arXiv subjects

Zhanna Devizorova

Publications and source records attributed to Zhanna Devizorova.

5 recordsLinked to original sources

arXiv2026

Unconventional quantization of 2D plasmons in cavities formed by gate slots

We demonstrate that the slot between parallel metal gates placed above two-dimensional electron system (2DES) forms a plasmonic cavity with unconventional mode quantization. The resonant plasmon modes are excited when the slot width $L$ and the plasmon wavelength $λ$ satisfy the condition $L = λ/8 +n \times λ/2$, where $n=0, 1, 2 \ldots$. The lowest resonance occurs at a surprisingly small cavity size, specifically one eighth of the plasmon wavelength, which contrasts with the conventional half-wavelength Fabry-Perot cavities in optics. This unique quantization rule arises from a non-trivial phase shift of $-π/4$ acquired by the 2D plasmon upon reflection from the edge of the gate. The slot plasmon modes exhibit weak decay into the gated 2DES region, with the decay rate being proportional to the square root of the separation between the gate and the 2DES. Absorption cross-section by such slots reaches $\sim 50$ % of the fundamental dipole limit without any matching strategies, and is facilitated by field enhancement at the metal edges.

cond-mat.mes-hall↗

arXiv2024

Photon drag at the junction between metal and 2d semiconductor

Photon drag represents a mechanism of photocurrent generation wherein the electromagnetic (EM) field momentum is transferred directly to the charge carriers. It is believed to be small by the virtue of low photon momentum compared to the typical momenta of the charge carriers. Here, we show that photon drag becomes particularly strong at the junctions between metals and 2d materials, wherein highly non-uniform local EM fields are generated upon diffraction. To this end, we combine an exact theory of diffraction at 'metal-2d material' junctions with microscopic transport theory of photon drag, and derive the functional dependences of the respective photovoltage on the parameters of EM field and 2d system. The voltage responsivity appears inversely proportional to the electromagnetic frequency $ω$, the sheet density of charge, and a dimensionless momentum transfer coefficient $α$ which depends only on 2d conductivity in units of light speed $η= 2πσ/c$ and light polarization. For $p$-polarized incident light, the momentum transfer coefficient appears finite even for vanishingly small 2d conductivity $η$, which is a consequence of dynamic lightning rod effect. For $s$-polarized incident light, the momentum transfer coefficient scales as $η\ln η^{-1}$, which stems from long-range dipole radiation of a linear junction. A simple estimate shows that the ratio of thermoelectric and photon drag photovoltages at the junction for $p$-polarization is roughly $ωτ_\varepsilon$, where $τ_\varepsilon$ is the energy relaxation time, while for $s$-polarization the photon drag always dominates over the thermoelectric effect.

cond-mat.mes-hall↗

arXiv2023

One-dimensional electron localization in semiconductors coupled to electromagnetic cavities

Electrical conductivity of one-dimensional (1d) disordered solids decays exponentially with their length, which is a celebrated manifestation of the localization phenomenon. Here, we study the modifications of localized conductivity induced by placement of 1d semiconductors inside of single-mode electromagnetic cavities, focusing on the regime of non-degenerate doping. We use the Green's function technique modified for the non-perturbative account of cavity excited states, and including both coherent electron-cavity effects (i.e. electron motion in the zero-point fluctuating field) and incoherent processes of photon emission upon tunneling. The energy spectrum of electron transmission in the cavity acquires Fano-type resonances associated with virtual photon emission, passage along the resonant level, and photon re-absorption. The quality factor of the Fano resonance depends on whether the intermediate state is coupled to the leads, and reaches its maximum when this state is localized deep in the disorder potential. Coupling to the cavity also elevates the energies of the shallow bound states, bringing them to the conduction band bottom. Such an effect leads to the enhancement of the low-temperature conductance.

cond-mat.mes-hall↗

arXiv2021

Spin-orbit coupling suppression and singlet-state blocking of spin-triplet Cooper pairs

An inhomogeneous magnetic exchange field at a superconductor/ferromagnet interface converts spin-singlet Cooper pairs to a spin-aligned (i.e. spin-polarized) triplet state. Although the decay envelope of such triplet pairs within ferromagnetic materials is well studied, little is known about their decay in non-magnetic metals and superconductors, and in particular in the presence of spin-orbit coupling (SOC). Here we investigate devices in which triplet supercurrents are injected into the s-wave superconductor Nb. In the normal state of Nb, triplet supercurrents decay over a distance of 5 nm, which is an order of magnitude smaller than the decay of spin singlet pairs due to the SOC interacting with the spin associated with triplet pairs. In the superconducting state of Nb, triplet supercurrents are not able to couple with the singlet wavefunction and thus blocked by the absence of available equilibrium states in the singlet gap. The results offer new insight into the dynamics between s-wave singlet and s-wave triplet states.

cond-mat.supr-con↗

arXiv2015

Emission and amplification of surface plasmons in resonant - tunneling van der Waals heterostructures

We predict a new mechanism of surface plasmon amplification in graphene-insulator-graphene van der Waals heterostructures. The amplification occurs upon the stimulated interlayer electron tunneling accompanied by the emission of a coherent plasmon. The quantum-mechanical calculations of the non-local high-frequency tunnel conductivity show that a relative smallness of the tunneling exponent can be compensated by a strong resonance due to the enhanced tunneling between electron states with collinear momenta in the neighboring graphene layers. With the optimal selection of the barrier layer, the surface plasmon gain due to the inelastic tunneling can compensate or even exceed the loss due to both Drude and interband absorption. The tunneling emission of the surface plasmons is robust against a slight twist of the graphene layers and might explain the electroluminescence from the tunnel-coupled graphene layers observed in the recent experiments.

cond-mat.mes-hall↗