arXiv subjects

M. V. Milošević

Publications and source records attributed to M. V. Milošević.

At least 19 recordsLinked to original sources

arXiv2026

Symmetry-Tunable Skyrmions and Merons in Magnetic Nanodisks via Spatially Engineered Anisotropy

We demonstrate that spatially engineered magnetic anisotropy can stabilize skyrmion and meron spin textures in magnetic nanodisks even in the absence of Dzyaloshinskii-Moriya interaction (DMI). Using a constrained analytical model and micromagnetic simulations, we show that competing perpendicular and in-plane anisotropies can generate non-collinear topological textures in non-chiral magnetic systems. We further show that DMI and dipolar interactions lift the helicity degeneracy and select preferred chiral configurations; micromagnetic simulations were used to identify physically stable states. These results establish anisotropy-patterned nanodisks as a platform for studying DMI-free topological spin textures and their controllable magnetic response. We also show that arrays of anisotropy-engineered skyrmions can control spin-wave transmission by manipulating their vorticity arrangement, pointing to reconfigurable magnonic elements based on non-chiral topological textures.

cond-mat.mes-hall↗

arXiv2025

Tuning of exciton type by environmental screening

We theoretically investigate the binding energy and electron-hole (e-h) overlap of excitonic states confined at the interface between two-dimensional materials with type-II band alignment, i.e., with lowest conduction and highest valence band edges placed in different materials, arranged in a side-by-side planar heterostructure. We propose a variational procedure within the effective mass approximation to calculate the exciton ground state and apply our model to a monolayer MoS$_2$/WS$_2$ heterostructure. The role of nonabrupt interfaces between the materials is accounted for in our model by assuming a W$_x$Mo$_{1-x}$S$_2$ alloy around the interfacial region. Our results demonstrate that (i) interface-bound excitons are energetically favorable only for small interface thickness and/or for systems under high dielectric screening by the materials surrounding the monolayer, and that (ii) the interface exciton binding energy and its e-h overlap are controllable by the interface width and dielectric environment.

cond-mat.mes-hall↗

arXiv2025

Many-body skyrmion interactions in helimagnets

Many-body interactions strongly influence the structure, stability, and dynamics of condensed-matter systems, from atomic lattices to interacting quasi-particles such as superconducting vortices. Here, we investigate theoretically the pairwise and many-body interaction terms among skyrmions in helimagnets, considering both the ferromagnetic and conical spin backgrounds. Using micromagnetic simulations, we separate the exchange, Dzyaloshinskii-Moriya, and Zeeman contributions to the skyrmion-skyrmion pair potential, and show that the binding energy of skyrmions within the conical phase depends strongly on the film thickness. For small skyrmion clusters in the conical phase, three-body interactions make a substantial contribution to the cohesive energy, comparable to that of pairwise terms, while four-body terms become relevant only at small magnetic fields. As the system approaches the ferromagnetic phase, these higher-order contributions vanish, and the interactions become essentially pairwise. Our results indicate that realistic models of skyrmion interactions in helimagnets in the conical phase must incorporate many-body terms to accurately capture the behavior of skyrmion crystals and guide strategies for controlling skyrmion phases and dynamics.

cond-mat.mes-hall↗

arXiv2025

Striped excitonic (super)solid in anisotropic semiconductors with screened exciton interactions

Within the Gross-Pitaevskii framework, we reveal the emergence of a crystallized phase of an exciton condensate in an atomically-thin anisotropic semiconductor, where screening of exciton-exciton interactions is introduced by a proximal doped graphene layer. While such screened interactions are expected to yield a hexagonal crystal lattice in the excitonic condensate in isotropic semiconductor quantum wells [see e.g. Phys. Rev. Lett. \textbf{108}, 060401 (2012)], here we show that for atomically thin semiconductors with strong electronic anisotropy, such as few-layer black phosphorus, the crystallized exciton phase acquires a parallel stripe structure - unanticipated to date. The optimal conditions for the emergence of this phase, as well as for its coexistence with excitonic superfluidity in a striped supersolid phase, are identified.

