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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NaYbCh 2(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NaYbCh 2(Ch = Se, S, O)在压力下的电输运行为. 对于NaYbSe 2, 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( T c)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NaYbS 2, 压力使其室温电阻从10 GPa下10 11Ω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NaYbO 2, 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- T csuperconductor, by using pressure or chemical doping. Rear-earth chalcogenides NaYbCh 2(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 NaYbCh 2(Ch = O, S, Se) under high pressures. For NaYbSe 2, zero-resistance behavior is observed at 26.9 GPa, showing that the superconductivity comes into being. The superconducting transition temperature ( T c) is around 5.6 K at 26.9 GPa and robust against pressure till 45 GPa. The phase diagram of T cversus pressure for NaYbSe 2is constructed. For NaYbS 2, the room temperature resistance decreases from the order of 10 11Ω at 10 GPa to 10 Ω at 67 GPa. However, neither superconductivity nor insulator-metal transition is observed. Additionally, the NaYbO 2keeps insulating and the resistance is too large to be detected in a pressure range of 0–60 GPa.
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Keywords:
- quantum spin liquid/
- high pressure/
- electrical transport
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