arXiv subjects

Zbyněk Šobáň

Publications and source records attributed to Zbyněk Šobáň.

4 recordsLinked to original sources

arXiv2026

Coherent regime of Kapitza-Dirac effect with electrons

Electron matter waves coherently diffract when passing through a periodic structure of light formed by two interfering light waves. In this so-called Kapitza-Dirac effect, the electron momentum changes due to absorption and emission of photons via stimulated Compton scattering. Until now, the effect has only been observed with low energy electrons due to the small momentum of a visible photon compared to the momentum of high energy electron leading to diffraction angles of 10^(-4) rad or smaller. We report on the observation of the Kapitza-Dirac effect in a scanning electron microscope using high energy (20 and 30 keV) electrons with de-Broglie wavelengths of 9 pm and 7 pm, respectively. The photon sidebands in the electron transverse momentum spectrum are detected in the convergent beam diffraction geometry using spatial filtering. As the coupling strength between the electrons and the light field increases, the sideband populations exhibit coherent, reversible oscillations among diffraction orders. The effect can serve as a coherent electron beam-splitter or a phase-plate in various types of electron microscopes.

quant-ph↗

arXiv2026

Coherent electronic Raman excitation of valley-orbit split states of phosphorus dopants in silicon

In this study, we demonstrate coherent optical excitation of the electronic Raman transition between the $1s\left(A_1\right)$ and $1s\left(E\right)$ split states of phosphorus donor in crystalline silicon. The dynamics of the generated wavepacket is characterized in the time domain using a degenerate pump-probe technique with mid-infrared femtosecond pulses via transient polarization anisotropy of the probe pulse. In addition, we study the role of resonantly excited carriers, and we show that the amplitude and coherence time of the electronic wavepacket depend on the pre-excited carrier density. Further, we demonstrate that under certain conditions, the Raman-type excitation changes to displacive impulsive excitation, which allows us to address the Raman-forbidden transition between $1s\left(A_1\right)$ and $1s\left(T_1\right)$.

cond-mat.mes-hall↗

arXiv2024

Quench switching of Mn2As

We demonstrate that epitaxial thin film antiferromagnet Mn2As exhibits the quench-switching effect, which was previously reported only in crystallographically similar antiferromagnetic CuMnAs thin films. Quench switching in Mn2As shows stronger increase in resistivity, reaching hundreds of percent at 5K, and significantly longer retention time of the metastable high-resistive state before relaxation towards the low-resistive uniform magnetic state. Qualitatively, Mn2As and CuMnAs show analogous parametric dependence of the magnitude and relaxation of the quench-switching signal. Quantitatively, relaxation dynamics in both materials show direct proportionality to the Néel temperature. This confirms that the quench switching has magnetic origin in both materials. The presented results suggest that the antiferromagnets crystalizing in the Cu2Sb structure are well suited for exploring and exploiting the intriguing physics of highly non-uniform magnetic states associated with the quench switching.

cond-mat.mtrl-sci↗

arXiv2022

Anomalous Nernst effect in Mn$_3$NiN thin films

The observation of a sizable anomalous Hall effect in magnetic materials with vanishing magnetization has renewed interest in understanding and engineering this phenomenon. Antiferromagnetic antiperovskites are one of emerging material classes that exhibit a variety of interesting properties owing to a complex electronic band structure and magnetic ordering. Reports on the anomalous Nernst effect and its magnitude in this class of materials are, however, very limited. This scarcity may be partly due to the experimental difficulty of reliably quantifying the anomalous Nernst coefficient. Here, we report experiments on the anomalous Nernst effect in antiferromagnetic antiperovskite Mn$_3$NiN thin films. Measurement of both the anomalous Hall and Nernst effects using the same sample and measurement geometry makes it possible to directly compare these two effects and quantify the anomalous Nernst coefficient and conductivity in Mn$_3$NiN. We carefully evaluate the spatial distribution of the thermal gradient in the sample and use finite element modeling to corroborate our experimental results.

cond-mat.mtrl-sci↗