Pronounced drop of $^{17}$O NMR Knight shift in superconducting state of Sr$_2$RuO$_4$.
Pronounced drop of $^{17}$O NMR Knight shift in superconducting state of Sr$_2$RuO$_4$.
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发表时间：
2019-03
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通讯作者：
A. Pustogow;Yongkang Luo;A. Chronister;Y.-S. Su;D. Sokolov;F. Jerzembeck;A. Mackenzie;C. Hicks;N. Kikugawa;S. Raghu;E. Bauer;S. Brown
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作者：
A. Pustogow;Yongkang Luo;A. Chronister;Y.-S. Su;D. Sokolov;F. Jerzembeck;A. Mackenzie;C. Hicks;N. Kikugawa;S. Raghu;E. Bauer;S. Brown
准二维强相关Sr$_2$RuO$_4$中的超导态被认为是与超流体$^3$He-$ a $类似的固体态，其奇宇称序参数也打破了时间反转对称性，并且在所有电子动量的自旋空间中矢量序参数具有相同的方向。最近发现单轴压力导致应变样品的转变温度急剧上升和最大（T_c），这激发了我们在本文中描述的$^{17}$O核磁共振（NMR）的研究。在所有应变值和温度$T<T_c$下，观察到Knight位移$K$的减小，这与超导状态下自旋极化的下降一致。在非应变样品中，我们的结果与以前的一些核磁共振工作相矛盾，也与以前关于Sr$_2$RuO$_4$序参量的最突出的建议相矛盾。讨论了可能的替代方案。
The superconducting state in the quasi-two-dimensional and strongly correlated Sr$_2$RuO$_4$ is uniquely held up as a solid state analog to superfluid $^3$He-$A$, with an odd-parity order parameter that also breaks time reversal symmetry, and for which the vector order parameter has the same direction in spin space for all electron momenta. The recent discovery that uniaxial pressure causes a steep rise and maximum in transition temperature ($T_c$) in strained samples motivated the study of $^{17}$O nuclear magnetic resonance (NMR) that we describe in this article. A reduction of Knight shifts $K$ was observed for all strain values and temperatures $T<T_c$, consistent with a drop in spin polarization in the superconducting state. In unstrained samples, our results are in contradiction with a body of previous NMR work, and with the most prominent previous proposals for the order parameter of Sr$_2$RuO$_4$. Possible alternative scenarios are discussed.