Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China.
Phys Rev Lett. 2019 Feb 22;122(7):077601. doi: 10.1103/PhysRevLett.122.077601.
The spontaneous generation of charge-density-wave order in a Dirac fermion system via the natural mechanism of electron-phonon coupling is studied in the framework of the Holstein model on the honeycomb lattice. Using two independent and unbiased quantum Monte Carlo methods, the phase diagram as a function of temperature and coupling strength is determined. It features a quantum critical point as well as a line of thermal critical points. Finite-size scaling appears consistent with fermionic Gross-Neveu-Ising universality for the quantum phase transition and bosonic Ising universality for the thermal phase transition. The critical temperature has a maximum at intermediate couplings. Our findings motivate experimental efforts to identify or engineer Dirac systems with sufficiently strong and tunable electron-phonon coupling.
在蜂窝晶格的 Holstein 模型框架内，通过电子-声子耦合的自然机制，研究了狄拉克费米子系统中电荷密度波有序的自发产生。使用两种独立且无偏的量子蒙特卡罗方法，确定了温度和耦合强度作为函数的相图。它具有量子临界点以及热临界点线。有限大小的标度与量子相变的费米 Gross-Neveu-Ising 普遍性以及热相变的玻色 Ising 普遍性一致。临界温度在中等耦合时具有最大值。我们的发现促使人们努力识别或设计具有足够强和可调谐电子-声子耦合的狄拉克系统。
