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V. A. Sidorov

Publications and source records attributed to V. A. Sidorov.

At least 37 records · Page 2Linked to original sources
arXiv2011

Textured Superconducting State in the Heavy Fermion CeRhIn5

Anisotropic, spatially textured electronic states often emerge when the symmetry of the underlying crystalline structure is lowered. However, the possibility recently has been raised that novel electronic quantum states with real-space texture could arise in strongly correlated systems even without changing the underlying crystalline structure. Here we report evidence for such texture in the superconducting quantum fluid that is induced by pressure in the heavy-fermion compound CeRhIn5. When long-range antiferromagnetic order coexists with unconventional superconductivity, there is a significant temperature difference between resistively- and thermodynamically-determined transitions into the superconducting state, but this difference disappears in the absence of magnetism. Anisotropic transport behaviour near the superconducting transition in the coexisting phase signals the emergence of textured superconducting planes that are nucleated preferentially along the {100} planes and that appear without a change in crystal symmetry. We show that CeRhIn5 is not unique in exhibiting a difference between resistive and bulk superconducting transition temperatures, indicating that textured superconductivity may be a general consequence of coexisting orders.

cond-mat.str-el↗
arXiv2009

Presure-Induced Superconducting State of Antiferromagnetic CaFe$_2$As$_2$

The antiferromagnet CaFe$_2$As$_2$ does not become superconducting when subject to ideal hydrostatic pressure conditions, where crystallographic and magnetic states also are well defined. By measuring electrical resistivity and magnetic susceptibility under quasi-hydrostatic pressure, however, we find that a substantial volume fraction of the sample is superconducting in a narrow pressure range where collapsed tetragonal and orthorhombic structures coexist. At higher pressures, the collapsed tetragonal structure is stabilized, with the boundary between this structure and the phase of coexisting structures strongly dependent on pressure history. Fluctuations in magnetic degrees of freedom in the phase of coexisting structures appear to be important for superconductivity.

cond-mat.supr-con↗
arXiv2009

Interplay between magnetism and superconductivity and appearance of a second superconducting transition in alpha-FeSe at high pressure

We synthesized tetragonal alpha-FeSe by melting a powder mixture of iron and selenium at high pressure. Subsequent annealing at normal pressure results in removing traces of hexagonal beta- FeSe, formation of a rather sharp transition to superconducting state at Tc ~ 7 K, and the appearance of a magnetic transition near Tm = 120 K. Resistivity and ac-susceptibility were measured on the annealed sample at hydrostatic pressure up to 4.5 GPa. A magnetic transition visible in ac-susceptibility shifts down under pressure and the resistive anomaly typical for a spin density wave (SDW) antiferromagnetic transition develops near the susceptibility anomaly. Tc determined by the appearance of a diamagnetic response in susceptibility, increases linearly under pressure at a rate dTc/dP = 3.5 K/GPa. Below 1.5 GPa, the resistive superconducting transition is sharp; the width of transition does not change with pressure; and, Tc determined by a peak in drho/dT increases at a rate ~ 3.5 K/GPa. At higher pressure, a giant broadening of the resistive transition develops. This effect cannot be explained by possible pressure gradients in the sample and is inherent to alpha-FeSe. The dependences drho(T)/dT show a signature for a second peak above 3 GPa which is indicative of the appearance of another superconducting state in alpha-FeSe at high pressure. We argue that this second superconducting phase coexists with SDW antiferromagnetism in a partial volume fraction and originates from pairing of charge carriers from other sheets of the Fermi surface.

cond-mat.supr-con↗
arXiv2009

Isotropic Quantum Scattering and Unconventional Superconductivity

Superconductivity without phonons has been proposed for strongly correlated electron materials that are tuned close to a zero-temperature magnetic instability of itinerant charge carriers. Near this boundary, quantum fluctuations of magnetic degrees of freedom assume the role of phonons in conventional superconductors, creating an attractive interaction that glues electrons into superconducting pairs. Here we show that superconductivity can arise from a very different spectrum of fluctuations associated with a local or Kondo-breakdown quantum-critical point that is revealed in isotropic scattering of charge carriers and a sub-linear temperature-dependent electrical resistivity. At this critical point, accessed by applying pressure to the strongly correlated, local-moment antiferromagnet CeRhIn5, magnetic and charge fluctuations coexist and produce electronic scattering that is maximal at the optimal pressure for superconductivity. This previously unanticipated source of pairing glue opens possibilities for understanding and discovering new unconventional forms of superconductivity.

