Ultra-long wavelength Dirac plasmons in graphene capacitors

Abstract

Graphene is a valuable 2D platform for plasmonics as illustrated in recent THz and mid-infrared optics experiments. These high-energy plasmons however, couple to the dielectric surface modes giving rise to hybrid plasmon-polariton excitations. Ultra-long wavelengths address the low energy end of the plasmon spectrum, in the GHz-THz electronic domain, where intrinsic graphene Dirac plasmons are essentially decoupled from their environment. However experiments are elusive due to the damping by ohmic losses at low frequencies. We demonstrate here a plasma resonance capacitor (PRC) using hexagonal boron-nitride (hBN) encapsulated graphene at cryogenic temperatures in the near-ballistic regime. We report on a 100 μm quarter-wave plasmon mode, at 40 GHz, with a quality factor Q;2. The accuracy of the resonant technique yields a precise determination of the electronic compressibility and kinetic inductance, allowing to assess residual deviations from intrinsic Dirac plasmonics. Our GHz frequency capacitor experiment constitutes a first step towards the demonstration of plasma resonance transistors for microwave detection in the sub-THz domain for wireless communication and sensing. It also paves the way to the realization of doping-modulated superlattices where plasmon propagation is controlled by Klein tunneling. Two-dimensional electron systems (2DES) sustain both single-particle and collective low-energy excitations, the latter being called plasmons. In graphene, their interplay is controlled by the electron density n which rules the kinetic energy, interactions and damping. Free 2DES plasmons are dispersive with q p

Resonant terahertz detection using graphene plasmons

“…Elimination of these damping channels, e.g. with Schottky/tunnel contacts and lowimpedance antennas, may extend the resonant detection down to tens of gigahertz 45 . Other dissipation channels such as electron viscosity 46,47 and interband absorption 18 should be most pronounced at higher-order harmonics and in the vicinity of the NP, as opposed to the data in Fig.…”

Dynamical Separation of Bulk and Edge Transport in HgTe-Based 2D Topological Insulators

“…As depicted in Fig.1d, dissipation results from the access resistance R c and the finite sheet resistance R = RL of the HgTe. For frequencies exceeding the charge relaxation frequency 1/2πRC t of the device, typically 1 GHz for L = 10 µm, the capacitors then host evanescent waves [17,21,27], driven by the resistance of the HgTe film. Assuming translation invariance along the transverse axis, the admittance of the capacitor reads [19]:…”

RF compressibility of topological surface and interface states in metal–hBN–Bi2Se3 capacitors

“…This introduces impurities-possibly an air or vacuum layer between the hBN and Bi 2 Se 3 -and reduces the dielectric constant of the gate dielectric. In CAP2, c g yields the dielectric constant of hBN that is recognized in the literature ( 3.2 k » ) [7,21,22]. The data in figure 3(c) also allows us to extract the chemical potential at the gated surface using the Berglund integral [6]:…”

“…Radio frequency (RF) transport has been widely used to characterize various low-dimensional systems including graphene [1][2][3][4][5][6][7][8] and to detect and manipulate edge states via interferometric techniques [9][10][11]. Such techniques have recently gained importance in the context of the detection of coherent and topological states that are useful for quantum computing [9,12].…”