arXiv subjects

Maksym Myronov

Publications and source records attributed to Maksym Myronov.

10 recordsLinked to original sources

arXiv2026

All-Electric Quantum State Transfer via Spin-Orbit Phase Matching

Semiconductor hole-spin qubits offer a promising route to quantum computation due to their weak hyperfine interaction, and strong intrinsic spin-orbit coupling enabling electric control of qubits. Scalable architectures, however, require coherent long-distance quantum state transfer, which is hindered in these systems by spin-orbit induced anisotropic exchange. Here we show that this limitation can be overcome by using an all-electric control protocol. By tuning the electric field strength, we identify discrete spin-orbit phase-matching conditions that restore near-perfect state transfer, independent of the rotation axis. Complementarily, controlling the electric field direction aligns the spin-orbit axis, suppressing excitation non-conserving processes and enabling robust transfer without fine tuning. Our results establish that electrical control of spin-orbit phases through either magnitude tuning or axis alignment as a practical route for robust quantum information transport in hole-spin quantum dot arrays.

quant-ph↗

arXiv2025

Characterization of superconducting germanide and germanosilicide films of Pd, Pt, Rh and Ir formed by solid-phase epitaxy

Facilitated by recent advances in strained Ge/SiGe quantum well (QW) growth technology, superconductor-semiconductor hybrid devices based on group IV materials have been developed, potentially augmenting the functionality of quantum circuits. The formation of highly transparent superconducting platinum germanosilicide (PtSiGe) contacts to Ge/SiGe heterostructures by solid-phase epitaxy between Pt and SiGe has recently been reported, although with a relatively low critical temperature $<1\,\mathrm{K}$. Here, we present a comparative study of the superconducting properties of Pt, Pd, Rh, and Ir germanides, along with an in-depth characterization of Ir(Si)Ge films formed by solid-phase epitaxy. For films fabricated under optimal epitaxy conditions, we report $T_\mathrm{c}=3.4\,\mathrm{K}$ ($2.6\,\mathrm{K}$ for IrGe (IrSiGe). High-resolution scanning transmission electron microscopy (HRSTEM) and energy-dispersive X-ray spectroscopy (EDX) reveal that Ir reacts with Ge substrates to form a polycrystalline IrGe layer with a sharp IrGe/Ge interface.

cond-mat.supr-con↗

arXiv2025

Optical control of the spin-Hall effect in a two-dimensional hole gas

Relativistic effects influence the motion of charged particles in solids by intertwining spin and momentum. The resulting phenomena exhibit rich and intriguing properties that can unveil radically new quantum devices. In this context, the two-dimensional hole gas formed in group IV heterostructures is a particularly promising platform, owning to a notable spin-orbit coupling. However, the exploitation of spin-momentum locking and precise manipulation of spin currents has remained elusive thus far. Here we use the modulation-doping technique to break inversion symmetry at novel Ge1-xSnx/Ge interfaces and explore spin-orbit phenomena in the emergent Rashba-coupled hole gases. Magneto-optical investigations demonstrate the unusual establishment of a staggered band alignment with carrier lifetime in the ns range. Optical spin orientation is then leveraged to directly inject spin-polarized currents in the Rashba-split 2D gas. Spin-to-charge conversion is shown to genuinely occur at the staggered gap through the inverse spin-Hall effect. This provides unprecedented access to low-order contributions of the spin-orbit Hamiltonian. Moreover, it leads to the startling demonstration that the spin Hall angle can be optically controlled by modifying the Rashba coupling through the photoexcitation density. Ge1-xSnx quantum wells thus offer innovative solutions and functionalities stemming from their unique spin-dependent properties and intriguing quantum phenomena at the crossroad between transport and photonic realms.

cond-mat.mes-hall↗

arXiv2020

Magneto-optical determination of the carrier lifetime in coherent Ge(1-x)Sn(x)/Ge heterostructures

We present a magneto-optical study of the carrier dynamics in compressively strained Ge(1-x)Sn(x) films having Sn compositions up to 10% epitaxially grown on blanket Ge on Si (001) virtual substrates. We leverage the Hanle effect under steady-state excitation to study the spin-dependent optical transitions in presence of an external magnetic field. This allowed us to obtain direct access to the dynamics of the optically-induced carrier population. Our approach singled out that at cryogenic temperatures the effective lifetime of the photogenerated carriers in coherent Ge(1-x)Sn(x) occurs in the sub-ns time scale. Supported by a model estimate of the radiative lifetime, our measurements indicate that carrier recombination is dominated by non-radiative processes. Our results thus provide central information to advance the fundamental understanding of carrier kinetics in this novel direct-gap group-IV material system. Such knowledge can be a stepping stone in the quest for the implementation of Ge(1-x)Sn(x)-based functional devices.

