arXiv subjects

Roman Ya. Kezerashvili

Publications and source records attributed to Roman Ya. Kezerashvili.

At least 19 recordsLinked to original sources

arXiv2026

Intervalley Magnetotrions Tunable by Electric and Magnetic Fields in Buckled Two-Dimensional Materials

We develop a theoretical framework for intervalley magnetotrions in buckled two-dimensional materials, including silicene, germanene, and stanene, subjected to perpendicular electric and magnetic fields. Within the effective-mass approximation, the three-particle Schr\"odinger equation is formulated with the Rytova--Keldysh interaction potential and analyzed in the high-magnetic-field regime. We demonstrate that intervalley trions with equal electron and hole effective masses constitute an exceptional case for which the center-of-mass and internal motions separate exactly. The center-of-mass motion is governed by a two-dimensional harmonic-oscillator Hamiltonian, leading to quantized Landau states whose energies form electrically tunable Landau surfaces controlled by the magnetic field and the electric-field dependence of the carrier effective masses. The internal motion is investigated by solving the three-body Schr\"odinger equation within the framework of the hyperspherical harmonics method. Numerical calculations reveal that the trion binding energy increases monotonically with both magnetic and electric fields owing to the combined effects of magnetic confinement and electric-field-induced enhancement of the effective masses. The strongest binding is obtained for silicene, followed by stanene and germanene. The present work provides a unified description of both the collective center-of-mass motion and the internal dynamics of magnetotrions in Xene monolayers, demonstrating that both degrees of freedom can be independently manipulated by external electric and magnetic fields.

cond-mat.mes-hall↗

arXiv2026

Bound Trions in Two-Dimensional Monolayers: A Review

Trions -- Coulomb-bound three-particle excitations composed of two like-charge carriers and one oppositely charged carrier -- are central quasiparticles in two-dimensional semiconductors. Reduced dielectric screening and quantum confinement strongly enhance their binding energies, making them robust and experimentally accessible. This review surveys theoretical and experimental advances in trion physics, emphasizing rigorous few-body approaches and the role of dielectric environment, anisotropy, and external electric and magnetic fields. We analyze computational methods for describing trions in two-dimensional configuration spaces and discuss how reduced dimensionality modifies their structure and stability. Connections to many-body phenomena, including screening, Landau-level mixing, and exciton--polaron crossover, are also highlighted.

cond-mat.mes-hall↗

arXiv2026

Possible Existence of $^3_\phi$H, $^4_\phi$H, $^4_\phi$He, and $^5_\phi$He Nuclei

Motivated by recent HAL QCD simulations of the $\phi N$ interaction in the $^4S_{3/2}$ channel and its modification in the $^2S_{1/2}$ channel, we develop a first-principles few-body framework that embeds these potentials into configuration-space Faddeev--Yakubovsky equations. We predict bound $^4_\phi\mathrm{H}$, $^4_\phi\mathrm{He}$, and $^5_\phi\mathrm{He}$ nuclei by performing calculations for $\phi$-mesic $\phi NNN$ and $\phi NNNN$ systems. Both spin-dependent and spin-independent $\phi N$ interactions are considered, leading to deeply and moderately bound states, respectively. The deeply bound states originate from the strong attraction in the $^2S_{1/2}$ $\phi N$ channel. Coulomb shifts of the binding energies are evaluated. Our findings provide the binding mechanism and demonstrate the importance of short-range $\phi N$ attraction.

nucl-th↗

arXiv2025

Bound States of $\Omega$ Baryons in Light Nuclei

We investigate bound states of light $\Omega_{3x}$-clusters ($x = s, c$), motivated by the $\Omega_{3s}N$ potential recently developed by the HAL QCD collaboration. To regularize this potential, we remove the deeply attractive core at $r < 0.4~\mathrm{fm}$ and parametrize the long-range component ($r > 0.4~\mathrm{fm}$) using a two-range Gaussian form. This procedure preserves the relevant two-body bound state energy while having a negligible effect on the $\Omega_{3s}NN$ and $\Omega_{3s}\Omega_{3s}N$ systems. An effective $\Omega_{3s}\alpha$ potential is then constructed by fitting a two-range Gaussian function to the long-range component of the folding potential, enabling calculations of the bound state energies of the $\Omega_{3s}\alpha$, $\Omega_{3s}\alpha\alpha$, and $\Omega_{3s}\Omega_{3s}\alpha$ systems. The regularization procedure leads to a substantial reduction in bound state energies compared to those obtained with the original potential. We further extend the analysis to $\Omega_{3c}$-cluster systems by introducing an $\Omega_{3c}N$ interaction, derived by comparing the existing $\Omega_{3s}\Omega_{3s}$ and $\Omega_{3c}\Omega_{3c}$ potentials. Our results suggest that several parametrizations predict bound states in $\Omega_{3c}$-containing clusters. Finally, the $\Omega_{3s}\Omega_{3s}$ interaction is described using a contact-like potential approach, motivated by the effective field theory.

