Taguchi Y, Kitora A, Iwasa Y
Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
Phys Rev Lett. 2006 Sep 8;97(10):107001. doi: 10.1103/PhysRevLett.97.107001. Epub 2006 Sep 6.
We revealed a detailed phase diagram of the very lightly doped regime in Li-intercalated superconductors, LixZrNCl, to which previous studies have never gained access owing to the difficulty in synthesizing single-phase samples. A continuous and uniform Li intercalation without any indication of phase separation was carefully confirmed by means of synchrotron x-ray diffraction and Raman scattering experiments. Upon reducing the carrier density below x=0.12, we found a rapid increase in the superconducting transition temperature (Tc) immediately followed by the superconductor-to-insulator transition (SIT). Such an increase in Tc on the verge of SIT seems to be difficult to explain by the conventional theory, but may be indicative of the charge fluctuation contribution to superconductivity in low-carrier-density systems.
我们揭示了锂插层超导体LixZrNCl中极轻掺杂区域的详细相图，由于合成单相样品存在困难，以往的研究从未涉足该区域。通过同步辐射X射线衍射和拉曼散射实验，我们仔细确认了锂的连续且均匀的插层过程，未发现任何相分离迹象。当载流子密度降至x = 0.12以下时，我们发现超导转变温度（Tc）迅速升高，紧接着出现超导体到绝缘体的转变（SIT）。在SIT边缘的这种Tc升高似乎难以用传统理论解释，但可能表明在低载流子密度系统中，电荷涨落对超导性有贡献。