cond-mat.mes-hall↗

arXiv2024

Magneto-optical conductivity of monolayer transition metal dichalcogenides in the presence of proximity-induced exchange interaction and external electrical field

We theoretically investigate the magneto-optical (MO) properties of monolayer (ML) transition metal dichalcogenides (TMDs) in the presence of external electrical and quantizing magnetic fields and of the proximity-induced exchange interaction. The corresponding Landau Level (LL) structure is studied by solving the Schrödinger equation and the spin polarization in ML-TMDs under the action of the magnetic field is evaluated.The impact of trigonal warping on LLs and MO absorption is examined. Furthermore, the longitudinal MO conductivity is calculated through the dynamical dielectric function under the standard random-phase approximation (RPA) with the Kubo formula. We take ML-MoS$_2$ as an example to examine the effects of proximity-induced exchange interaction, external electrical and magnetic fields on the MO conductivity induced via intra- and interband electronic transitions among the LLs. For intraband electronic transitions within the conduction or valence bands, we can observe two absorption peaks in terahertz (THz) frequency range. While the interband electronic transitions between conduction and valence LLs show a series of absorption peaks in the visible range. We find that the proximity-induced exchange interaction, the carrier density, the strengths of the external electrical and magnetic fields can effectively modulate the positions of the absorption peaks and the shapes of the MO absorption spectra. The results obtained from this study can benefit to an in-depth understanding of the MO properties of ML-TMDs which can be potentially applied for magneto-optic, spintronic and valleytronic devices working in visible to THz frequency bandwidths.

cond-mat.mes-hall↗

arXiv2024

Longitudinal and transverse mobilities of $n$-type monolayer transition metal dichalcogenides in the presence of proximity-induced interactions at low temperature

We present a detailed theoretical investigation on the electronic transport properties of $n$-type monolayer (ML) transition metal dichalcogenides (TMDs) at low temperature in the presence of proximity-induced interactions such as Rashba spin-orbit coupling (RSOC) and the exchange interaction. The electronic band structure is calculated by solving the Schrödinger equation with a $\mathbf{k}\cdot\mathbf{p}$ Hamiltonian, and the electric screening induced by electron-electron interaction is evaluated under a standard random phase approximation approach. In particular, the longitudinal and transverse or Hall mobilities are calculated by using a momentum-balance equation derived from a semi-classical Boltzmann equation, where the electron-impurity interaction is considered as the principal scattering center at low temperature. The obtained results show that the RSOC can induce the in-plane spin components for spin-split subbands in different valleys, while the exchange interaction can lift the energy degeneracy for electrons in different valleys. The opposite signs of Berry curvatures in the two valleys would introduce opposite directions of Lorentz force on valley electrons. As a result, the transverse currents from nondegenerate valleys can no longer be canceled out so that the transverse current or Hall mobility can be observed. Interestingly, we find that at a fixed effective Zeeman field, the lowest spin-split conduction subband in ML-TMDs can be tuned from one in the $K'$-valley to one in the $K$-valley by varying the Rashba parameter. The occupation of electrons in different valleys also varies with changing carrier density. Therefore, we can change the magnitude and direction of the Hall current by varying the Rashba parameter, effective Zeeman field, and carrier density by, e.g., the presence of a ferromagnetic substrate and/or applying a gate voltage.

cond-mat.mes-hall↗

arXiv2023

Competition of disorder and electron-phonon coupling in 2H-TaSe$_{2-x}$S$_x$ ($0\le x\le 2$) as evidenced by Raman spectroscopy