physics.optics↗

arXiv2020

The germanium quantum information route

In the worldwide endeavor for disruptive quantum technologies, germanium is emerging as a versatile material to realize devices capable of encoding, processing, or transmitting quantum information. These devices leverage special properties of the germanium valence-band states, commonly known as holes, such as their inherently strong spin-orbit coupling and the ability to host superconducting pairing correlations. In this Review, we initially introduce the physics of holes in low-dimensional germanium structures with key insights from a theoretical perspective. We then examine the material science progress underpinning germanium-based planar heterostructures and nanowires. We review the most significant experimental results demonstrating key building blocks for quantum technology, such as an electrically driven universal quantum gate set with spin qubits in quantum dots and superconductor-semiconductor devices for hybrid quantum systems. We conclude by identifying the most promising prospects toward scalable quantum information processing.

cond-mat.mes-hall↗

arXiv2019

Landau polaritons in highly non-parabolic 2D gases in the ultra-strong coupling regime

We probe ultra-strong light matter coupling between metallic terahertz metasurfaces and Landau-level transitions in high mobility 2D electron and hole gases. We utilize heavy-hole cyclotron resonances in strained Ge and electron cyclotron resonances in InSb quantum wells, both within highly non-parabolic bands, and compare our results to well known parabolic AlGaAs/GaAs quantum well (QW) systems. Tuning the coupling strength of the system by two methods, lithographically and by optical pumping, we observe a novel behavior clearly deviating from the standard Hopfield model previously verified in cavity quantum electrodynamics: an opening of a lower polaritonic gap.

cond-mat.mes-hall↗

arXiv2017

Carrier and Spin Coherent Dynamics in Strained Germanium-Tin Semiconductor on Silicon

Germanium-Tin is emerging as a material exhibiting excellent photonic properties. Here we demonstrate optical initialization and readout of spins in this intriguing group IV semiconductor alloy and report on spin quantum beats between Zeeman-split levels under an external magnetic field. Our optical experiments reveal robust spin orientation in a wide temperature range and a persistent spin lifetime that approaches the ns regime at room temperature. Besides important insights into nonradiative recombination pathways, our findings disclose a rich spin physics in novel epitaxial structures directly grown on a conventional Si substrate. This introduces a viable route towards the synergic enrichment of the group IV semiconductor toolbox with advanced spintronics and photonic capabilities.

cond-mat.mtrl-sci↗

arXiv2017

Bunches of misfit dislocations on the onset of relaxation of Si$_{0.4}$Ge$_{0.6}$/Si(001) epitaxial films revealed by high-resolution x-ray diffraction

The experimental x-ray diffraction patterns of a Si$_{0.4}$Ge$_{0.6}$/Si(001) epitaxial film with a low density of misfit dislocations are modeled by the Monte Carlo method. It is shown that an inhomogeneous distribution of 60$^\circ$ dislocations with dislocations arranged in bunches is needed to explain the experiment correctly. As a result of the dislocation bunching, the positions of the x-ray diffraction peaks do not correspond to the average dislocation density but reveal less than a half of the actual relaxation.

cond-mat.mtrl-sci↗

arXiv2016

Temperature-dependent photoluminescence characteristics of GeSn epitaxial layers

GeSn epitaxial heterostructures are emerging as prominent candidates for the monolithic integration of light sources on Si substrates. Here we propose a judicious explanation for their temperature-dependent photoluminescence (PL) that is based upon the so far disregarded optical activity of dislocations. By working at the onset of plastic relaxation, which occurs whenever the epilayer releases the strain accumulated during growth on the lattice mismatched substrate, we demonstrate that dislocation nucleation can be explicitly seen in the PL data. Notably, our findings point out that a monotonous thermal PL quenching can be observed in coherent films, in spite of the indirect nature of the GeSn bandgap. Our investigation, therefore, contributes to a deeper understanding of the recombination dynamics in this intriguing group IV alloy and offers insights into crucial phenomena shaping the light emission efficiency.

cond-mat.mtrl-sci↗

arXiv2015

An experimental demonstration of room-temperature spin transport in n-type Germanium epilayers

We report the first experimental demonstration of room-temperature spin transport in n-type Ge epilayers grown on a Si(001) substrate. By utilizing spin pumping under ferromagnetic resonance, which inherently endows a spin battery function for semiconductors connected with the ferromagnet, a pure spin current is generated in the n-Ge at room temperature. The pure spin current is detected by using the inverse spin Hall effect of either Pt or Pd electrode on the n-Ge. A theoretical model including a geometrical contribution allows to estimate a spin diffusion length in n-Ge at room temperature to be 660 nm. The temperature dependence of the spin relaxation time provides evidence for Elliott-Yafet spin relaxation mechanism.

cond-mat.mtrl-sci↗