arXiv subjects

A. N. Titov

Publications and source records attributed to A. N. Titov.

11 recordsLinked to original sources

arXiv2021

The crystal structure, chemical bonding and magnetic properties of the intercalation compounds Cr$_x$ZrTe$_2$ ($x$ = 0-0.3)

New intercalation compounds Cr$_x$ZrTe$_2$ were synthesized in the Cr concentration range of x=0-0.3. A thorough study of the crystal and electronic structure has been performed. It was found that there is competition in the distribution of the Cr atoms over the octa- and tetrahedral sites in the van der Waals gap, depending on the Cr content. The ordering of the Cr atoms was found at x = 0.25; at the same time, the lattice symmetry decreases from trigonal P-3m1 to monoclinic F2/m. This ordering stabilizes the octahedral coordination of the Cr atoms by Te atoms. The analysis of the experimental data on the electronic structure and DOS calculations showed that the Cr 3d states are spin-split.

cond-mat.mtrl-sci↗

arXiv2016

NbS$_{3}$: A unique quasi one-dimensional conductor with three charge density wave transitions

Through transport, compositional and structural studies, we review the features of the charge-density wave (CDW) conductor of NbS$_{3}$ (phase II). We highlight three central results: 1) In addition to the previously reported CDW transitions at $T_{P1}$ = 360\,K and $T_{P2}$ = 150\,K, another CDW transition occurs at a much higher temperature $T_{P0}$ = 620-650\,K; evidence for the non-linear conductivity of this CDW is presented. 2) We show that CDW associated with the $T_{P2}$ - transition arises from S vacancies acting as donors. Such a CDW transition has not been observed before. 3) We show exceptional coherence of the $T_{P1}$-CDW at room-temperature. Additionally, we report on the effects of uniaxial strain on the CDW transition temperatures and transport.

cond-mat.str-el↗

arXiv2015

The electronic structure formation of CuxTiSe2 in a wide range (0.04 < x < 0.8) of copper concentration

An experimental study of the electronic structure of copper intercalated titanium dichalcogenides in a wide range of copper concentrations (x = 0.05 - 0.6) using the x-rays photoemission spectroscopy, resonant photoemission and x-rays absorption spectroscopy has been performed. Negative energy shifts of the Ti 2p and Se 3d core levels spectra and a corresponding decrease of the photon energy in Ti 2p absorption spectra with increasing concentration of copper have been found. Such sign-anomalous shifts may be explained by the shielding effect of the corresponding atomic shells as a result of the dynamic charge transfer during the formation of a covalent chemical bond between the copper atoms and the TiSe2 matrix.

cond-mat.mtrl-sci↗

arXiv2011

Resonant photoemission at the absorption edge of Mn and Ti and electronic structure of 1T-Mn$_{0.2}$TiSe$_2$

Resonant valence-band X-ray photoelectron spectra (ResPES) excited near 2p$_{3/2}$ core level energies, 2p X-ray photoelectron spectra (XPS) and L$_{3,2}$ X-ray absorption spectra (XAS) of Ti and Mn in single crystal of 1T-Mn$_2$TiSe$_2$ were studied for the first time. The ionic-covalent character of bonds formed by Mn atoms with the neighboring Se atoms in the octahedral coordination is established. From the XPS and XAS measurements compared with results of atomic multiplet calculations of Ti and Mn L$_{3,2}$ XAS it is found that Ti atoms are in ionic state of 4+ and Mn atoms are in the state of 2+. In ResPES of Mn$_{0.2}$TiSe$_2$ excited near Ti 2p$_{3/2}$ and Mn 2p$_{3/2}$ absorption edges the Ti 3d and Mn 3d bands at binding energies just below the Fermi level are observed. According to band structure calculations E$(\textbf{k})$ the Ti 3d states are localized in the vicinity of $\mathsfΓ$ point and the Mn 3d states are localized along the direction K-$\mathsfΓ$-M in the Brillouin zone of the crystal.

cond-mat.mtrl-sci↗

arXiv2011

MxTiSe2 (M = Cr, Mn, Cu) electronic structure study by methods of resonant X-ray photoemission spectroscopy and X-Ray absorption spectroscopy

Electronic structure and chemical bonding in TiX2 (X=S, Se, Te), TMxTiSe2 (TM=Cr, Mn, Cu) and CrxTi1-xSe2 were studied by x-ray resonance photoemission and absorption spectroscopy. These methods are detected to be strong sensitive to chemical bonding. Charge transfer from the intercalated atoms to Ti 3d band is detected. Narrow Ti 3d and Cu 3d bands are observed under Fermi level in CuxTiSe2.