cond-mat.str-el↗
arXiv2008

Investigation of the $e^+e^- \to ωπ^0 \to π^0 π^0 γ$ reaction in the energy domain near the $ϕ$-meson

The $e^+e^- \to ωπ^0 \to π^0 π^0 γ$ process was investigated in the SND experiment at the VEPP-2M collider. A narrow energy interval near the $ϕ$-meson was scanned. The observed cross-section reveals, at the level of three standard deviation, the interference effect caused by $ϕ\to π^0π^0γ$ decay. The cross-section parameters, as well as the real and imaginary parts of the $ϕ$-meson related amplitude, were measured.

hep-ex↗
arXiv2007

Electrodynamics near the Metal-to-Insulator Transition in V3O5

The electrodynamics near the metal-to-insulator transitions (MIT) induced, in V3O5 single crystals, by both temperature (T) and pressure (P) has been studied by infrared spectroscopy. The T- and P-dependence of the optical conductivity may be explained within a polaronic scenario. The insulating phase at ambient T and P corresponds to strongly localized small polarons. Meanwhile the T-induced metallic phase at ambient pressure is related to a liquid of polarons showing incoherent dc transport, in the P-induced metallic phase at room T strongly localized polarons coexist with partially delocalized ones. The electronic spectral weight is almost recovered, in both the T and P induced metallization processes, on an energy scale of 1 eV, thus supporting the key-role of electron-lattice interaction in the V3O5 metal-to-insulator transition.

cond-mat.str-el↗
arXiv2006

Study of the $e^+e^-\toηγ$ process with SND detector at the VEPP-2M $e^+e^-$ collider

In experiment with the SND detector at VEPP-2M $e^+e^-$ collider the $e^+e^-\toηγ$ cross section was measured in the energy range $E$=0.60--1.38 GeV with the integrated luminosity of 27.8 pb$^{-1}$. The measured cross section is well described by the vector meson dominance model with contributions from the $ρ(770)$, $ω(783)$, $ϕ(1020)$, $ρ^{\prime}(1465)$ resonances and agrees with results of previous measurements. The decay probabilities $\BR(ϕ\toηγ)$, $\BR(ω\toηγ)$ and $\BR(ρ\toηγ)$ were measured with the accuracies better than or comparable to the world averages.

hep-ex↗
arXiv2006

Pion Form Factor at SND (new edition)

The update of the e^+e^-\toπ^+π^- process cross section, measured in the energy region \sqrt{s}<1 GeV with SND detector at VEPP-2M collider is presented.

hep-ex↗
arXiv2006

Pressure-tuned First-order Phase Transition and Accompanying Resistivity Anomaly in CeZn_{1-δ}Sb_{2}

The Kondo lattice system CeZn_{0.66}Sb_{2} is studied by the electrical resistivity and ac magnetic susceptibility measurements at several pressures. At P=0 kbar, ferromagnetic and antiferromagnetic transitions appear at 3.6 and 0.8 K, respectively. The electrical resistivity at T_N dramatically changes from the Fisher-Langer type (ferromagnetic like) to the Suzaki-Mori type near 17 kbar, i.e., from a positive divergence to a negative divergence in the temperature derivative of the resistivity. The pressure-induced SM type anomaly, which shows thermal hysteresis, is easily suppressed by small magnetic field (1.9 kOe for 19.8 kbar), indicating a weakly first-order nature of the transition. By subtracting a low-pressure data set, we directly compare the resistivity anomaly with the SM theory without any assumption on backgrounds, where the negative divergence in dρ/dT is ascribed to enhanced critical fluctuations in the presence of superzone gaps.

cond-mat.str-el↗
arXiv2006

Anomalous Pressure Dependence of Kadowaki-Woods ratio and Crystal Field Effects in Mixed-valence YbInCu4

