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Tilt-induced kink in the plasmon dispersion of two-dimensional Dirac electrons

Jalali Mola, Z ; Sharif University of Technology | 2018

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  1. Type of Document: Article
  2. DOI: 10.1103/PhysRevB.98.195415
  3. Publisher: American Physical Society , 2018
  4. Abstract:
  5. The list of two-dimensional Dirac systems with a tilt in their Dirac cone spectrum is expanding, and now, in addition to the organic system α(BEDT-TTF)2I3, it includes the two-dimensional 8Pmmn-borophene sheet, which allows for controlled doping by the gate voltage. We analytically calculate the polarization function of tilted Dirac cone for an arbitrary tilt parameter, 0≤η<1, and arbitrary doping. This enables us to find two interesting plasmonic effects solely caused by the tilt. (i) In addition to the standard plasmon oscillations, a strong enough tilt induces an additional linearly dispersing overdamped branch of plasmons, which is strongly Landau damped due to overlap with a large density of intraband free particle-hole (PH) excitations. (ii) There appears a kink in the plasmon dispersion for any nonzero tilt parameter. The kink appears when the plasmon branch enters the interband continuum of PH excitations. This kink becomes most manifest for wave vectors perpendicular to the tilt direction and fades away by approaching the tilt direction. Experimental measurements of the wave vector and energy of the plasmonic kink, when combined with our analytic formula for the kink energy scale, allow for a direct experimental estimation of the tilt parameter. Furthermore, we find that, for a fixed chemical potential μ, the screening is significantly enhanced by bringing the tilt η close to 1. © 2018 American Physical Society
  6. Keywords:
  8. Source: Physical Review B ; Volume 98, Issue 19 , 2018 ; 24699950 (ISSN)
  9. URL: https://journals.aps.org/prb/abstract/10.1103/PhysRevB.98.195415