arXiv subjects

Milorad V. Milosevic

Publications and source records attributed to Milorad V. Milosevic.

At least 19 recordsLinked to original sources

arXiv2026

Binary magnetism and directional magnon transport in alkali-doped CrI$_3$

The recent realization of two-dimensional (2D) magnets, with CrI$_3$ as a pioneering example, has opened new avenues in the fields of 2D materials and magnetism. This breakthrough has been followed by extensive efforts to manipulate and exploit their magnetic properties. In this work, we investigate the adsorption of alkali-metal atoms as a route to control the magnetic behavior of monolayer CrI$_3$. We show that, upon adsorption, alkali-metal atoms donate an electron to the CrI$_3$ layer, leading to the formation of inequivalent Cr sites, with one Cr atom exhibiting an enhanced magnetic moment of $4~μ_B$, while the other retains its typical $3~μ_B$ moment. These modifications significantly alter the magnetic exchange interactions, including the emergence of anisotropic exchange and Dzyaloshinskii--Moriya interactions (DMI). Consequently, the doped systems exhibit non-collinear magnetic ground states, modified temperature-dependent magnetism, and anisotropic spin-wave propagation, with a preferred propagation direction that becomes increasingly pronounced with increasing dopant size. Furthermore, an asymmetry between spin-wave propagation in opposite directions is observed, giving rise to a diode-like effect, particularly for heavier dopants. This behavior is attributed to the enhanced DMI, which breaks the symmetry of the magnon dispersion. These results demonstrate that alkali-metal doping provides an effective route to tune anisotropic and nonreciprocal magnonic properties in two-dimensional magnetic materials.

cond-mat.mtrl-sci↗

arXiv2026

In silico design of magnonic lasing in constricted waveguides

Analogue black-hole systems have been proposed in various physical platforms, including magnetic materials, offering rich physics and promising applications such as wave lasing. However, their practical realization and characterization remain largely unexplored. Here, we present an in silico study of magnonic black-hole phenomena in constricted ferromagnetic waveguides driven by spin-polarized currents. Using micromagnetic simulations with a two-dimensional Poisson solver to obtain realistic current-density profiles, we demonstrate the formation of a double-hole cavity bounded by analogue event horizons, enabling resonant spin-wave amplification. We characterize the resonances as a function of magnetic and geometric parameters and identify the corresponding spin-wave modes. We further show that gradual tapers enhance transmission by suppressing spin-wave reflections, while interfacial Dzyaloshinskii-Moriya interaction can mimic the current-induced Doppler shift, substantially reducing the critical current density required for applications and, consequently, Joule heating. Finally, we demonstrate a spin-wave laser in which thermally excited spin waves undergo selective amplification and coherent emission at well-defined resonance frequencies. These results provide design principles for magnonic analogues of gravitational systems and point toward their potential for advanced spintronic applications.

cond-mat.mes-hall↗

arXiv2026

Excitonic Landscape of Monolayer Transition-Metal Dichalcogenides: Experimental Discrepancies, Theoretical Advances, and Strain Dependence

Excitons in monolayer transition-metal dichalcogenides (TMDs) have garnered significant attention because of their large binding energies due to weakly screened Coulomb interaction, and direct bandgap at the K/K$^\prime$ point in the hexagonal Brillouin zone featuring spin-polarised bands due to spin-orbit coupling and lack of inversion symmetry. This makes them prospective for next-generation optoelectronic and quantum devices. However, despite the intense research activity, the reported values for exciton binding energies, quasiparticle gaps, and spectral features exhibit substantial variation across both experimental and theoretical studies. In this article, we present a comprehensive and critical assessment of the current understanding of excitonic properties in single-layer TMDs, integrating results from the angle-resolved photoemission spectroscopy (ARPES), photoluminescence (PL) measurements, and other experimental techniques with first-principles theoretical insights. Special emphasis is placed on the comparison and reconciliation of discrepancies observed across different experimental setups and sample qualities. Furthermore, we highlight our state-of-the-art GW-BSE calculations, which include both equilibrium and laterally strained systems, to systematically analyse the behaviour of direct and indirect excitons. By evaluating the effect of strain as a tunable control variable, we demonstrate its potential to engineer excitonic properties, supported by cross-validation against prior theoretical predictions and experimental findings. In doing so, we clarify the sources of discrepancies in the literature and offer a unified perspective on excited-state engineering strategies in two-dimensional TMDs.