nucl-th↗

arXiv2025

Propellantless space exploration

Propellantless propulsion refers to methods of space travel that do not require onboard propellant, instead relying on natural forces or external energy sources. In this paper, I review different approaches that have been explored and discuss the pros and cons of each method for interstellar space exploration. Gravitational assist uses planetary gravity to change a spacecraft's speed and direction without fuel. It is effective but limited to specific alignments. Solar sails harness radiation pressure from sunlight for continuous, fuel-free acceleration. While effective over time, they require large, reflective materials that degrade in space. Speed can be enhanced by thermal desorption triggered by solar radiation. Magnetic sails generate thrust by interacting with the solar wind through superconducting loops that produce a magnetic field. They provide lower acceleration compared to solar sails, and their performance depends on the available power and the variability of solar wind conditions. Electric sails utilize charged tethers to repel solar wind protons, producing gradual acceleration. Their effectiveness depends on the successful deployment of very long, lightweight conductive wires. They can achieve higher acceleration than solar sails, and their performance is influenced by available power and solar wind conditions. Lastly, quantum effects, such as the Casimir force, offer a speculative but intriguing route to propellantless propulsion based on the vacuum energy of space.

physics.pop-ph↗

arXiv2025

On $\Omega_{3c}NN$ and $\Omega_{3c} \Omega_{3c} N$ systems with HAL QCD potentials

This study employs the Faddeev formalism in configuration space to investigate the $\Omega_{3c}NN$ cluster containing a triply charmed Omega baryon ($\Omega_{3c}$). Using the recently reported HAL QCD $S$-wave $\Omega_{3c}N$ potentials in the $^3S_1$ and $^5S_2$ channels, together with the MT-I--III nucleon--nucleon potential and neglecting the Coulomb force, we find no bound state for the $\Omega_{3c}np$ system. We predict near-threshold resonances in the $J^{\pi}=5/2^{+}$ (maximal total spin) and $J^{\pi}=1/2^{+}$ (minimal total spin) states, with resonance energies of $1.1~\mathrm{MeV}$ below and $0.0~\mathrm{MeV}$ at the three-body breakup threshold, respectively, at Euclidean time $t/a = 16$. A similar analysis of the $\Omega_{3c}\Omega_{3c}N$ system likewise reveals no bound states, though a possible resonance is indicated. The short-distance behavior of the HAL QCD $\Omega_{3c}N$ potential is also discussed.

nucl-th↗

arXiv2025

Feasibility study of a mission to Sedna -- Nuclear propulsion and advanced solar sailing concepts

Exploring the outer reaches of the Solar System presents significant propulsion and mission design challenges. This study assesses the feasibility of a mission to Sedna using two advanced propulsion concepts: the Direct Fusion Drive (DFD) rocket engine, based on D-$^{3}$He thermonuclear fusion, and a solar sail utilizing thermal desorption of its coating for propulsion. Both are evaluated for a one-way Earth-to-Sedna mission; however, due to the different performances the DFD would enable orbit insertion, whereas for the solar sail a flyby is envisioned. The analysis evaluates key mission parameters, including delivered payload capacity, travel time, and potential science return. For the DFD, we assume a 1.6 MW system with constant thrust and specific impulse, while for the solar sail, we consider acceleration via thermal desorption and a gravity-assist maneuver around Jupiter. The mission analysis incorporates four key phases: departure, interplanetary acceleration, interplanetary coasting, and rendezvous. Sedna is expected to pass through the perihelion of its orbit in 2075--2076 and then move again away from the Sun. Considering the distances involved, a mission targeting the object would need to be launched "relatively" soon, especially if using conventional propulsion systems, which could require up to 30 years of deep-space travel. In our study, results indicate that the DFD could reach Sedna in approximately 10 years, with 1.5 years of thrusting, while the solar sail, assisted by Jupiter's gravity, could complete the journey in 7 years. The feasibility of science payload accommodation, power availability, and communication constraints is also considered. These findings provide a comparative foundation for future deep-space mission planning.

