Drastic Reduction of Plasmon Damping in Two-Dimensional Electron Disks

Abstract

The plasmon damping has been investigated using resonant microwave absorption of twodimensional electrons in disks with different diameters. We have found an unexpected drastic reduction of the plasmon damping in the regime of strong retardation. This finding implies large delocalization of retarded plasmon field outside the plane of the two-dimensional electron system. A universal relation between the damping of plasmon polariton waves and retardation parameter is reported.

Plasmons in the van der Waals charge-density-wave material 2H-TaSe2

“…For the relatively wide ribbons, the spectral weight of the firstorder plasmon is less than that of the second-order plasmon (see Fig. 2d), which is presumably transferred to the second-order plasmon due to the retardation effect 30,31 . Therefore, we focus on the relatively narrow ribbons whose the second-order plasmon peak is nearly diminishing.…”

“…2c, the peak width of the first-order plasmon is 552 cm −1 at 1.6 × 10 6 m −1 and increases to 3200 cm −1 at 5.2 × 10 7 m −1 . Due to the retardation effect 30,31 , the plasmon peak width at small wave vectors is less than its Drude scattering rate. At relatively large wave vectors, where the retardation effect is already negligible, the plasmon width gradually increases with the wave vector increases.…”

“…Plasmons at the flat dispersion region can exhibit low group velocity, strong light confinement and considerably large field enhancement15 , which holds promise for highly sensitive detection of local and non-local electronic structures.As shown in Fig.2c, the peak width of the first-order plasmon is 552 cm −1 at 1.6 × 10 6 m −1 and increases to 3200 cm −1 at 5.2 × 10 7 m −1 . Due to the retardation effect30,31 , the plasmon peak width at small wave vectors is less than its Drude scattering rate. At relatively large wave vectors, where the retardation effect is already negligible, the plasmon width gradually increases with the wave vector increases.…”

Two-dimensional plasmon induced by metal proximity

“…Such a reduction in plasmon resonant frequency for small wave vector values is a clear indication of hybridization between the plasma waves and the light. However, the magnitude of the observed hybridization far exceeds the level expected of the ordinary 2D plasmons [25][26][27]. According to theory for the ungated 2D plasmon, ∆ω/ω p ≈ A 2 /4, where A is a dimensionless retardation parameter defined as ratio of the plasmon frequency to that of light, given the same wave vector q = π/L [27].…”

“…However, the magnitude of the observed hybridization far exceeds the level expected of the ordinary 2D plasmons [25][26][27]. According to theory for the ungated 2D plasmon, ∆ω/ω p ≈ A 2 /4, where A is a dimensionless retardation parameter defined as ratio of the plasmon frequency to that of light, given the same wave vector q = π/L [27]. In essence, this parameter indicates the extent of the retardation effect.…”