Charge-order-maximized momentum-dependent superconductivity
Charge-order-maximized momentum-dependent superconductivity
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DOI：
10.1038/nphys699
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发表时间：
2007-10-01
期刊：
影响因子：
19.6
通讯作者：
Takagi, H.
中科院分区：
文献类型：
--
作者：
Kiss, T.;Yokoya, T.;Takagi, H.
电荷有序和超导电性被观察到的相图中的各种材料，如NbSe 3，层状过渡金属二硫属化物和高温氧化铜超导体，低维有机物，Ba 1-xKxBiO 3等。虽然传统的电荷密度波（CDW）和超导转变都在费米能级（E F）的单粒子态密度中显示出能隙，但它们的物理性质是截然不同的：CDW的绝缘行为和超导体的零电阻率。因此，这两种基态被认为是相互竞争的。在这里，我们提供的证据，最大化的超导电性在动量（k）空间中的点，直接连接的CDW有序矢量。2 H-NbSe 2在CDW和超导跃迁（T-CDW分别类似于33 K和Tc = 7.2K）上的温度依赖角分辨光电子能谱表明，在相同的费米面交叉点k处，CDW引起的谱重耗尽演化为最大的超导能隙。这些k点也显示出最高的电子-声子耦合和最低的费米速度。我们的研究结果表明，在电子-声子耦合系统中，电荷有序可以增强超导电性，与普遍认为它只与超导电性竞争的观点形成直接对比。
Charge ordering and superconductivity are observed in the phase diagrams of a variety of materials such as NbSe3, layered transition-metal dichalcogenides and high-temperature copper oxide superconductors, low-dimensional organics, Ba1-xKxBiO3 and so forth. Although both conventional charge-density-wave (CDW) and superconducting transitions show an energy gap in the single-particle density of states at the Fermi level ( E F), their physical properties are poles apart: insulating behaviour for the CDW and zero resistivity in superconductors. Consequently, these two ground states are believed to compete with each other. Here we provide evidence for maximized superconductivity at points in momentum (k) space that are directly connected by the CDW ordering vector. Temperature-dependent angle-resolved photoemission spectroscopy of 2H-NbSe2 across the CDW and superconducting transitions ( T-CDW similar to 33Kand T-c= 7.2 K, respectively) shows CDW-induced spectral-weight depletion at the same Fermi-surface-crossing k points, which evolve into the largest superconducting gaps. These k points also show the highest electron-phonon coupling and lowest Fermi velocities. Our results demonstrate that charge order can boost superconductivity in an electron-phonon coupled system, in direct contrast to the prevailing view that it only competes with superconductivity.