astro-ph.IM↗

arXiv2025

Electric field tunable magnetoexcitons in Xenes-hBN-TMDC, Xenes-hBN-BP, and Xenes-hBN-TMTC heterostructures

In this work, we propose novel van der Waals (vdW) heterostructures composed of Xenes, transition metal dichalcogenides (TMDCs), phosphorene, and transition metal trichalcogenides (TMTCs), which are separated by insulating hexagonal boron nitride (hBN) layers. We investigate theoretically the behavior of Rydberg indirect excitons in Xenes-hBN-TMDC, Xenes-hBN-BP, and Xenes-hBN-TMTC heterostructures, subject to parallel external electric and magnetic fields that are oriented perpendicular to the layers. By incorporating both isotropic and anisotropic materials, we demonstrate that excitonic properties can be effectively tuned through the external field strengths and the heterostructure design. Our results show that the exciton reduced mass and the binding energy increase with the electric field strength, while enhanced dielectric screening from additional hBN layers reduces the binding energy. Anisotropic materials exhibit distinct excitonic responses, including variations in diamagnetic behavior. Moreover, the diamagnetic energy contributions and coefficients decrease with stronger electric fields but increase with the number of hBN layers. Finally, we explore the potential of time-periodic electric fields with Floquet band-structure engineering. These findings provide a comprehensive framework for controlling excitonic phenomena in low-dimensional materials, enabling the design of advanced optoelectronic and quantum devices.

cond-mat.mes-hall↗

arXiv2024

Edge modes in chiral electron double layers

We study the quasiparticles in chiral double layers with electron pairing within the framework of the Bogoliubov de Gennes equation. In the presence of an edge it is demonstrated that the quasiparticle modes can be distinguished as edge modes and bulk modes, which appear at different energies. The bulk-edge correspondence is obtained by an analytic continuation from the in-gap edge modes to the bands of bulk modes. By varying the energy we find a transition from localized edge modes to delocalized bulk modes. We calculate the quasiparticle currents, discuss briefly how these currents couple to external currents, and predict how this can be used to control the quasiparticle modes.

cond-mat.supr-con↗

arXiv2024

Recent advances in space sailing missions and technology: review of the 6th International Symposium on Space Sailing (ISSS 2023)

The 6th International Symposium on Space Sailing (ISSS 2023) took place on June 5-9, 2023 at the New York City College of Technology, the City University of New York. Since its inauguration in Herrsching (Germany, 2007), the ISSS has been held in New York (USA, 2010), Glasgow (UK, 2013), Kyoto (Japan, 2017) and Aachen (Germany, 2019). During the five-day symposium, participants from 14 countries gathered to discuss recent advances in space sailing, investigating new concepts and designs, describing innovative hardware and enabling technologies, strategies for dynamics and control, and providing updates on testing results for systems under development and future mission applications. As part of the 18 sessions, almost 50 oral presentations were held and, subsequently, 17 papers were submitted for review and publication. This paper aims to give an overview of all the cutting-edge technologies, detailed analysis and promising results shared with the scientific community as part of the event. Following the noteworthy deployment of the world's first solar sail IKAROS in 2010, missions like NanoSail-D2 (2011) and LightSail-2 (2019) have showcased the potential of solar sailing technology through successful demonstrations. Besides highlighting advancements in present and future programs, the symposium was an opportunity to reflect on objectives, design and test results from research centers and universities, as well as illustrate applications for interstellar travel, evaluate degrading performance and suggest alternative solutions for known limitations. The following Symposium is scheduled for early summer 2025 and will be hosted by TU Delft.

physics.space-ph↗

arXiv2024

Folding procedure for $\Omega$-$\alpha$ potential

Using the folding procedure, we investigate the bound state of the $\Omega$+$\alpha$ system based on $\Omega$-$N$ ($^{5}S_{2}$) HAL QCD potential. Previous theoretical analyses have indicated the existence of a deeply bound ground state, which is attributed to the strong $\Omega$-nucleon interaction. By employing well-established parameterizations of nucleon density within the alpha particle, and the central HAL QCD $\Omega$-$N$ potential, we performed numerical calculations for the folding $\Omega$-$\alpha$ potential. Our results show that the $V_{\Omega\alpha}(r)$ potential can be accurately fitted using a Woods-Saxon function, with a phenomenological parameter $R = 1.1A^{1/3} \approx 1.74$ fm ($A=4$) in the asymptotic region where $2 < r < 3$ fm. We provide a thorough description of the corresponding numerical procedure. Our evaluation of the binding energy of the $\Omega$+$\alpha$ system within the cluster model is consistent with both previous and recent reported findings. To further validate the folding procedure, we also calculated the $\Xi$-$\alpha$ folding potential based on a simulation of the ESC08c $Y$-$N$ Nijmegen model. A comprehensive comparison between the $\Xi$-$\alpha$ folding and $\Xi$-$ \alpha$ phenomenological potentials is presented and discussed.

