A Pathway to Efficient Simulations of Charge Density Waves in Transition Metal Dichalcogenides: A Case Study for TiSe2
arxiv(2024)
摘要
Charge density waves (CDWs) in transition metal dichalcogenides are the
subject of growing scientific interest due to their rich interplay with exotic
phases of matter and their potential technological applications. Here, using
density functional theory with advanced meta-generalized gradient
approximations (meta-GGAs) and linear response time-dependent density
functional theory (TDDFT) with state-of-the-art exchange-correlation kernels,
we investigate the electronic, vibrational, and optical properties in 1T-TiSe2
with and without CDW. In both bulk and monolayer TiSe2, the electronic bands
and phonon dispersions in either normal (semi-metallic) or CDW (semiconducting)
phase are described well via meta-GGAs, which separate the valence and
conduction bands just as HSE06 does but with significantly more computational
feasibility. Instead of the underestimated gap with standard
exchange-correlation approximations and the overestimated gap with screened
hybrid functional HSE06, the band gap of the monolayer TiSe2 CDW phase
calculated by the meta-GGA MVS (151 meV) is consistent with the angle-resolved
photoemission spectroscopy (ARPES) gap of 153 meV measured at 10 K. In
addition, the gap of bulk TiSe2 CDW phase reaches 67 meV within the TASK
approximation, close to the ARPES gap of 82 meV. Regarding excitations of
many-body nature, for bulk TiSe2 in normal and CDW phases, the experimentally
observed humps of electron energy loss spectroscopy and plasmon peak are
successfully reproduced in TDDFT, without an obvious kernel dependence. To
unleash the full scientific and technological potential of CDWs in transition
metal dichalcogenides, the chemical doping, heterostructure engineering, and
pump-probe techniques are needed. Our study opens the door to simulating these
complexities in CDW compounds from first principles by revealing meta-GGAs as
an accurate low-cost alternative to HSE06.
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