arXiv subjects

Aleksandr Seliverstov

Publications and source records attributed to Aleksandr Seliverstov.

4 recordsLinked to original sources

arXiv2026

Spectral Fingerprints of Resonant Defect Scattering by Substitutional Mn in Graphene

Using substitutional Mn in graphene/Cu(111) as a model point defect, we combine scanning tunneling microscopy (STM) and angle-resolved photoemission spectroscopy (ARPES) to test the predicted fingerprints of resonant scattering. As the Mn concentration increases to 0.44%, the Dirac point stretching reaches 0.52 eV, while momentum broadening remains energy independent. These spectral fingerprints classify substitutional Mn as a strong resonant scatterer and establish the combination of STM and ARPES as a powerful approach to identify and characterize resonant disorder in graphene.

cond-mat.mes-hall↗

arXiv2026

Radiotracer photoluminescence for element-specific identification of color centers

We report on the implementation of a radiotracer photoluminescence spectroscopy setup at the ISOLDE radioactive ion beam facility at CERN, enabling element-specific identification of optically active defects in solids. The method combines radioactive ion implantation with optical spectroscopy, allowing the temporal evolution of photoluminescence signals to be correlated directly with nuclear decay. The setup is currently optimized for color centers in diamond and related wide-bandgap materials and enables room-temperature measurements. The system consists of an optical microscope coupled to a fiber-fed Czerny-Turner spectrometer with a liquid-nitrogen-cooled CCD detector, providing the stability required for long-duration measurements. As a proof-of-principle, radioactive $^{75}$Ga was implanted into diamond as a precursor to produce $^{75}$Ge impurities. The photoluminescence band extending from 600 nm, corresponding to the well-known GeV$^{-}$ center, exhibits an exponential decay with a half-life of $82.3^{+2.5}_{-2.3} \mathrm{min}$, in agreement with the known $β^{-}$ decay half-life of $^{75}$Ge of $82.78(4) \mathrm{min}$. This establishes a direct and unambiguous correlation between the observed spectral feature and its germanium origin. These results demonstrate the capability of the setup to perform element-specific optical spectroscopy and extend radiotracer methods to color centers in wide-bandgap materials, taking advantage of the uniquely broad range of radioactive isotopes available at ISOLDE.

physics.ins-det↗

arXiv2025

Coexistence of topological surface states and superconductivity in Dirac semimetal NiTe$_2$

The coexistence of topological bands around the Fermi level ($E_F$) and superconductivity provides a fundamental platform for exploring their interplay. However, few materials inherently display both properties. In this study, we demonstrate the coexistence of topological surface states at the $E_F$ and superconductivity in NiTe$_2$ single crystals, a material hitherto not recognized as superconducting. Quasiparticle interference measurements performed via scanning tunneling microscopy suggest the presence of topological surface states at the $E_F$, which is further corroborated by density functional theory simulations. Experimental evidence for superconductivity is provided via electronic transport measurements and specific heat capacity analyses. Our results suggest that NiTe$_2$ represents a promising platform for investigating the rich interplay between topological states and superconductivity.

cond-mat.supr-con↗

arXiv2021

Non-trivial quantum magnetotransport oscillations in pure and robust topological $α$-Sn films

We report experimental evidence of topological Dirac fermion charge carriers in pure and robust $α$-Sn films grown on InSb substrates. This evidence was acquired using standard macroscopic four-point contact resistance measurements, conducted on uncapped films with a significantly reduced bulk mobility. We analyzed and compared electrical characteristics of the constituting components of the $α$-Sn/InSb sample, and propose a three-band drift velocity model accordingly. A surface band, with low carrier density and high mobility, is identified as the origin of the observed Shubnikov -- de Haas oscillations. The analysis of these quantum oscillations results in a non-trivial value of the phase shift $γ=0$, characteristic for topologically protected Dirac fermions. For the same uncapped samples we estimate the momentum relaxation time $τ\approx 300\ \mathrm{fs}$, which is significantly larger in comparison with the previous reports on grown $α$-Sn films.

cond-mat.mtrl-sci↗