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中国物理学会期刊

三角晶格自旋液体候选材料NaYbSe2在高压下的超导转变

CSTR: 32037.14.aps.72.20230730

Pressure-induced superconductivity in triangular lattice spin liquid candidate NaYbSe2

CSTR: 32037.14.aps.72.20230730
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  • 量子自旋液体是一种由于自旋阻挫直到零温都不能形成磁有序的新奇量子态, 并且和高温超导密切相关, 因此, 能否通过压力或化学掺杂等方式在量子自旋液体材料中调控出超导态甚至高温超导是一个重要的物理问题. 二维三角晶格稀土硫属化合物NaYbCh2 (Ch = O, S, Se)在比热、核磁共振、中子散射等实验中未出现长程磁有序, 被认为可能具有量子自旋液体基态. 本文研究了NaYbCh2 (Ch = Se, S, O)在压力下的电输运行为. 对于NaYbSe2, 当压力加到26.9 GPa时出现超导转变, 表现出零电阻行为, 其超导转变温度(Tc)约为5.6 K, 并且直到45 GPa都保持基本不变, 得出了其超导转变温度对压力的相图; 对于NaYbS2, 压力使其室温电阻从10 GPa下1011 Ω量级降低到67 GPa的10 Ω量级, 然而其电阻随温度行为没有出现金属性, 也没有发生超导转变; 而对于NaYbO2, 其从常压到60 GPa高压一直保持完全绝缘态, 没有可观测的电阻.

     

    Quantum spin liquid is an exotic state without magnetic order down to zero-temperature due to spin frustration, which is closely related to high temperature superconductivity. Therefore, an important issue arises whether the quantum spin liquid can be adjusted into a superconductor, even high-Tc superconductor, by using pressure or chemical doping. Rear-earth chalcogenides NaYbCh2 (Ch = O, S, Se), consisting of planar triangular lattice, exhibit no long-range magnetic order down to the lowest measured temperatures in specific heat, nuclear magnetic resonance, and neutron scattering, and are considered as a quantum spin liquid candidate. Here we investigate the electrical transport properties of NaYbCh2 (Ch = O, S, Se) under high pressures. For NaYbSe2, zero-resistance behavior is observed at 26.9 GPa, showing that the superconductivity comes into being. The superconducting transition temperature (Tc) is around 5.6 K at 26.9 GPa and robust against pressure till 45 GPa. The phase diagram of Tc versus pressure for NaYbSe2 is constructed. For NaYbS2, the room temperature resistance decreases from the order of 1011 Ω at 10 GPa to 10 Ω at 67 GPa. However, neither superconductivity nor insulator-metal transition is observed. Additionally, the NaYbO2 keeps insulating and the resistance is too large to be detected in a pressure range of 0–60 GPa.

     

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