physics.optics↗

arXiv2026

Harnessing Josephson-Shapiro physics to verify interlayer exciton superfluidity

Obtaining definitive evidence for zero-magnetic-field exciton superfluidity in electron-hole bilayers remains a longstanding challenge because the condensate is electrically neutral and its phase coherence is difficult to probe directly. We propose a direct test based on Shapiro steps in a Dayem-bridge excitonic Josephson junction. We predict clearly resolvable Shapiro plateaus in experimentally accessible current and voltage regimes for double-bilayer graphene and, in the low-density regime, double-layer transition-metal dichalcogenides. Moreover, by tuning the density across the BCS-BEC crossover we show that the Shapiro response acquires a distinct nonmonotonic evolution. This is determined by the nonmonotonic behavior of the healing length in the crossover from bosonic to fermionic excitations. Observation of these signatures would provide direct evidence of exciton superfluidity and establish exciton bilayers as a platform for neutral Josephson devices.

cond-mat.supr-con↗

arXiv2025

Current-Induced Modulation of Spin-Wave Propagation in a Y-Junction via Transverse Spin-Transfer Torque

We report the transverse control of spin-wave propagation in the configuration where the spin-wave wavevector k is perpendicular to the charge-current density J. Building on theoretical predictions of spin-wave refraction by nonuniform spin-polarized currents, and guided by micromagnetic simulations used to optimize the device geometry and current distribution, we experimentally explore a Y-shaped Permalloy structure in which a locally injected current perturbs the spin-wave dispersion. Measurements reveal current-dependent amplitude differences between the two output branches, providing initial experimental indications consistent with transverse, spin-transfer-torque-driven deflection. Although the magnitude of the effect is modest and accompanied by significant uncertainties, the observed trends qualitatively follow expectations from the simulations. These results demonstrate the feasibility of influencing spin-wave routing through local current injection and establish a proof-of-concept basis for current-controlled manipulation of spin-wave propagation in reconfigurable magnonic circuits.

cond-mat.mes-hall↗

arXiv2025

A Gross-Pitaevskii theory for an excitonic incompressible Bose solid

We show that interlayer excitons in double-layer semiconductor heterostructures can form a Bose solid, which is an incompressible supersolid characterized by exactly one boson per lattice site. This exciton Bose solid would be the first realization of an incompressible supersolid, unlike the generally compressible cluster supersolids seen in dipolar quantum gases. Capturing its characteristics and associated emergent phenomena requires extending the Gross-Pitaevskii formalism to include strong two-particle correlations and exclude exciton self-interactions. We develop such a formalism, we apply it across experimentally accessible exciton densities and interlayer separations, and we show that it incorporates both superfluid and incompressible supersolid ground states. This extended framework allows us to determine the superfluid-supersolid transition and explore the low-temperature properties of the exciton supersolid across its complete parameter space.

cond-mat.quant-gas↗

arXiv2025

Vortices in dipolar condensates of interlayer excitons

Recently observed signatures of Bose-Einstein condensation and superfluidity of dipolar excitons have drawn enormous attention to excitonic semiconductor bilayers. In superfluids, stabilization and observation of vortex matter is usually a decisive proof of coherent condensation order. However to date, the vortex behavior in a 2D excitonic system with aligned dipole-like interactions that are long-range and everywhere repulsive has not been addressed. We here provide a theoretical description of the vortex characteristics, interaction, and lattices in a dipolar exciton superfluid, solving the corresponding Gross-Pitaevskii equation, while varying the exciton dipole moments and the exciton density - both tunable in the experiment, by interlayer separation and gating, respectively. We draw particular attention to the appearance of a maximum in the density redistribution around the edge of each vortex, in the phase-space region where the dipole interactions are particularly strong, and where a transition to an incompressible exciton supersolid is expected.