nucl-th↗

arXiv2024

Bound states of $^{9}_{\phi}$Be and $^{6}_{\phi\phi}$He nuclei with $\phi$+$\alpha$+$\alpha$ and $\phi$+$\phi$+$\alpha$ cluster models

We investigate the $^{9}_{\phi}$Be and $^{6}_{\phi\phi}$He $\phi$ mesic nuclei within the framework of the three-body cluster model as the $\phi$+$\alpha$+$\alpha$ and $\phi$+$\phi$+$\alpha$ systems, using the Faddeev formalism in configuration space. The $\phi$-$\alpha$ potential is determined through a folding procedure of the HAL QCD $\phi$-$N$ interaction in the $^4S_{3/2}$ channel with the matter distribution of $^4$He. The phenomenological $\alpha$-$\alpha$ and $\phi$-$\phi$ potentials are taken from the literature. Additionally, we construct a Wood-Saxon (WS) type interaction to simulate the $\phi$-$\alpha$ potential, also taken from the literature, based on an effective Lagrangian approach that includes $K\bar{K}$ meson loops in the $\phi$-meson self-energy. A comparison of binding energies obtained for both types of the $\phi$-$\alpha$ interactions reveals qualitative agreement. %between the obtained approaches. We predict the binding energy for the $^{9}_{\phi}$Be and $^{6}_{\phi\phi}$He $\phi$ mesic nuclei as the mirror $\phi$+$\alpha$+$\alpha$ and $\phi$+$\phi$+$\alpha$ systems in the range of 1-11 MeV and 3-10 MeV, respectively. The range of values of the binding energies relies on the choice of the WS $\phi$-$\alpha$ interaction parameters.

nucl-th↗

arXiv2024

On a possible $^{3}_{\phi}$H hypernucleus with HAL QCD interaction

Within the framework of the Faddeev formalism in configuration space, we investigate bound states in the $\phi NN$ system with total isospin $T=0$ and $T=1$. The recently proposed lattice HAL QCD $\phi N$ potential in the $^{4}S_{3/2}$ channel does not support either $\phi N$ or $\phi NN$ bound states. The HAL QCD $\phi N$ potential in the $^{2}S_{1/2}$ channel suggests the bound states for $\phi N$ and $\phi NN (S=0)$ systems. However, the binding energies are highly sensitive to variations of the enhancement factor $\beta$, and the $\phi NN$ system is extremely strongly bound in the state $S=0$. Considering a spin-averaged potential %$(\frac{1}{3}V_{\phi N}^{1/2}+\frac{2}{3}V_{\phi N}^{3/2})$ for the state $S=1$ yields a bound state for $^3_\phi$H $(S=1)$ hypernucleus with the binding energy (BE) 14.9 MeV when $\beta = 6.9$. The evaluation of the BE for the $S=1$, $T=1$ three-body state results in 5.47 MeV. %Also, We evaluated the BE for the $S=1$, $T=1$ three-body state as 5.47 MeV. Additionally, calculations using our approach confirm the bound states for the $\phi NN$ ($S=2,T=0$ and $S=1, T=1$) system previously predicted with the Yukawa-type potential motivated by the QCD van der Waals attractive force, mediated by multi-gluon exchanges.

nucl-th↗

arXiv2024

Electric-field-tuned binding energies of trions in silicene, germanene, and stanene monolayers

We predict the formation of intravalley controllable trions in buckled two-dimensional (2D) materials such as silicene, germanene, and stanene monolayers in an external electric field. Performing a study within the framework of a nonrelativistic potential model using the method of hyperspherical harmonics (HH), the three-body Schr\"{o}dinger equation is solved with the Rytova-Keldysh potential by expanding the wave functions of a trion in terms of the HH. Then, we numerically solve a resultant system of coupled differential equations. The ground state energies of intravalley trions controlled by the external electric field are presented. The dependencies of the binding energy (BE) of trions in silicene, germanene, and stanene as a function of the electric field are shown to be qualitatively similar. BEs of trions formed by $A$ and $B$ excitons have a non-negligible difference that increases slightly as the electric field increases. We demonstrate that trion BEs can be controlled by the external electric field.

