Plasmon dispersion and Landau damping in the nonlinear quantum regime

We study the dispersion properties of electron plasma waves, or plasmons, which can be excited in quantum plasmas in the nonlinear regime. In order to describe nonlinear electron response to finite amplitude plasmons, we apply the Volkov approach to nonrelativistic electrons. For that purpose, we use the Schrödinger equation and describe the electron population of a quantum plasma as a mixture of quantum states. Within the kinetic framework that we are able to derive from the Volkov solutions, we discuss the role of the wave amplitude on the nonlinear plasma response. Finally, we focus on the quantum properties of nonlinear Landau damping and study the contributions of multiplasmon absorption and emission processes.

Bulk plasmon-limited mobility in semiconductors: from bulk to nanowires

Analytical expressions are obtained for the low-field mobility in semiconductors for scattering of three-dimensional (3D), two-dimensional (2D), and one-dimensional (1D) charged carriers by bulk plasmons. The consideration is based on the quantum kinetic equation and model distribution function in form of a shifted Fermi distribution and includes calculations of the dielectric function of 3D, 2D and 1D carriers in the random phase approximation. The resulting analytical expressions give dependences of the plasmon limited mobility on the dimensionality of charge carrier system, their density, effective mass, temperature and confining dimensions. The plasmon limited mobility decreases as the dimensionality of the electron gas D decreases. The physical reason for this is an increase in the absolute value of the cutoff vector with a decrease in D. Comparison of our calculations with known experimental data shows that relative contribution of the electron-plasmon scattering to total mobility reaches a maximum in the temperature range 10-100 K and can be a few percent in bulk crystals, ten of percent in quantum wells, and is close to the experimental values in nanowires. A noticeable effect of the scattering 3D, 2D and 1D electrons by bulk plasmons on mobility is expected in semiconductors with a sufficiently high mobility of more than 105cm2V-1s.

Specific Heat of Electron Plasma Waves

Collective modes in a plasma, like phonons in a solid, contribute to a material's equation of state and transport properties, but the long wavelengths of these modes are difficult to simulate with today's finite-size quantum simulation techniques. A simple Debye-type calculation of the specific heat of electron plasma waves is presented, yielding up to 0.05k/e^{-} for warm dense matter (WDM), where thermal and Fermi energies are near 1  Ry=13.6  eV. This overlooked energy reservoir is sufficient to explain reported compression differences between theoretical hydrogen models and shock experiments. Such an additional specific heat contribution refines our understanding of systems passing through the WDM regime, such as the convective threshold in low-mass main-sequence stars, white dwarf envelopes, and substellar objects; WDM x-ray scattering experiments; and the compression of inertial confinement fusion fuels.

Polarization-dependent excitons and plasmon activity in nodal-line semimetal ZrSiS

The optical properties of the bulk ZrSiS nodal-line semimetal are theoretically studied within a many-body formalism. The G₀W₀ bands are similar to those calculated within the density functional theory, except near the Γ-point; in particular, no significant differences are found around the Fermi energy. On the other hand, the solution of the Bethe-Salpeter equation reveals significant excitonic activity, mostly as dark excitons which appear in a wide energy range. Bright excitons, in contrast, are less numerous, but their location and intensity depend greatly on the polarization of the incident electric field, as the absorption coefficient itself does. The binding energy of these excitons correlates well with their spatial distribution functions. In any case, good agreement with the available experimental data for absorption/reflection is achieved. Finally, the possible activation of plasma oscillations is investigated. Plasmons may be formed at low energies, but they are damped and decayed producing electron-hole pairs, more importantly for q along the Γ-M path.

Efficient plasmonic emission by the quantum Čerenkov effect from hot carriers in graphene

Graphene plasmons have been found to be an exciting plasmonic platform, thanks to their high field confinement and low phase velocity, motivating contemporary research to revisit established concepts in light-matter interaction. In a conceptual breakthrough over 80 years old, Čerenkov showed how charged particles emit shockwaves of light when moving faster than the phase velocity of light in a medium. To modern eyes, the Čerenkov effect offers a direct and ultrafast energy conversion scheme from charge particles to photons. The requirement for relativistic particles, however, makes Čerenkov emission inaccessible to most nanoscale electronic and photonic devices. Here we show that graphene plasmons provide the means to overcome this limitation through their low phase velocity and high field confinement. The interaction between the charge carriers flowing inside graphene and the plasmons enables a highly efficient two-dimensional Čerenkov emission, giving a versatile, tunable and ultrafast conversion mechanism from electrical signal to plasmonic excitation.

Theory and computation of hot carriers generated by surface plasmon polaritons in noble metals

Hot carriers (HC) generated by surface plasmon polaritons (SPPs) in noble metals are promising for application in optoelectronics, plasmonics and renewable energy. However, existing models fail to explain key quantitative details of SPP-to-HC conversion experiments. Here we develop a quantum mechanical framework and apply first-principles calculations to study the energy distribution and scattering processes of HCs generated by SPPs in Au and Ag. We find that the relative positions of the s and d bands of noble metals regulate the energy distribution and mean free path of the HCs, and that the electron-phonon interaction controls HC energy loss and transport. Our results prescribe optimal conditions for HC generation and extraction, and invalidate previously employed free-electron-like models. Our work combines density functional theory, GW and electron-phonon calculations to provide microscopic insight into HC generation and ultrafast dynamics in noble metals.

Phase-space structures in quantum-plasma wave turbulence

The quasilinear theory of the Wigner-Poisson system in one spatial dimension is examined. Conservation laws and properties of the stationary solutions are determined. Quantum effects are shown to manifest themselves in transient periodic oscillations of the averaged Wigner function in velocity space. The quantum quasilinear theory is checked against numerical simulations of the bump-on-tail and two-stream instabilities. The predicted wavelength of the oscillations in velocity space agrees well with the numerical results.