cond-mat.other↗

arXiv2025

State- and momentum-dependent nonlinear Stark effect of interlayer excitons in bilayer WSe$_2$

Interlayer excitons in van der Waals heterostructures offer rich collective phases, prospective optoelectronic applications, and versatile tunability, where control by electronic means is particularly relevant and practical. Here, in the case of bilayer WSe$_2$, we reveal how layer localization of excitons governs their response to an external electric field. Using Many-Body Perturbation Theory, we calculate the exciton dispersion for different stacking symmetries under applied electric field and/or strain, in order to map the landscape of competing low-energy excitons in four distinct finite-momentum valleys. While intralayer excitons are not affected by the electric field, some interlayer ones exhibit a nonlinear Stark shift that becomes linear after a critical threshold. The degree of nonlinearity is a direct measure of the layer hybridization of the electronic subcomponents of the exciton. Our findings explain the peculiar Stark-shift regimes observed in recent experiments, the nature of (anti)symmetric spectral shifts around zero field, and the sensitivity of dipolar excitons to external perturbations, all highly relevant to their further applications in excitonic condensates, optoelectronics devices and quantum emitters.

cond-mat.mes-hall↗

arXiv2024

Theory of a two-dimensional anharmonic piezoelectric crystal resonator

We developed a lattice dynamical theory of an atomically-thin compressional piezoelectric resonator. Acoustic and optical dynamic displacement response functions are derived and account for frequency-dependent electromechanical coupling. The dynamic susceptibilities for the direct and the converse piezoelectric effects are found equal. The mechanical resonant behavior of longitudinal in-plane displacement waves is investigated as a function of the lateral crystal size and of temperature in the classical and in the quantum regime. In the former case the quality factor of the resonator is inversely proportional to temperature and to crystal size. Below a cross-over temperature the quantum zero-point fluctuations become dominant and put an upper limit on the quality factor which is size independent. As experimentally relevant examples, the theory is applied on two-dimensional hexagonal boron nitride and molybdenum disulfide.

cond-mat.mes-hall↗

arXiv2024

Chiral propagation of plasmons due to competing anisotropies in a twisted photonic heterostructure

We demonstrate chiral propagation of plasmon polaritons and show it is more efficient and easier to control than the recently observed chiral shear phonon polaritons. We consider plasmon polaritons created in an anisotropic two-dimensional (2D) material, twisted with respect to an anisotropic substrate, to best exploit the competition between anisotropic electron-electron interactions and the anisotropic electronic structure of the host material. Gate voltage and twist angle are then used for precise control of the chiral plasmon polaritons, overcoming the existing restrictions with chiral phonon polaritons. These findings open up feasible opportunities for efficient and tunable plasmon-based nanophotonics and compact high-performance on-chip optical devices.

cond-mat.mes-hall↗

arXiv2024

Comment on "Coexistence of superconductivity and topological aspects in beryllenes", Materials Today Physics 38, 101257 (2023)

In a recent publication by Li $\textit{et al.}$, two phases of beryllene - $α$ and $β$ - were predicted to be single-gap superconductors with critical temperatures of 9.9 K and 12.6 K respectively. Moreover, the $α$-beryllene was shown to host type-I Dirac fermions with the existence of nontrivial edge states. We observe significantly weaker superconducting properties of both beryllene configurations. We argue that the superconducting gap evolution with temperature, as shown in Figure 5 (b and d) of Li $\textit{et al.}$, exhibits clearly unphysical trends with increasing temperature, leading to significantly overestimated values of the critical temperature and erroneous conclusions concerning the two-gap superconducting nature of $β$-beryllene. On a positive note, we report the value of the gap in the Dirac cone of the topological states of interest that exceeds the temperature range of superconductivity in $α$-beryllene, supporting the coexistence of topological features and superconductivity in this material.

