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Pressure-induced Mott-insulator–metal crossover at ambient temperature in an overexpanded fulleride†
Materials Chemistry Frontiers ( IF 6.0 ) Pub Date : 2018-03-14 00:00:00 , DOI: 10.1039/c8qm00048d Ruth H. Zadik 1, 2, 3, 4 , Yasuhiro Takabayashi 5, 6, 7, 8 , Ross H. Colman 1, 2, 3, 4 , Gaston Garbarino 9, 10, 11 , Kosmas Prassides 5, 6, 7, 8
Materials Chemistry Frontiers ( IF 6.0 ) Pub Date : 2018-03-14 00:00:00 , DOI: 10.1039/c8qm00048d Ruth H. Zadik 1, 2, 3, 4 , Yasuhiro Takabayashi 5, 6, 7, 8 , Ross H. Colman 1, 2, 3, 4 , Gaston Garbarino 9, 10, 11 , Kosmas Prassides 5, 6, 7, 8
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Rb0.5Cs2.5C60 is a member of the family of face-centred-cubic (fcc)–structured alkali fullerides, A3C60 (A = alkali metal) with a highly expanded lattice size. At ambient temperature and pressure, it is a Mott–Jahn–Teller insulator. However, upon cooling it exhibits first a crossover to an anomalous metallic state (Jahn–Teller metal) in the vicinity of 90 K followed next by a transition to a bulk superconductor with a transition temperature, Tc of 29.4 K. Here we study its structural and electronic response to the application of pressure. Synchrotron X-ray powder diffraction at ambient temperature shows that the same Mott-insulator–metal electronic state crossover can be induced through pressure application under isothermal conditions, as evidenced by a distinct broad symmetry-preserving compressibility anomaly, which sets in at ∼0.4 GPa and extends to ∼0.75 GPa. Complementary magnetic susceptibility measurements also reveal that the crossover temperature, T′ tunable at ambient pressure through adjusting the dopant ratio to vary the unit cell volume, can be controlled through pressure application and be mapped onto the same global electronic phase diagram. The observed electronic response, as a function of both physical and ‘chemical’ pressure, is thus of the same electronic origin, namely the control of the bandwidth, W via outer wave function overlap of the constituent fulleride ions.
中文翻译：
压力引起的莫特-绝缘子-金属在环境温度下在过膨胀的富勒烯中的交叉现象†
Rb 0.5 Cs 2.5 C 60是面心立方（fcc）结构的碱金属全碱金属族的成员，A 3 C 60（A =碱金属），晶格尺寸高。在环境温度和压力下，它是Mott–Jahn–Teller绝缘子。然而，在冷却时，它首先在90 K附近表现出向异常金属态（Jahn–Teller金属）的转变，然后转变为转变温度为T c的体超导体29.4K。这里我们研究其对压力施加的结构和电子响应。室温下的同步加速器X射线粉末衍射表明，通过在等温条件下施加压力，可以引起相同的Mott-绝缘体-金属电子态交叉，这一点由一个明显的，广泛的对称性可压缩性异常证明，该异常性设置为〜0.4 GPa并扩展至约0.75 GPa。互补的磁化率测量结果还表明，交叉温度T通过调节掺杂剂比例来改变晶胞体积，可在环境压力下对其进行调节，可通过施加压力对其进行控制，并将其映射到同一全局电子相图上。因此，所观察到的作为物理压力和“化学”压力的函数的电子响应具有相同的电子起源，即通过组成的富勒离子的外波函数重叠来控制带宽W。
更新日期：2018-03-14
中文翻译：
压力引起的莫特-绝缘子-金属在环境温度下在过膨胀的富勒烯中的交叉现象†
Rb 0.5 Cs 2.5 C 60是面心立方（fcc）结构的碱金属全碱金属族的成员，A 3 C 60（A =碱金属），晶格尺寸高。在环境温度和压力下，它是Mott–Jahn–Teller绝缘子。然而，在冷却时，它首先在90 K附近表现出向异常金属态（Jahn–Teller金属）的转变，然后转变为转变温度为T c的体超导体29.4K。这里我们研究其对压力施加的结构和电子响应。室温下的同步加速器X射线粉末衍射表明，通过在等温条件下施加压力，可以引起相同的Mott-绝缘体-金属电子态交叉，这一点由一个明显的，广泛的对称性可压缩性异常证明，该异常性设置为〜0.4 GPa并扩展至约0.75 GPa。互补的磁化率测量结果还表明，交叉温度T通过调节掺杂剂比例来改变晶胞体积，可在环境压力下对其进行调节，可通过施加压力对其进行控制，并将其映射到同一全局电子相图上。因此，所观察到的作为物理压力和“化学”压力的函数的电子响应具有相同的电子起源，即通过组成的富勒离子的外波函数重叠来控制带宽W。
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