Murakami Yuta, Werner Philipp, Tsuji Naoto, Aoki Hideo
Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033, Japan.
Department of Physics, University of Fribourg, 1700 Fribourg, Switzerland.
Phys Rev Lett. 2014 Dec 31;113(26):266404. doi: 10.1103/PhysRevLett.113.266404. Epub 2014 Dec 24.
We reveal that electron-phonon systems described by the Holstein model on a bipartite lattice exhibit, away from half filling, a supersolid (SS) phase characterized by coexisting charge order (CO) and superconductivity (SC), and an accompanying quantum critical point (QCP). The SS phase, demonstrated by the dynamical mean-field theory with a quantum Monte Carlo impurity solver, emerges in the intermediate-coupling regime, where the peak of the Tc dome is located and the metal-insulator crossover occurs. On the other hand, in the weak- and strong-coupling regimes the CO-SC boundary is of first order with no intervening SS phases. The QCP is associated with the continuous transition from SS to SC and characterized by a reentrant behavior of the SS around it. We further show that the SS-SC transition is hallmarked by diverging charge fluctuations and a kink (peak) in the superfluid density.
我们揭示，在二分晶格上由霍尔斯坦模型描述的电子 - 声子系统，在远离半填充时，呈现出一种超固体（SS）相，其特征为共存的电荷序（CO）和超导性（SC），以及一个伴随的量子临界点（QCP）。通过具有量子蒙特卡罗杂质求解器的动态平均场理论证明，SS相出现在中间耦合区域，该区域是Tc穹顶的峰值所在之处且发生金属 - 绝缘体转变。另一方面，在弱耦合和强耦合区域，CO - SC边界是一级的，不存在中间的SS相。QCP与从SS到SC的连续转变相关联，其特征是围绕它的SS具有重入行为。我们进一步表明，SS - SC转变的标志是电荷涨落发散和超流密度中的一个扭结（峰值）。