cond-mat.supr-con↗

arXiv2024

Orbital origin of magnetic moment enhancement induced by charge density wave in kagome FeGe

Interactions among various electronic states such as CDW, magnetism, and superconductivity are of high significance in strongly correlated systems. While significant progress has been made in understanding the relationship between CDW and superconductivity, the interplay between CDW and magnetic order remains largely elusive. Kagome lattices, which intertwine nontrivial topology, charge order, and magnetism, offer an ideal platform for such studies. The kagome magnet FeGe, hosting the unique coupling between CDW and magnetism, has recently garnered considerable attention in that respect. Here we reveal the significant role of the orbital coupling effect during the CDW phase transition, highlighting the orbital origin of the magnetic moment enhancement in FeGe. Our X ray absorption experiments and first principles calculations illuminate the temperature dependent behavior of Fe3d_Ge4p orbital hybridization and corroborate its pivotal impact on the magnetic properties of FeGe. These findings introduce an orbital dimension to the correlation between charge and magnetic degrees of freedom, advancing our understanding of the intriguing quantum phases resulting from this interplay.

cond-mat.str-el↗

arXiv2024

Interface-Induced Ferromagnetism in lateral NiBr2 and NiCl2 Heterostructure

Magnetic skyrmions are promising candidates for future information storing and processing devices. There are different routes for stabilizing the skyrmions. Understanding the interplay mechanism between different scenarios of skyrmion formation is one key factor that can reveal new paths for controlling skyrmion phases. Inspired by the flexibility of two-dimensional materials that offer an exciting playground for manipulating spin textures, we conducted \textit{ab initio} simulations and utilized four-state spin framework to determine magnetic parameters of lateral heterostructure formed by NiBr2 and NiCl2 Monolayers. The obtained spin interaction parameters are utilized to determine the skyrmionic phases via Monte Carlo simulation. Monte Carlo simulation results suggest three distinct phase transition mechanisms exist in the present system. Namely, examination of heat capacity versus temperature curve obtained from average anisotropic exchange energy yields a phase transition between paramagnetic and spin-spiral states at $5$K for pristine NiBr2, a paramagnetic-mixed skyrmion state transition occurs at 17 K for pristine NiCl2, and a high-temperature ferromagnetic-paramagnetic transition at T=80 K is observed for the heterostructure region, indicating that some kind of intrinsic ferromagnetism may originate at the interface of pristine Janus structures.

cond-mat.mtrl-sci↗

arXiv2024

Ultrasensitive acoustic graphene plasmons in a graphene-transition metal dichalcogenide heterostructure: strong plasmon-phonon coupling and wavelength sensitivity enhanced by a metal screen

Acoustic plasmons in graphene exhibit strong confinement induced by a proximate metal surface and hybridize with phonons of transition metal dichalcogenides (TMDs) when these materials are combined in a van der Waals heterostructure, thus forming screened graphene plasmon-phonon polaritons (SGPPPs), a type of acoustic mode. While SGPPPs are shown to be very sensitive to the dielectric properties of the environment, enhancing the SGPPPs coupling strength in realistic heterostructures is still challenging. Here we employ the quantum electrostatic heterostructure model, which builds upon the density functional theory calculations for monolayers, to show that the use of a metal as a substrate for graphene-TMD heterostructures (i) vigorously enhances the coupling strength between acoustic plasmons and the TMD phonons, and (ii) markedly improves the sensitivity of the plasmon wavelength on the structural details of the host platform in real space, thus allowing one to use the effect of environmental screening on acoustic plasmons to probe the structure and composition of a van der Waals heterostructure down to the monolayer resolution.