The vibrational properties of 2H-TaSe$_{2-x}$S$_x$ ($0 \le x \le 2$) single crystals were probed using Raman spectroscopy and density functional theory calculations. The end members revealed two out of four symmetry-predicted Raman active modes, together with the pronounced two-phonon structure, attributable to the enhanced electron-phonon coupling. Additional peaks become observable due to crystallographic disorder for the doped samples. The evolution of the E$_{2g}^2$ mode Fano parameter reveals that the disorder has weak impact on electron-phonon coupling, which is also supported by the persistence of two-phonon structure in doped samples. As such, this research provides thorough insights into the lattice properties, the effects of crystallographic disorder on Raman spectra, and the interplay of this disorder with the electron-phonon coupling in 2H-TaSe$_{2-x}$S$_x$ compounds.

cond-mat.mtrl-sci↗

arXiv2023

Goodenough-Kanamori-Anderson high-temperature ferromagnetism in tetragonal transition-metal xenes

Seminal Goodenough-Kanamori-Anderson (GKA) rules provide the inceptive understanding of the superexchange interaction of two magnetic metal ions bridged with an anion, and suggest fostered ferromagnetic interaction for orthogonal bridging bonds. However, there are no examples of two-dimensional (2D) materials with structure that optimizes the GKA arguments towards enhanced ferromagnetism and its critical temperature. Here we reveal that an ideally planar GKA ferromagnetism is indeed stable in selected tetragonal transition-metal xenes (tTMXs), with Curie temperature above 300~K found in CrC and MnC. We provide the general orbitally-resolved analysis of magnetic interactions that supports the claims and sheds light at the mechanisms dominating the magnetic exchange process in these structures. With recent advent of epitaxially-grown tetragonal 2D materials, our findings earmark tTMXs for facilitated spintronic and magnonic applications, or as a desirable magnetic constituent of functional 2D heterostructures.

cond-mat.mes-hall↗

arXiv2023

On the coupling of magnetic moments to superconducting quantum interference devices

We investigate the coupling factor $ϕ_μ$ that quantifies the magnetic flux $Φ$ per magnetic moment $μ$ of a point-like magnetic dipole that couples to a superconducting quantum interference device (SQUID). Representing the dipole by a current-carrying loop, the reciprocity of mutual inductances of SQUID and loop provides a way of calculating $ϕ_μ(\vec{r}, \vec{e}_μ)$ vs.~position $\vec{r}$ and orientation $\vec{e}_μ$ of the dipole anywhere in space from the magnetic field $B(\vec{r})$ produced by a supercurrent circulating in the SQUID loop. We use numerical simulations based on London and Ginzburg-Landau theory to calculate $ϕ_μ$ from the supercurrent density distributions in various SQUID geometries. We treat the far-field regime ($r\gtrsim a=$ inner size of the SQUID loop) with the dipole placed on the symmetry axis of circular or square shaped loops. We compare expressions for $ϕ_μ$ from filamentary loop models with simulation results for loops with finite width $w$ (outer size $A>a$), thickness $d$ and London penetration depth $λ_L$ and show that for thin ($d\ll a$) and narrow ($w < a$) loops the introduction of an effective loop size $a_{\rm eff}$ in the filamentary loop-model expressions results in agreement with simulations. For a dipole placed in the center of the loop, simulations provide an expression $ϕ_μ(a,A,d,λ_L)$ that covers a wide parameter range. In the near-field regime (dipole centered at small distance $z$ above one SQUID arm) only coupling to a single strip representing the SQUID arm has to be considered. Here, we compare simulations with an analytical expression derived for a homogeneous current density distribution, which yields excellent agreement for $λ_L>w,d$. Moreover, we analyze $ϕ_μ$ provided by the introduction of a constriction in the SQUID arm below the magnetic dipole.

cond-mat.supr-con↗

arXiv2022

Orbital hybridization-driven charge density wave transition in CsV3Sb5 kagome superconductor

