Alloul H, Wzietek P, Mito T, Pontiroli D, Aramini M, Riccò M, Itie J P, Elkaim E
Laboratoire de Physique des Solides, CNRS, Université Paris-Sud, Université Paris-Saclay, 91405 Orsay, France.
CNISM and Dipartimento di Fisica, Università di Parma-Via G.P. Usberti 7/a, 43100 Parma, Italy.
Phys Rev Lett. 2017 Jun 9;118(23):237601. doi: 10.1103/PhysRevLett.118.237601. Epub 2017 Jun 5.
We present a detailed NMR study of the insulator-to-metal transition induced by an applied pressure p in the A15 phase of Cs_{3}C_{60}. We evidence that the insulating antiferromagnetic (AFM) and superconducting (SC) phases coexist only in a narrow p range. At fixed p, in the metallic state above the SC transition T_{c}, the ^{133}Cs and ^{13}C NMR spin-lattice relaxation data are seemingly governed by a pseudogaplike feature. We prove that this feature, also seen in the ^{133}Cs NMR shift data, is rather a signature of the Mott transition which broadens and smears out progressively for increasing (p,T). The analysis of the variation of the quadrupole splitting ν_{Q} of the ^{133}Cs NMR spectrum precludes any cell symmetry change at the Mott transition and only monitors a weak variation of the lattice parameter. These results open an opportunity to consider theoretically the Mott transition in a multiorbital three-dimensional system well beyond its critical point.
我们展示了一项关于在Cs₃C₆₀的A15相中施加压力p所诱导的绝缘体到金属转变的详细核磁共振（NMR）研究。我们证明绝缘反铁磁（AFM）相和超导（SC）相仅在狭窄的压力范围内共存。在固定压力p下，在高于超导转变温度Tc的金属态中，¹³³Cs和¹³C NMR自旋 - 晶格弛豫数据似乎受类似赝能隙特征的支配。我们证明，在¹³³Cs NMR位移数据中也可见的这一特征，实际上是莫特转变的一个标志，随着（p，T）的增加，它会逐渐变宽并模糊。对¹³³Cs NMR谱的四极分裂νQ变化的分析排除了在莫特转变时任何晶胞对称性的变化，并且仅监测到晶格参数的微弱变化。这些结果为在远超临界点的多轨道三维系统中从理论上考虑莫特转变提供了契机。
