Commensurate to Incommensurate Transition of Three Dimensional Charge Density Waves

Abstract: Charge density wave (CDW) is a widely concerned emergent phenomenon in condensed matter physics. To establish a systematic understanding of CDW, we develop a diagrammatic self-consistent-field approach for cubic Holstein model employing fluctuation exchange approximation, and explore the emergence and transition of three-dimensional CDWs. Commensurate CDW (c-CDW) locked at $(\pi,\pi,\pi)$ is favored near half-filling, and the transition temperature is predicted around half of the nearest-neighbor hopping. Large hole doping leads to a suppression of CDW transition temperature and the emergence of incommensurate CDW (i-CDW), which is evidenced by a drifting of the ordering vector away from $(\pi,\pi,\pi)$ towards $(\pi,\pi,0)$. Phonon frequency significantly impacts the transition temperature and the phase boundary between c-CDW and i-CDW, and the optimal frequency for enlarging the CDW regime is also predicted near half of the nearest-neighbor hopping. These new theoretical results provide a systematic understanding of CDW and a fresh perspective on emergent phenomena dominated by electron-phonon interaction.