The mixed-valence (MV) compound YbInCu4 was investigated by electrical resistivity and ac specific heat at low temperatures and high pressures. At atmospheric pressure, its Kadowaki-Woods (KW) ratio, A/γ^2, is 16 times smaller than the universal value R_{KW}(=1.0 x 10^-5 μΩcm mol^2 K^2 mJ^-2), but sharply increases to 16.5R_{KW} at 27 kbar. The pressure-induced change in the KW ratio and deviation from R_{KW} are analyzed in terms of the change in f-orbital degeneracy N and carrier density n. This analysis is further supported by a dramatic change in residual resistivity ρ_0 near 25 kbar, where ρ_0 jumps by a factor of 7.

cond-mat.str-el↗
arXiv2005

New results on e+e- -> hadrons exclusive cross sections from experiments with SND detector at VEPP-2M e+e- collider in the energy range sqrt(s)=0.4-1.4 GeV

New results of the e+e- -> pi+pi-, K+K-, K_SK_L, pi0/gamma, eta0/gamma processes cross section measurements are presented. The results are based on the 30 pb^-1 data, accumulated by SND detector at VEPP-2M e+e- collider in the energy range sqrt(s)=0.4-1.4 GeV during 1995-2000 years. The comparison with existing experimental data shows that the measurement accuracy is close to or better than the world average. For the e+e- -> pi+pi- process the accuracy is about 0.01. This is important for calculation of hadronic contribution into the muon anomalous magnetic moment.

hep-ex↗
arXiv2005

Study of the process $e^+e^- \to π^+π^-$ in the energy region 400<\sqrt[]{s}<1000 MeV

The cross section of the process e^+e^-\to π^+π^- was measured in the SND experiment at the VEPP-2M collider in the energy region 400<\sqrt[]{s}<1000 MeV. This measurement was based on about 12.4 \times 10^6 selected collinear events, which include 7.4\times 10^6 e^+e^-\to e^+e^-, 4.5\times 10^6 e^+e^-\toπ^+π^- and 0.5\times 10^6 e^+e^-\toμ^+μ^- selected events. The systematic uncertainty of the cross section determination is 1.3 %. The ρ-meson parameters were determined: m_ρ=774.9\pm 0.4\pm 0.5 MeV, Γ_ρ=146.5\pm 0.8\pm 1.5 MeV, σ(ρ\toπ^+π^-)=1220\pm 7\pm 16 nb as well as the parameters of the G-parity suppressed decay ω\toπ^+π^-: σ(ω\toπ^+π^-)=29.9\pm 1.4\pm 1.0 nb and ϕ_{ρω} = 113.5\pm 1.3\pm 1.7 degree.

hep-ex↗
arXiv2004

Superconducting and Normal State Properties of Heavily Hole-Doped Diamond

We report measurements of the specific heat, Hall effect, upper critical field and resistivity on bulk, B-doped diamond prepared by reacting amorphous B and graphite under high-pressure/high-temperature conditions. These experiments establish unambiguous evidence for bulk superconductivity and provide a consistent set of materials parameters that favor a conventional, weak coupling electron-phonon interpretation of the superconducting mechanism at high hole doping.

cond-mat.supr-con↗
arXiv2004

High pressure investigation of the heavy-fermion antiferromagnet U_3Ni_5Al_19

Measurements of magnetic susceptibility, specific heat, and electrical resistivity at applied pressures up to 55 kbar have been carried out on single crystals of the heavy-fermion antiferromagnet U_3Ni_5Al_19, which crystallizes in the Gd_3Ni_5Al_19 orthorhombic structure with two inequivalent U sites. At ambient pressure, a logarithmic T-dependence of the specific heat and T-linear electrical resistivity below 5 K indicates non-Fermi liquid (NFL) behavior in the presence of bulk antiferromagnetic order at T_N=23 K. Electrical resistivity measurements reveal a crossover from non-Fermi liquid to Fermi liquid behavior at intermediate pressures between 46 kbar and 51 kbar, followed by a return to NFL T^{3/2} behavior at higher pressures. These results provide evidence for an ambient pressure quantum critical point and an additional antiferromagnetic instability at P_c=60 kbar.

cond-mat.str-el↗