arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2006.13239cond-mat.str-elcond-mat.supr-con
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掺杂诱导量子自旋霍尔绝缘体到超导体的转变

Doping-induced quantum spin Hall insulator to superconductor transition

Zhenjiu Wang, Yuhai Liu, Toshihiro Sato, Martin Hohenadler, Chong Wang, Wenan Guo, Fakher F. Assaad

摘要:

动态生成的量子自旋霍尔态的一个独特性质是Goldstone模式,其对应于自旋轨道耦合序参量的长波长波动,其拓扑Skyrmion激发携带电荷2 $e$。在这里考虑的模型中,当改变化学势时,我们观察到两个跃迁:s波超导序参量在临界化学势$μ_{c1}$处发展,对应于费米子对的激发能隙,在$μ_{c2}$处量子自旋霍尔态的SO(3)序参量消失。使用负符号的,大规模的量子蒙特卡罗模拟,我们表明,$μ_{c1}=μ_{c2}$在我们的精度-我们可以解决掺杂远离半填充到$δ= 0.0017$。与量子自旋霍尔序参量的波动相关的长度尺度增长到我们的最低掺杂,表明连续或弱一阶跃迁。与平均场的预期相反,掺杂与化学势的曲线不是线性的,如果过渡是连续的,则指示动态临界指数$z > 2$。

英文摘要:

A unique property of a dynamically generated quantum spin Hall state are Goldstone modes that correspond to the long-wavelength fluctuations of the spin-orbit coupling order parameter whose topological Skyrmion excitations carry charge 2$e$. Within the model considered here, upon varying the chemical potential, we observe two transitions: An s-wave superconducting order parameter develops at a critical chemical potential $μ_{c1}$, corresponding to the excitation gap of pairs of fermions, and at $μ_{c2}$ the SO(3) order parameter of the quantum spin Hall state vanishes. Using negative-sign-free, large-scale quantum Monte Carlo simulations, we show that $μ_{c1}=μ_{c2}$ within our accuracy -- we can resolve dopings away from half filling down to $δ= 0.0017$. The length scale associated with the fluctuations of the quantum spin Hall order parameter grows down to our lowest doping, suggesting either a continuous or a weakly first-order transition. Contrary to mean-field expectations, the doping versus chemical potential curve is not linear, indicating a dynamical critical exponent $z > 2$ if the transition is continuous.

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