cond-mat.mes-hall↗

arXiv2024

Skyrmion blinking from the conical phase

While the transition between skyrmionic and non-topological states has been widely explored as a bit operation for information transport and storage in spintronic devices, the ultrafast dynamics of such transitions remains challenging to observe and understand. Here, we utilize spin-dynamics simulations and harmonic transition state theory (HTST) to provide an in-depth analysis of the nucleation of skyrmionic states in helimagnets. We reveal a persistent blinking (creation-annihilation) phenomenon of these topological states under specific conditions near the phase boundary between skyrmion and conical states. Through a minimum-energy path analysis, we elucidate that this blinking behavior is favored by the formation of chiral bobber (CB) surface states and that the collapse of CBs differs from that of skyrmions in thin films due to their different oscillation modes. We further employ HTST to estimate the typical blinking time as a function of the applied magnetic field and temperature. Finally, we illustrate the practical use of skyrmion blinking for controlled probabilistic computing, exemplified by a skyrmion-based random-number generator.

cond-mat.mes-hall↗

arXiv2022

Intrinsic control of interlayer exciton generation rate in van der Waals materials via Janus layers

We demonstrate the possibility of engineering the optical properties of transition metal dichalcogenide heterobilayers when one of the constitutive layers has a Janus structure. This has important consequences for the charge separation efficiency. We investigate different MoS$_2$@Janus layer combinations using first-principles methods including electron-hole interactions (excitons) and exciton-phonon coupling. The direction of the intrinsic electric field from the Janus layer modifies the electronic band alignments and, consequently, the energy separation between interlayer exciton states -- which usually have a very low oscillator strength and hence are almost dark in absorption -- and bright in-plane excitons. We find that in-plane lattice vibrations strongly couple the two states, so that exciton-phonon scattering may be a viable generation mechanism for interlayer excitons upon light absorption. In particular, in the case of MoS$_2$@WSSe, the energy separation of the low-lying interlayer exciton from the in-plane exciton is resonant with the transverse optical phonon modes (40 meV). We thus identify this heterobilayer as a prime candidate for efficient electron-hole pair generation with efficient charge carrier separation.

cond-mat.mes-hall↗

arXiv2022

Causes and consequences of ordering and dynamic phases of confined vortex rows in superconducting nanostripes

Understanding the behaviour of vortices under nanoscale confinement in superconducting circuits is of importance for development of superconducting electronics and quantum technologies. Using numerical simulations based on the Ginzburg-Landau theory for non-homogeneous superconductivity in the presence of magnetic fields, we detail how lateral confinement organises vortices in a long superconducting nanostripe, and present a phase diagram of vortex configurations as a function of the stripe width and magnetic field. We discuss why average vortex density is reduced and reveal that confinement also has profound influence on vortex dynamics in the dissipative regime under sourced electrical current, mapping out transitions between asynchronous and synchronous vortex rows crossing the nanostripe as the current is varied. Synchronous crossings are of particular interest, since they cause single-mode modulations in the voltage drop along the stripe in a high (typically GHz-to-THz) frequency range.

cond-mat.supr-con↗

arXiv2022

Superconductivity in functionalized niobium-carbide MXenes

We show the effect of Cl and S functionalization on the superconducting properties of layered (bulk) and monolayer niobium carbide (Nb$_2$C) MXene crystals, based on first-principles calculations combined with Eliashberg theory. For the bulk layered Nb$_2$CCl$_2$, the calculated superconducting transition temperature ($T_c$) is in very good agreement with the recently measured value of 6 K. We show that $T_c$ is enhanced to 10 K for monolayer Nb$_2$CCl$_2$, due to an increase in the density of states at the Fermi level, and the corresponding electron-phonon coupling. We further demonstrate a feasible gate-induced enhancement of $T_c$ up to 40 K for both bulk-layered and monolayer Nb$_2$CCl$_2$ crystals. For the S-functionalized cases our calculations reveal the importance of phonon softening in understanding their superconducting properties. Finally, we predict that Nb$_3$C$_2$S$_2$ in bulk-layered and monolayer form is potentially superconducting, with a $T_c$ around 30 K. Considering that Nb$_2$C is not superconducting in pristine form, our findings promote functionalization as a pathway towards robust superconductivity in MXenes.

cond-mat.supr-con↗