter physics. Here we report high pressure studies on the C-type antiferromagnetic semiconductor EuTe2 up to 36.0 GPa. A structural transition from the I4/mcm to the C2/m space group is identified at ~16 GPa. Superconductivity is observed above ~5 GPa in both structures. In the low-pressure phase, magnetoresistance measurements reveal strong couplings between the local moments of Eu2+ and the conduction electrons of Te 5p orbits. The upper critical field of superconductivity is well above the Pauli limit. While EuTe2 becomes nonmagnetic in the high-pressure phase and the upper critical field drops below the Pauli limit. Our results demonstrate that the high upper critical field of EuTe2 in the low-pressure phase is due to the exchange field compensation effect of Eu2+ and the superconductivity in both structures may arise in the framework of the Bardeen-Cooper-Schrieffer theory.
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    Single-crystal growth and superconductivity in RbNi2Se2
    (American Physical Society, 2022) Liu, Hui; Hu, Xunwu; Guo, Hanjie; Teng, Xiao-Kun; Bu, Huanpeng; Luo, Zhihui; Li, Lisi; Liu, Zengjia; Huo, Mengwu; Liang, Feixiang; Sun, Hualei; Shen, Bing; Dai, Pengcheng; Birgeneau, Robert J.; Yao, Dao-Xin; Yi, Ming; Wang, Meng
    We report the synthesis and characterization of RbNi2Se2, an analog of the iron chalcogenide superconductor RbxFe2Se2, via transport, angle-resolved photoemission spectroscopy, and density functional theory calculations. A superconducting transition at Tc=1.20 K is identified. In the normal state, RbNi2Se2 shows paramagnetic and Fermi-liquid behaviors. A large Sommerfeld coefficient yields an effective electron mass of m∗≈6me. In the superconducting state, zero-field electronic specific-heat data Ces can be described by a two-gap BCS model, indicating that RbNi2Se2 is a possible multigap superconductor. Our density functional theory calculations and angle-resolved photoemission spectroscopy measurements demonstrate that RbNi2Se2 exhibits relatively weak correlations and multiband characteristics, consistent with the multigap superconductivity.