cond-mat.mes-hall↗

arXiv2023

Bound state solutions of the two--dimensional Schr\"{o}dinger equation with Kratzer--type potentials

Exactly solvable models play an extremely important role in many fields of quantum physics. In this study, the Schr\"{o}dinger equation is applied for a solution of a two--dimensional (2D) problem for two particles interacting via Kratzer, and modified Kratzer potentials. We found the exact bound state solutions of the two--dimensional Schr\"{o}dinger equation with Kratzer--type potentials and present analytical expressions for the eigenvalues and eigenfunctions. The eigenfunctions are given in terms of the associated Laguerre polynomials.

quant-ph↗

arXiv2023

Trions in two-dimensional monolayers within the hyperspherical harmonics method. Application to transition metal dichalcogenides

We develop the theoretical formalism and study the formation of valley trions in transition metal dichalcogenide (TMDC) monolayers within the framework of a nonrelativistic potential model using the method of hyperspherical harmonics (HH) in four-dimensional space. We present the solution of the three-body Schr\"{o}dinger equation with the Rytova-Keldysh (RK) potential by expanding the wave function of a trion in terms of the HH. The antisymmetrization of trions wave function is based on the electron and hole spin and valley indices. We consider a long-range approximation when the RK potential is approximated by the Coulomb potential and a short-range limit when this potential is approximated by the logarithmic potential. In a diagonal approximation, the coupled system of differential equations for the hyperradial functions is decoupled in both limits. Our approach yields the analytical solution for binding energy and wave function of trions in the diagonal approximation for these two limiting cases: the Coulomb and logarithmic potentials. We obtain exact analytical expressions for eigenvalues and eigenfunctions for negatively and positively charged trions. The corresponding energy eigenvalues can be considered as the lower and upper limits for the trions binding energies. The proposed theoretical approach can describe trions in TMDCs and address the energy difference between the binding energies of $X^{-}$ and $X^{+}$ in TMDC. Results of numerical calculations for the ground state energies with the RK potential are in good agreement with similar calculations and in reasonable agreement with experimental measurements of trion binding energies.

cond-mat.mes-hall↗

arXiv2023

The charge and mass symmetry breaking in the $KK\bar{K}$ system

In the framework of the Faddeev equations in configuration space, we investigate the $K$(1460) meson as a resonant state of the $KK\bar{K}$ kaonic system. We perform calculations for the particle configurations $K^{0}K^{+}K^{-}$ and $K^{0}K^{+}\overline{{K}^{0}}$ within two models: the $ABC $ model, in which all three particles are distinguishable, and the $AAC$ model when two particles are identical. The models differ in their treatment of the kaon mass difference and the attractive Coulomb force between the $K^{+}K^{-}$ pair. We found that the Coulomb shift adds over 1 MeV to the three-body binding energy. The expected correction to the binding energy due to mass redistribution from $AA$ to $AB$ is found to be negligible, up to a maximum of 6\% of the relative mass correction. At the same time, the symmetry of the wave function is distorted depending on the mass ratio value. We found that the repulsive $KK$ interaction plays essential role in the binding energy of the $KK\bar K$ system and report the mass of 1461.8 or 1464.1 MeV for the neutral $K^{0}$(1460) and 1466.5 or 1468.8 MeV for the charged $K^{+}$(1460) resonances, respectively, depending on the parameter sets for $KK$ and $K\bar{K}$ interactions.

nucl-th↗

arXiv2022

On superfluidity of indirect excitons in transition metals trichalcogenides van der Waals heterostructures

We predict angle-dependent superfluidity for a new class of 2D materials -- transition metals trichalcogenides (TMTC). Within a mean-field approach superfluidity of indirect excitons in TMTC van der Waals heterostructures (vdWHs) is studied. We use different potentials for charged carriers interaction to analyze the influence of the screening on the studied phenomena. Our study demonstrates the angle-dependent superfluidity temperature in TMTC vdWHs: for a given density a maximum and minimum $T_c$ of superfluidity occurs along chain and $a$-directions, respectively. This work can guide experimental research toward the realization of anisotropic superfluidity in TMTC vdWH. We suggest an experiment for the observation of anisotropic superfluidity in TMTC vdWH.

cond-mat.mes-hall↗