Evolution of Magnetic Double Helix and Quantum Critical near a Dome of Superconductivity in CrAs
Evolution of Magnetic Double Helix and Quantum Critical near a Dome of Superconductivity in CrAs
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CrAs 超导圆顶附近磁双螺旋的演化和量子临界性
DOI：
10.1103/physrevx.8.031017
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发表时间：
2018
影响因子：
12.5
通讯作者：
Uwatoko Y.
中科院分区：
文献类型：
--
作者：
Matsuda M.;Lin F. K.;Yu R.;Cheng J-G;Wu W.;Sun J. P.;Zhang J. H.;Sun P. J.;Matsubayashi K.;Miyake T.;Kato T.;Yan J-Q;Stone M. B.;Si Qimiao;Luo J. L.;Uwatoko Y.
在环境压力下，CrAs在TN = 265 K时发生一阶跃迁到双螺旋磁态，并伴有结构跃迁。最近在CrAs中发现的压力诱导超导性使得澄清其耦合结构/磁序的量子相变的性质变得重要。通过对单晶CrAs在静水压力(P)下的中子衍射，我们发现，在Pc ~ 10 kbar时，组合序被抑制，在此附近，块体超导性出现，最大转变温度为Tc ~ 2 K。我们进一步发现，磷掺杂在CrAs1-xPx中的耦合顺序也被完全抑制，在临界xc ~ 0.05以上，非弹性中子散射证明了持续的反铁磁相关，提供了磁性和超导性之间的可能联系。由于在Pc （xc）附近存在反铁磁波动，电阻率二次温度依赖的A系数在P (x)接近Pc （xc）时表现出显著的增强，在其周围Res(T)具有非费米液体形式。因此，CrAs1-xPx的电子比热系数在xc附近达到峰值。这些性质为量子临界性提供了明确的证据，我们将其解释为源于伴随一阶结构转变的近二阶helimagnetic量子相变。我们在CrAs中的发现突出了坏金属中量子临界性的独特特征，从而为诸如高tc铁化合物中发生的非常规超导性的物理学提供了新的见解。
At ambient pressure CrAs undergoes a first-order transition into a double-helical magnetic state at TN = 265 K, which is accompanied by a structural transition. The recent discovery of pressure-induced superconductivity in CrAs makes it important to clarify the nature of quantum phase transitions out of its coupled structural/helimagnetic order. Here we show, via neutron diffraction on the single-crystal CrAs under hydrostatic pressure (P), that the combined order is suppressed at Pc ~ 10 kbar, near which bulk superconductivity develops with a maximal transition temperature Tc ~ 2 K. We further show that the coupled order is also completely suppressed by phosphorus doping in CrAs1-xPx at a critical xc ~ 0.05, above which inelastic neutron scattering evidenced persistent antiferromagnetic correlations, providing a possible link between magnetism and superconductivity. In line with the presence of antiferromagnetic fluctuations near Pc (xc), the A coefficient of the quadratic temperature dependence of resistivity exhibits a dramatic enhancement as P (x) approaches Pc (xc), around which Res(T) has a non-Fermi-liquid form. Accordingly, the electronic specific-heat coefficient of CrAs1-xPx peaks out around xc. These properties provide clear evidences for quantum criticality, which we interpret as originating from a nearly second-order helimagnetic quantum phase transition that is concomitant with a first-order structural transition. Our findings in CrAs highlight the distinct characteristics of quantum criticality in bad metals, thereby bringing out new insights into the physics of unconventional superconductivity such as occurring in the high-Tc iron pnictides.