Shibauchi Takasada, Krusin-Elbaum Lia, Hasegawa Masashi, Kasahara Yuichi, Okazaki Ryuji, Matsuda Yuji
Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
Proc Natl Acad Sci U S A. 2008 May 20;105(20):7120-3. doi: 10.1073/pnas.0712292105. Epub 2008 May 14.
In high-transition-temperature (T(c)) superconductivity, charge doping is a natural tuning parameter that takes copper oxides from the antiferromagnet to the superconducting region. In the metallic state above T(c), the standard Landau's Fermi-liquid theory of metals as typified by the temperature squared (T(2)) dependence of resistivity appears to break down. Whether the origin of the non-Fermi-liquid behavior is related to physics specific to the cuprates is a fundamental question still under debate. We uncover a transformation from the non-Fermi-liquid state to a standard Fermi-liquid state driven not by doping but by magnetic field in the overdoped high-T(c) superconductor Tl(2)Ba(2)CuO(6+x). From the c-axis resistivity measured up to 45 T, we show that the Fermi-liquid features appear above a sufficiently high field that decreases linearly with temperature and lands at a quantum critical point near the superconductivity's upper critical field-with the Fermi-liquid coefficient of the T(2) dependence showing a power-law diverging behavior on the approach to the critical point. This field-induced quantum criticality bears a striking resemblance to that in quasi-two-dimensional heavy-Fermion superconductors, suggesting a common underlying spin-related physics in these superconductors with strong electron correlations.
在高温转变温度（(T_c)）超导中，电荷掺杂是一种自然的调节参数，它能使铜氧化物从反铁磁体转变到超导区域。在高于(T_c)的金属态中，以电阻率与温度平方（(T^2)）相关为典型特征的标准朗道金属费米液体理论似乎失效了。非费米液体行为的起源是否与铜酸盐特有的物理性质有关，仍是一个仍在争论的基本问题。我们发现在过掺杂的高温超导体(Tl_2Ba_2CuO_{6 + x})中，从非费米液体态到标准费米液体态的转变不是由掺杂驱动，而是由磁场驱动。通过测量高达45 T的(c)轴电阻率，我们表明费米液体特征出现在一个足够高的场强之上，该场强随温度线性下降，并在超导上临界场附近的一个量子临界点处达到——(T^2)依赖关系的费米液体系数在接近临界点时呈现幂律发散行为。这种场诱导的量子临界性与准二维重费米子超导体中的情况惊人地相似，这表明在这些具有强电子关联的超导体中存在共同的与自旋相关的潜在物理机制。
