Département de Physique de la Matière Condensée, Université de Genève, 1211 Geneva, Switzerland.
Proc Natl Acad Sci U S A. 2013 Apr 9;110(15):5774-8. doi: 10.1073/pnas.1218846110. Epub 2013 Mar 27.
Cuprate high-Tc superconductors exhibit enigmatic behavior in the nonsuperconducting state. For carrier concentrations near "optimal doping" (with respect to the highest Tcs) the transport and spectroscopic properties are unlike those of a Landau-Fermi liquid. On the Mott-insulating side of the optimal carrier concentration, which corresponds to underdoping, a pseudogap removes quasi-particle spectral weight from parts of the Fermi surface and causes a breakup of the Fermi surface into disconnected nodal and antinodal sectors. Here, we show that the near-nodal excitations of underdoped cuprates obey Fermi liquid behavior. The lifetime τ(ω, T) of a quasi-particle depends on its energy ω as well as on the temperature T. For a Fermi liquid, 1/τ(ω, T) is expected to collapse on a universal function proportional to (ℏω)(2) + (pπk(B)T)(2). Magneto-transport experiments, which probe the properties in the limit ω = 0, have provided indications for the presence of a T(2) dependence of the dc (ω = 0) resistivity of different cuprate materials. However, Fermi liquid behavior is very much about the energy dependence of the lifetime, and this can only be addressed by spectroscopic techniques. Our optical experiments confirm the aforementioned universal ω- and T dependence of 1/τ(ω, T), with p ∼ 1.5. Our data thus provide a piece of evidence in favor of a Fermi liquid-like scenario of the pseudogap phase of the cuprates.
铜酸盐高温超导体在非超导状态下表现出神秘的行为。对于载流子浓度接近“最佳掺杂”（相对于最高 Tc）的情况，输运和光谱性质与朗道-费米液体不同。在最佳载流子浓度的莫特绝缘侧，对应于欠掺杂，赝能隙从费米面的部分区域去除准粒子谱权重，并导致费米面分裂成不连续的节点和反节点区域。在这里，我们表明欠掺杂铜酸盐的近节点激发遵循费米液体行为。准粒子的寿命 τ(ω, T)不仅取决于其能量 ω，还取决于温度 T。对于费米液体，预期 1/τ(ω, T)将塌缩到与 (ℏω)^(2) + (pπk(B)T)^(2)成正比的普适函数上。探测 ω = 0 极限下性质的磁输运实验已经提供了不同铜酸盐材料的直流（ω = 0）电阻率存在 T(2)依赖性的迹象。然而，费米液体行为在很大程度上与寿命的能量依赖性有关，这只能通过光谱技术来解决。我们的光学实验证实了 1/τ(ω, T)的上述普适 ω 和 T 依赖性，其中 p∼1.5。因此，我们的数据提供了支持赝能隙相的铜酸盐具有类似于费米液体的情景的证据。