cond-mat.str-el↗

arXiv2010

Evolution of electronic structure on Transition Metal doped Titanium Disulfide by angle-resolved photoemission spectroscopy study

We have systematically investigated the structural property and electrical structures of the transition metal intercalated titanium disulfide compound Fe$_x$TiS$_2$ ($0\leq x\leq0.33$) from angle-resolved photoelectron spectroscopy with tunable polarized synchrotron radiation. The effect of intercalation on the energy bands and density of states of the host material around two high-symmetry points ($Γ, L$) is studied. Charge transfer from the Fe atoms to the dichalcogenide layers leads to the movement of the Ti 3d-derived electron pocket. Two hybridized states are observed around $\sim500$ meV and Fermi level. Knowledge of hybridization among the Fe $3d$, Ti $3d$, and S $3p$ states is very important to understand the physical of Fe$_x$TiS$_2$ system.

cond-mat.mtrl-sci↗

arXiv2009

Dramatic effective mass reduction driven by strong electronic correlations

We present angle-resolved photoemission experiments on 1T-TiSe2 at temperatures ranging from 13K to 288K. The data evidence a dramatic renormalization of the conduction band below 100K, whose origin can be explained with the exciton condensate phase model. The renormalization translates into a substantial effective mass reduction of the dominant charge carriers and can be directly related to the low temperature downturn of the resistivity of 1T-TiSe2. This observation is in opposition to the common belief that strong interactions produce heavier quasiparticles through an increased effective mass.

cond-mat.str-el↗

arXiv2009

Synthesis, crystal growth and superconducting properties of Fe-Se system

Single crystals FeSex were grown in an evacuated sealed quartz tube using polycrystalline material by gas-transport reaction with I2 as a gas-carrier. Crystals with hexagonal-prismatic, tetragonal-prismatic, planar-square and hexagonal faceting 0.1 to 0.5 mm in size were obtained. The electronic transport and magnetic prop-erties measurements of FeSex single crystal exhibit an onset of superconducting transition Tc at up to 24 K.

cond-mat.supr-con↗

arXiv2009

Temperature dependent photoemission on 1T-TiSe2: Interpretation within the exciton condensate phase model

The charge density wave phase transition of 1T-TiSe2 is studied by angle-resolved photoemission over a wide temperature range. An important chemical potential shift which strongly evolves with temperature is evidenced. In the framework of the exciton condensate phase, the detailed temperature dependence of the associated order parameter is extracted. Having a mean-field-like behaviour at low temperature, it exhibits a non-zero value above the transition, interpreted as the signature of strong excitonic fluctuations, reminiscent of the pseudo-gap phase of high temperature superconductors. Integrated intensity around the Fermi level is found to display a trend similar to the measured resistivity and is discussed within the model.

cond-mat.str-el↗

arXiv2009

Effects of pressure-induced phase transitions on superconductivity in the single crystal Fe1.02Se

The temperature dependence of the ac susceptibility for single-crystalline Fe1.02Se has been measured at high pressures to 6.7 GPa. The superconducting transition temperature Tc displays a large increase from 7 K to 30 K in the two-phase region at 0.5 - 1 GPa. Further increase in pressure results in the decrease of Tc. The destruction of superconductivity near 7 GPa is presumably related to a structural transition from orthorhombic to hexagonal. .

cond-mat.supr-con↗

arXiv2000

Electronic structure of Co_xTiSe_2 and Cr_xTiSe_2

The results of investigations of intercalated compounds Cr_xTiSe_2 and Co_xTiSe_2 by X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES) are presented. The data obtained are compared with theoretical results of spin-polarized band structure calculations. A good agreement between theoretical and experimental data for the electronic structure of the investigated materials has been observed. The interplay between the M3d--Ti3d hybridization (M=Cr, Co) and the magnetic moment at the M site is discussed. A 0.9 eV large splitting of the core Cr2p{3/2} level was observed, which reveals a strong exchange magnetic interaction of 3d-2p electrons of Cr. In the case of a strong localization of the Cr3d electrons (for x<0.25), the broadening of the CrL spectra into the region of the states above the nominal Fermi level was observed and attributed to X-ray re-emission. The measured kinetic properties are in good accordance with spectral investigations and band calculation results.

cond-mat.mtrl-sci↗