Plasmon modes in double-layer gapped graphene at zero temperature

• Published in: Physics letters. A 2020-04, Vol.384 (10), p.126221, Article 126221
• Main Authors: Men, Nguyen Van, Phuong, Dong Thi Kim
• Format: Article
• Language: English
• Subjects: Collective excitations; Gapped graphene; Zero temperature
• ISSN: 0375-9601; 1873-2429
• DOI: 10.1016/j.physleta.2019.126221

•There are two plasmon modes in the system.•Analytical expressions of plasmon frequencies depend on band gap.•The increasing band gap decreases plasmon frequencies of two modes.•Effects of separation and carrier density on plasmon are seemly independent to small band gap. Plasmon dispersions and damping rate of plasma oscillations in a double-layer gapped graphene made of two parallel mono layer gapped graphene sheets grown on dielectric separation are calculated within random-phase-approximation at zero temperature. By using long wavelength limit expansion, analytical expressions for optical and acoustic plasmon frequencies have been formed, and the formulae demonstrate that the considerable difference in analytical form for plasmon frequencies comes from the factor depending on the band gap, compared to gapless situation. Numerical results show that only large band gap decreases remarkably plasmon frequencies of two modes in the range of large wave vector. Acoustic plasmon branch becomes shorter than that in case of zero gap while optical one seems independent with small band gap. In addition, interlayer separation and carrier density affect on collective excitations and damping rate when taking into account the band gap quite similarly to those in case of zero gap.