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Plasmons at the LaAlO3/SrTiO3 interface and in the graphene- LaAlO3 / SrTiO3 double layer

Faridi, A ; Sharif University of Technology

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  1. Type of Document: Article
  2. DOI: 10.1103/PhysRevB.95.165419
  3. Abstract:
  4. We study plasmon modes of the two-dimensional electron gas residing at the interface of band insulators LaAlO3 and SrTiO3 (LAO/STO) and the plasmon excitations of graphene-LAO/STO double layer as well. Considering the electron-electron interaction within random phase approximation, we calculate the plasmon dispersions of both systems numerically and in the long-wavelength limit analytical expressions for collective modes are found. One optical mode and two (three) acoustic modes are predicted for the LAO/STO (graphene-LAO/STO) system where only the uppermost acoustic mode of both systems can emerge above the electron-hole continuum depending on the characteristics of each system. In the case of LAO/STO interface, thanks to the spatial separation between t2g orbitals, the upper acoustic mode might be undamped at the long-wavelength limit depending on the exact value of the dielectric constant of SrTiO3. Same as other double layer systems, the interlayer distance for the graphene-LAO/STO system plays a crucial role in damping the upper acoustic mode. Faster damping of all plasmon modes of the present double layer system in comparison with the ones with conventional two-dimensional electron gas instead of t2g electron gas is also found due to heavier effective masses of the gas and also stronger interlayer Coulomb interaction. © 2017 American Physical Society
  5. Keywords:
  7. Source: Physical Review B ; Volume 95, Issue 16 , 2017 ; 24699950 (ISSN)
  8. URL: https://journals.aps.org/prb/abstract/10.1103/PhysRevB.95.165419