Owing to its inherent non-trivial geometry, the unique structural motif of the recently discovered Kagome topological superconductor AV3Sb5 is an ideal host of diverse topologically non-trivial phenomena, including giant anomalous Hall conductivity, topological charge order, charge density wave, and unconventional superconductivity. Despite possessing a normal-state CDW order in the form of topological chiral charge order and diverse superconducting gaps structures, it remains unclear how fundamental atomic-level properties and many-body effects including Fermi surface nesting, electron-phonon coupling, and orbital hybridization contribute to these symmetry-breaking phenomena. Here, we report the direct participation of the V3d-Sb5p orbital hybridization in mediating the CDW phase transition in CsV3Sb5. The combination of temperature-dependent X-ray absorption and first principles studies clearly indicate the Inverse Star of David structure as the preferred reconstruction in the low-temperature CDW phase. Our results highlight the critical role that Sb orbitals plays and establish orbital hybridization as the direct mediator of the CDW states and structural transition dynamics in Kagome unconventional superconductors. This is a significant step towards the fundamental understanding and control of the emerging correlated phases from the Kagome lattice through the orbital interactions and provide promising approaches to novel regimes in unconventional orders and topology.

cond-mat.supr-con↗

arXiv2022

Field-free superconducting diode in a magnetically nanostructured superconductor

A strong superconducting diode effect (SDE) is revealed in a thin superconducting film periodically nanostructured with magnetic dots. The SDE is caused by the current-activated dissipation mitigated by vortex-antivortex pairs (VAPs), which periodically nucleate under the dots, move and annihilate in the superconductor - eventually driving the system to the high-resistive state. Inversing the polarity of the applied current destimulates the nucleation of VAPs, the system remains superconducting up to far larger currents, leading to the pronounced diodic response. Our dissipative Ginzburg-Landau simulations detail the involved processes, and provide reliable geometric and parametric ranges for the experimental realization of such a non-volatile superconducting diode, which operates in absence of any applied magnetic field while being fluxonic by design.

cond-mat.supr-con↗

arXiv2022

Distinctive g-factor of moire-confined excitons in van der Waals heterostructures

We investigated experimentally the valley Zeeman splitting of excitonic peaks in the photoluminescence (PL) spectra of high-quality hBN/WS2/MoSe2/hBN heterostructures at near-zero twist angles under perpendicular magnetic fields up to 20 T. We identify two neutral exciton peaks in the PL spectra: the lower energy one exhibits a reduced g-factor relative to that of the higher energy peak, and much lower than the recently reported values for interlayer excitons in other van der Waals (vdW) heterostructures. We provide evidence that such a discernible g-factor stems from the spatial confinement of the exciton in the potential landscape created by the moire pattern, due tolattice mismatch and/or inter-layer twist in heterobilayers. This renders magneto-PL an important tool to reach deeper understanding of the effect of moire patterns on excitonic confinement in vdW heterostructures.

cond-mat.mes-hall↗

arXiv2021

Zitterbewegung of moiré excitons in twisted MoS$_2$/WSe$_2$ hetero-bilayers

The moiré pattern observed in stacked non-commensurate crystal lattices, such as hetero-bilayers of transition metal dichalcogenides, produces a periodic modulation of their bandgap. Excitons subjected to this potential landscape exhibit a band structure that gives rise to a quasi-particle dubbed moiré exciton. In the case of MoS$_2$/WSe$_2$ hetero-bilayers, the moiré trapping potential has honeycomb symmetry and, consequently, the moiré exciton band structure is the same as that of a Dirac-Weyl fermion, whose mass can be further tuned down to zero with a perpendicularly applied field. Here we show that, analogously to other Dirac-like particles, moiré exciton exhibits a trembling motion, also known as zitterbewegung, whose long timescales are compatible with current experimental techniques for exciton dynamics. This promotes the study of the dynamics of moiré excitons in van der Waals heterostructures as an advantageous solid-state platform to probe zitterbewegung, broadly tunable by gating and inter-layer twist angle.

cond-mat.other↗

arXiv2021

Skyrmion-(Anti)Vortex Coupling in a Chiral Magnet-Superconductor Heterostructure

We report experimental coupling of chiral magnetism and superconductivity in [IrFeCoPt]/Nb heterostructures. The stray field of skyrmions with radius ~50nm is sufficient to nucleate antivortices in a 25nm Nb film, with unique signatures in the magnetization, critical current and flux dynamics, corroborated via simulations. We also detect a thermally-tunable Rashba-Edelstein exchange coupling in the isolated skyrmion phase. This realization of a strongly interacting skyrmion-(anti)vortex system opens a path towards controllable topological hybrid materials, unattainable to date.

