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D. V. Livanov

Publications and source records attributed to D. V. Livanov.

7 recordsLinked to original sources
arXiv2004

Electronic spectrum and tunnelling properties of multi-wall carbon nanotubes

We develop a general approach to calculations of the electron spectrum of metallic multi-wall carbon nanotubes (MWNT) with arbitrary number of coaxial layers. It is based on the model with singular attractive potential of equidistant conductive cylinders. The knowledge of one-electron spectrum allows to construct the corresponding Green function and then to calculate the entropy and density of states for MWNT. We analyze the tunnelling between the nanotube and normal metal electrode. The possibility of direct determination of one-electron density of states by measurements of the tunnelling conductivity at low temperatures is proved and the necessary restrictions on temperature are formulated. We discuss briefly the conflicting experimental observations of electronic properties of MWNT.

cond-mat.mes-hall↗
arXiv2002

Paraconductivity in Carbon Nanotubes

We report the calculation of paraconductivity in carbon nanotubes above the superconducting transition temperature. The complex behavior of paraconductivity depending upon the tube radius, temperature and magnetic field strength is analyzed. The results are qualitatively compared with recent experimental observations in carbon nanotubes of an inherent transition to the superconducting state and pronounced thermodynamic fluctuations above $T_{c}$. The application of our results to single-wall and multi-wall carbon nanotubes as well as ropes of nanotubes is discussed.

cond-mat.supr-con↗
arXiv2000

Strong compensation of the quantum fluctuation corrections in clean superconductor

The theory of fluctuation conductivity for an arbitrary impurity concentration including ultra-clean limit is developed. It is demonstrated that the formal divergency of the fluctuation density of states contribution obtained previously for the clean case is removed by the correct treatment of the non-local ballistic electron scattering. We show that in the ultra-clean limit ($Tτ\gg \sqrt{\frac{T_c}{T-T_c}}$) the density-of-states quantum corrections are canceled by the Maki-Thompson term and only quasi-classical paraconductivity remains.

cond-mat↗
arXiv1998

The Role of Density of States Fluctuations in the Normal State Properties of High Tc Superconductors

HTS show many puzzling anomalies in their normal state properties. Among them are: - the presence of a peak in the c-axis resistance and its growth in external magnetic field - the anomalous negative magnetoresistance observed above Tc - the deviation from the Korringa law in the temperature dependence of the NMR relaxation rate - the opening of a large pseudo-gap in the c-axis optical conductivity well above Tc - the gap-like tunneling anomalies observed above Tc - the anomalies in the thermoelectric power above Tc We show how all these effects can be explained by the enhanced role played in quasi-2D systems by the fluctuation decrease of the one-electron density of states (DOS) at the Fermi level, and its competition with other fluctuation contributions (AL, MT). The full fluctuation theory in HTS is reviewed and its resuls compared with experimental data.

cond-mat.supr-con↗
arXiv1997

Thermoelectric Effect in High-$T_c$ Superconductors: the Role of Density of States Fluctuations

We study the effect of the density of states (DOS) fluctuations on the thermoelectric coefficient of superconductor above critical temperature. It is shown that in the isotropic case it is the DOS contribution which gives rise to the leading correction to thermoelectric coefficient in spite of previous results where the only Aslamazov-Larkin term was taken into account. This conclusion is valid for an arbitrary impurity concentration.

cond-mat↗