arXiv subjects

Wojciech Julian Pasek

Publications and source records attributed to Wojciech Julian Pasek.

6 recordsLinked to original sources

arXiv2026

Tunable Electron Quantum Optics in Graphene Slit Junctions

A graphene slit junction is investigated as a compact geometry for directional electron-beam formation, coherent interference, and symmetry-controlled spin filtering. Atomistic tight-binding calculations combined with the nonequilibrium Green's function formalism show that trigonal warping in monolayer graphene produces strongly directional electron beams near E~2.7eV. Boundary reflections redirect these beams toward a common drain, where the transmission exhibits magnetic flux-dependent oscillations consistent with an h/e Aharonov-Bohm period, whose modulation is characterized by Fourier analysis and harmonic fitting. A local electrostatic gate provides additional control of the interference phase. In separate self-consistent mean-field Hubbard calculations, the pristine antiferromagnetic ground state is shown to have spin-degenerate transmission, whereas structural or electrostatic breaking of the left-right symmetry enables spin filtering. Complementary valley-resolved calculations using a four-band continuum model demonstrate analogous beam formation in bilayer graphene at E = 50meV. The results identify the slit junction as a common geometry for electron-optical and spin-dependent transport and motivate further investigation of low-energy bilayer implementations.

cond-mat.mes-hall↗

arXiv2025

Multisubband Plasmons in InAs/GaSb Broken Gap Quantum Well

Multi-subband plasmon (MSP) modes in heavily doped InAs/GaSb broken-gap quantum wells grown via molecular beam epitaxy (MBE) are investigated. An $8$-band $\vec{k} \cdot \vec{p}$ semiclassical model accurately predicts ellipsometric spectra, reflecting strong subband hybridization and non-parabolicity. In contrast, single-band plasmon models show qualitative discrepancies with experiment, even with adjusted effective masses. These findings highlight the potential of broken-gap wells for quantum technologies leveraging interband coupling and wavefunction hybridization.

cond-mat.mes-hall↗

arXiv2023

THz ultra-strong light-matter coupling up to 200K with continuously-graded parabolic quantum wells

Continuously graded parabolic quantum wells with excellent optical performances are used to overcome the low-frequency and thermal limitations of square quantum wells at terahertz frequencies. The formation of microcavity intersubband polaritons at frequencies as low as 1.8 THz is demonstrated, with a sustained ultra-strong coupling regime up to a temperature of 200K. It is additionally shown that the ultra-strong coupling regime is preserved when the active region is embedded in sub-wavelength resonators, with an estimated relative strength $η= Ω_R / ω_0 = 0.12$. This represents an important milestone for future studies of quantum vacuum radiation because such resonators can be optically modulated at ultrafast rates, possibly leading to the generation of non-classical light via the dynamic Casimir effect. Finally, with an effective volume of $2.10^{-6} λ_0^3$, it is estimated that fewer than 3000 electrons per resonator are ultra-strongly coupled to the quantized electromagnetic mode, proving it is also a promising approach to explore few-electron polaritonic systems operating at relatively high temperatures.

physics.optics↗

arXiv2022

Towards an effective mass model for the quasi-1D magnesium diboride superconducting nanostructures

We developed a parabolic effective mass model with the aim to describe the in-plane constricted superconductivity in few-monolayer MgB$_2$. The model was employed to study a constricted quasi-$1$D superlattice with the simplest version of the Anderson approximation. Resonant Fano-Feshbach-like effect was found, between a miniband of a continuous normal state dispersion cutting across $E_F$ and a miniband of quasi-discrete dispersion, even though the latter is significantly energetically distanced from the Fermi level. The origin of the phenomenon was identified to be the presence of characteristic strongly localised eigenstates, due to the specific material parameters. Moreover, the mechanism leading to a "precursor" pseudogap region in a system with a non-zero phase difference is described, when the strength of the coupling is still not sufficient to open a superconducting gap, but enough to introduce electron-hole mixing into the system.

cond-mat.supr-con↗

arXiv2017

Application of the Landau-Zener-Stueckelberg-Majorana dynamics in an electrically driven flip of a hole spin

An idea of employing the Landau-Zener-Stückelberg-Majorana (LZSM) dynamics to flip a spin of a single ground state hole is introduced and explored by a time-dependent simulation. This configuration interaction study considers a hole confined in a quantum molecule formed in InSb $\langle111\rangle$ quantum wire by application of an electrostatic potential. An up-down spin-mixing avoided crossing is formed by non-axial terms in the Kohn-Luttinger Hamiltonian and the Dresselhaus spin-orbit one. Manipulation of the system is possible by dynamic change of external vertical electric field, which enables the consecutive driving of the hole through two anticrossings. Moreover, a simple model of the power-law type noise that impedes the precise electric control of the system is included in the form of Random Telegraph Noise to estimate the limitations of the working conditions. We show that in principle the process is possible, but it requires a precise control of parameters of the driving impulse.

cond-mat.mes-hall↗

arXiv2016

The Coulomb-interaction-induced breaking of the Aufbau principle for hole charging of InGaAs/GaAs quantum dots

The so called "incomplete hole shell filling" phenomenon, that is the breaking of the Aufbau principle was reported by D. Reuter et al., [Phys. Rev. Lett. 94, 026808] in the hole charging spectra of quantum dot when results were interpreted in context of s/p/d shell system - typical for electrons. We report an example of inter-particle-interaction induced Aufbau principle violation even if it is applied to one-particle Kohn-Luttinger eigenstates. We present a k-dot-p/configuration-interaction study that concerns multiple holes confined in InGaAs/GaAs self-assembled cylindrical quantum dot. Eigenenergies and eigenvectors of up to six hole ground states were obtained - along with corresponding one-hole orbital occupations - and discussed in context of the Aufbau principle. PACS numbers: 73.21.La, 81.07.Ta, 71.70.Gm

cond-mat.mes-hall↗