arXiv subjects

V. N. Ivanovski

Publications and source records attributed to V. N. Ivanovski.

4 recordsLinked to original sources

arXiv2022

Enhanced Superconductivity and Electron Correlations in Intercalated ZrTe$_3$

Charge density waves (CDWs) with superconductivity, competing Fermi surface instabilities and collective orders, have captured much interest in two-dimensional van der Waals (vdW) materials. Understanding of CDW suppression mechanism, its connection to emerging superconducting state and electronic correlations provides opportunities for engineering the electronic properties of vdW heterostructures and thin film devices. Using combination of the thermal transport, X-ray photoemission spectroscopy, Raman measurements, and first-principle calculations, we observe an increase in electronic correlations of the conducting states as CDW is suppressed in ZrTe$_3$ with 5\% Cu and Ni intercalation in the vdW gap. As superconductivity emerges, intercalation brings decoupling of quasi-one-dimensional conduction electrons with phonons as a consequence of intercalation-induced lattice expansion but also a drastic increase in Zr$^{2+}$ at the expense of Zr$^{4+}$ metal atoms. These observation demonstrate the potential of atomic intercalates in vdW gap for ground state tuning but also illustrate the crucial role of Zr metal valence in formation of collective electronic orders.

cond-mat.supr-con↗

arXiv2022

Thermoelectricity and electronic correlations enhancement in FeS by slight Se substitution

We report thermoelectric studies of FeS$_{1-x}$Se$_x$ ($x$ = 0, 0.06) superconducting single crystals that feature high irreversibility fields and critical current density $J_c$ comparable to materials with much higher superconducting critical temperatures ($T_c$'s). The ratio of $T_c$ to the Fermi temperature $T_F$ is very small indicating weak electronic correlations. With a slight selenium substitution on sulfur site in FeS both $T_c$/$T_F$ and the effective mass $m^*$ rise considerably, implying increase in electronic correlation of the bulk conducting states. The first-principle calculations show rise of the density of states at the Fermi level in FeS$_{0.94}$Se$_{0.06}$ when compared to FeS which is related not only to Fe but also to chalcogen-derived electronic states.

cond-mat.supr-con↗

arXiv2018

Critical behavior of the van der Waals bonded ferromagnet Fe$_{3-x}$GeTe$_2$

The critical properties of the single-crystalline van der Waals bonded ferromagnet Fe$_{3-x}$GeTe$_2$ were investigated by bulk dc magnetization around the paramagnetic (PM) to ferromagnetic (FM) phase transition. The Fe$_{3-x}$GeTe$_2$ single crystals grown by self-flux method with Fe deficiency $x \approx 0.36$ exhibit bulk FM ordering below $T_c = 152$ K. The Mössbauer spectroscopy was used to provide information on defects and local atomic environment in such crystals. Critical exponents $β= 0.372(4)$ with a critical temperature $T_c = 151.25(5)$ K and $γ= 1.265(15)$ with $T_c = 151.17(12)$ K are obtained by the Kouvel-Fisher method whereas $δ= 4.50(1)$ is obtained by a critical isotherm analysis at $T_c = 151$ K. These critical exponents obey the Widom scaling relation $δ= 1+γ/β$, indicating self-consistency of the obtained values. With these critical exponents the isotherm $M(H)$ curves below and above the critical temperatures collapse into two independent universal branches, obeying the single scaling equation $m = f_\pm(h)$, where $m$ and $h$ are renormalized magnetization and field, respectively. The exponents determined in this study are close to those calculated from the results of the renormalization group approach for a heuristic model of three-dimensional Heisenberg ($d = 3, n = 3$) spins coupled with the attractive long-range interactions between spins that decay as $J(r)\approx r^{-(3+σ)}$ with $σ=1.89$.

cond-mat.str-el↗

arXiv2016

Critical current density and vortex pinning in tetragonal FeS$_{1-x}$Se$_{x}$ ($x=0,0.06$)

We report critical current density ($J_c$) in tetragonal FeS single crystals, similar to iron based superconductors with much higher superconducting critical temperatures ($T_{c}$'s). The $J_c$ is enhanced 3 times by 6\% Se doping. We observe scaling of the normalized vortex pinning force as a function of reduced field at all temperatures. Vortex pinning in FeS and FeS$_{0.94}$Se$_{0.06}$ shows contribution of core-normal surface-like pinning. Reduced temperature dependence of $J_c$ indicates that dominant interaction of vortex cores and pinning centers is via scattering of charge carriers with reduced mean free path ($δ$$l$), in contrast to K$_x$Fe$_{2-y}$Se$_2$ where spatial variations in $T_{c}$ ($δ$$T_{c}$) prevails.

cond-mat.supr-con↗