cond-mat.supr-con↗

arXiv2021

Probing charge density wave phases and the Mott transition in $1T$-TaS$_2$ by inelastic light scattering

We present a polarization-resolved, high-resolution Raman scattering study of the three consecutive charge density wave (CDW) regimes in $1T$-TaS$_2$ single crystals, supported by \textit{ab initio} calculations. Our analysis of the spectra within the low-temperature commensurate (C-CDW) regime shows $\mathrm{P3}$ symmetry of the system, thus excluding the previously proposed triclinic stacking of the "star-of-David" structure, and promoting trigonal or hexagonal stacking instead. The spectra of the high-temperature incommensurate (IC-CDW) phase directly project the phonon density of states due to the breaking of the translational invariance, supplemented by sizeable electron-phonon coupling. Between 200 and 352\,K, our Raman spectra show contributions from both the IC-CDW and the C-CDW phase, indicating their coexistence in the so-called nearly-commensurate (NC-CDW) phase. The temperature-dependence of the symmetry-resolved Raman conductivity indicates the stepwise reduction of the density of states in the CDW phases, followed by a Mott transition within the C-CDW phase. We determine the size of the Mott gap to be $Ω_{\rm gap}\approx 170-190$ meV, and track its temperature dependence.

cond-mat.str-el↗

arXiv2021

Distinctive magnetic properties of CrI3 and CrBr3 monolayers caused by spin-orbit coupling

After the discovery of magnetism in monolayer CrI3, the magnetic properties of different 2D materials from the chromium-trihalide family are intuitively assumed to be similar, yielding magnetic anisotropy from the spin-orbit coupling on halide ligands. Here we reveal significant differences between the CrI3 and CrBr3 magnetic monolayers in their magnetic anisotropy, resulting Curie temperature, hysteresis in external magnetic field, and evolution of magnetism with strain, all predominantly attributed to distinctly different interplay of atomic contributions to spin-orbit coupling in two materials.

cond-mat.mes-hall↗

arXiv2021

Reversible ratchet effects in a narrow superconducting ring

We study the ratchet effect in a narrow pinning-free superconductive ring based on time-dependent Ginzburg-Landau (TDGL) equations. Voltage responses to external dc an ac currents at various magnetic fields are studied. Due to asymmetric barriers for flux penetration and flux exit in the ring-shaped superconductor, the critical current above which the flux-flow state is reached, as well as the critical current for the transition to the normal state, are different for the two directions of applied current. These effects cooperatively cause ratchet signal reversal at high magnetic fields, which has not been reported to date in a pinning-free system. The ratchet signal found here is larger than those induced by asymmetric pinning potentials. Our results also demonstrate the feasibility of using mesoscopic superconductors to employ superconducting diode effect in versatile superconducting devices.

cond-mat.supr-con↗

arXiv2020

Wave-packet scattering at a normal-superconductor interface in two-dimensional materials: a generalized theoretical approach

A wave-packet time evolution method, based on the split-operator technique, is developed to investigate the scattering of quasi-particles at a normal-superconductor interface of arbitrary profile and shape. As a practical application, we consider a system where low energy electrons can be described as Dirac particles, which is the case for most two-dimensional materials, such as graphene and transition metal dichalcogenides. However the method is easily adapted for other cases such as electrons in few layer black phosphorus, or any Schrödinger quasi-particles within the effective mass approximation in semiconductors. We employ the method to revisit Andreev reflection in graphene, where specular and retro reflection cases are observed for electrons scattered by a step-like superconducting region. The effect of opening a zero-gap channel across the superconducting region on the electron and hole scattering is also addressed, as an example of the versatility of the technique proposed here.

cond-mat.mes-hall↗