Tuning the Distance to a Possible Ferromagnetic Quantum Critical Point in A2Cr3As3
Tuning the Distance to a Possible Ferromagnetic Quantum Critical Point in A2Cr3As3
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调整 A(2)Cr(3)As(3) 中可能的铁磁量子临界点的距离
DOI：
10.1103/physrevlett.123.047001
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发表时间：
2019-07-24
影响因子：
8.6
通讯作者：
Zheng, Guo-qing
中科院分区：
文献类型：
--
作者：
Luo, J.;Yang, J.;Zheng, Guo-qing
虽然在反铁磁（AFM）不稳定性附近的超导性已被广泛探索，在过去的三十年左右，在化合物的铁磁（FM）自旋起伏的背景下的超导性仍然是罕见的。本文报道了A（2）Cr（3）As（3）族在常压下的As-75核四极共振测量结果。从自旋-晶格弛豫速率（1/T-1）的温度依赖性，我们发现，通过改变A的顺序A = Na，Na 0.75 K0.25，K，Rb，系统被调谐到接近一个可能的FM量子临界点（QCP）。这可能归因于Cr2-As 2-Cr2键角向90度方向减小，这增强了通过Cr2-As 2-Cr2路径的FM相互作用。当远离QCP时，Na 2Cr 3As 3的超导转变温度T-sc逐渐增加到8.0K，这与AFM的情况形成鲜明对比，T-sc通常在QCP附近显示出最大值。1/T ~（-1）在T-sc以下迅速下降，没有Hebel-Slichter峰，在特征温度T ~*（约0. 6 T-sc）以下普遍遵循T ~（-5）变化，这表明超导能隙函数中普遍存在点节点。这些结果表明，A（2）Cr（3）As（3）族可能是超流He-3的固态类似物。
Although superconductivity in the vicinity of an antiferromagnetic (AFM) instability has been extensively explored in the last three decades or so, superconductivity in compounds with a background of ferromagnetic (FM) spin fluctuations is still rare. We report As-75 nuclear quadrupole resonance measurements on the A(2)Cr(3)As(3) family, which is the first group of Cr-based superconductors at ambient pressure, with A being alkali elements. From the temperature dependence of the spin-lattice relaxation rate (1/T-1), we find that by changing A in the order of A = Na, Na0.75K0.25, K, and Rb, the system is tuned to approach a possible FM quantum critical point (QCP). This may be ascribed to the Cr2-As2-Cr2 bond angle that decreases towards 90 degrees, which enhances the FM interaction via the Cr2-As2-Cr2 path. Upon moving away from the QCP, the superconducting transition temperature T-sc increases progressively up to 8.0 K in Na2Cr3As3, which is in sharp contrast to the AFM case where T-sc usually shows a maximum around a QCP. The 1/T-1 decreases rapidly below T-sc with no Hebel-Slichter peak, and ubiquitously follows a T-5 variation below a characteristic temperature T* approximate to 0.6 T-sc, which indicates the existence of point nodes in the superconducting gap function commonly in the family. These results suggest that the A(2)Cr(3)As(3) family is a possible solid-state analog of superfluid He-3.