NORMAL AND SUPERCONDUCTING PROPERTIES OF HIGH TEMPERATURE SUPERCONDUCTORS

Group members:
Dr. Sc. Andrei L. Solovjov (Group Leader);
Senior researcher Ph.D Evheniy V. Khrystenko;
Junior researcher Victor B. Stepanov;
Researcher Ph.D Lyudmila V. Omel'chenko; Junior researcher
Evgeniy V. Petrenko.

The main areas of research: study of the transport properties of conducting and superconducting systems with a reduced charge carrier density, such as high-temperature superconductors (HTSCs): cuprates of YBa2Cu3O7-δ type and magnetic FeAs-pnictides and chalcogenides FeSe and FeTeSe; analysis of the excess (fluctuation) conductivity and pseudogap in cuprate and iron-based HTSC clarification of the features of the interplay between superconductivity and magnetism in HTSCs

The main objective of research: to elucidate the main mechanism of superconducting (SC) pairing in HTSCs, which allows one to obtain Cooper pairs at T >> 100 K, in order to obtain HTSCs with even higher, preferably room, temperatures.
Detailed study of the influence of hydrostatic pressure, which is an effective method for studying HTSCs, on the temperature dependences of resistivity, excess (fluctuation) conductivity, pseudogap D*(T) and charge carrier density nf in YBa2Cu3O7-δ single crystals [5], as well as in magnetic HTSCs HoBa2Cu3O7-δ (΅Ho = 10.5΅B) [5] and Y1-xPrxBa2Cu3O7-δ (΅Pr = 2.5΅B) [2] haDs been performed. For the first time, two additional peaks have been found in the D*(T) dependence of HoBa2Cu3O7-δ single crystals [5], which arise due to phase separation caused by defects in the form of twin boundaries. The pressure has been shown to equalize the nf value making peaks disappear.

In order to study the features of the interplay between superconductivity and magnetism in the newest HTSCs, the fluctuation conductivity and pseudogap (PG) of both magnetic superconductors Dy0.6Y0.4Rh3.85Ru0.15B4 [4] and FeSe [1], and YBa2Cu3O7-δ single crystals with an increase in the content of Hf [8], Pr [9], and Ti [10] impurities in them were studied. For the first time, the general behavior of D*(T) was found in all magnetic superconductors, which means that the mechanism of interplay between SC and magnetism is most likely the same in all HTSCs.

The effect of annealing on the PG and charge carrier density of optimally doped YBa2Cu3O7-δ single crystals without twins [3], as well as the low-temperature properties of the MAX phase Ti3AlC2 [6] and of the magnetic compound of the Bi95,69Mn3,69Fe0,62 [7] were studied for the first time, which is important to confirm the hypothesis of the same SP pairing mechanism in all HTSCs.


The list of cited publications of our group (2017 – 2020):

1. Features of excess conductivity and a possible pseudogap in FeSe superconductors / A. L. Solovjov, E. V. Petrenko, L. V. Omelchenko, E. Nazarova and K. Buchkov, and K. Rogacki // LTP – 2020. – 46, 5. – P. 538.
2. Peculiarities of pseudogap in Y1-xPrxBa2Cu3O7-δ single crystals under pressure up to 1.7 GPa / A.L. Soloviov, L.V. Omelchenko, E.V. Petrenko, R.V. Vovk, V.V. Khotkevych, A. Chroneos // Scientific Reports. - 2019. – V. 9, P. 20424 (1-16).
3. Effect off annealing on a pseudogap in untwinned YBa2Cu3O7-δ single crystals / A.L. Soloviov, E.V. Petrenko, L.V. Omelchenko, R.V. Vovk, I.L. Goulatis, A. Chroneos // Scientific Reports. - 2019. – V. 9, P. 9274 (1-13).
4. Features of Excess Conductivity Behavior in a Magnetic Superconductor Dy0.6Y0.4Rh3.85Ru0.15B4 / A. L. Solovjov, A. V. Terekhov, E. V. Petrenko, L. V. Omelchenko, and Zhang Cuiping // LTP – 2019. – 45, P. 1193 – 1201.
5. Electric transport and the pseudogap in the 1-2-3 HTSC system, under all-around compression / R.V. Vovk, A.L. Solovjov // LTP – 2018. – 44, 2. – P. 81-113.
6. Electrical and thermal conductivity of the Ti3AlC2 MAX phase at low temperatures / G.Ya. Khadzhai, R.V. Vovk, T.A. Prichna, E.S. Gevorkyan, M.V. Kislitsa, A.L. Solovjov / LTP – 2018. – 44, 5. – P. 451-452.
7. Features of magnetoresistance and magnetic properties in Bi95,69Mn3,69Fe0,62 / A. V. Terekhov, K. Rogacki, A. L. Solovjov, A. N. Bludov, A. I. Prokhvatilov, V. V. Meleshko, I. V. Zolochevskii, E. V. Khristenko, J. Cwik, A. Los, A. D. Shevchenko, Z. D. Kovalyuk, and O. M. Ivasishin //LTP. –2018. – 44, 11. – P. 1153 – 1160.
8. Effect of Hafnium Impurities on the Magnetoresistance of YBa2Cu3O7-δ / S.V. Savich, A.V. Samoylov, S.N. Kamchatnaya, I.L. Goulatis, R.V. Vovk, A. Chroneos, A.L. Solovjov, L.V. Omelchenko // J LTP – 2017. – V. 186, 3-4. – P. 285 – 293.
9. Pseudogap and fluctuation conductivity in Y1-xPrxBa2Cu3O7-δ single crystals with different concentrations of praseodymium / A. L. Solovjov, L. V. Omelchenko, R. V. Vovk, S. N. Kamchatnaya // LTP. – 2017. – 43, 7. – P. 841-847.
10. Suppression of the order–disorder transition in Ti-doped YBaCuO compounds / S.V Savich, A.V Samoylov, S.N Kamchatnaya, O.V Dobrovolskiy, R.V Vovk, A.L Solovjov, L.V Omelchenko // Materials Science: Materials in Electronics. – 2017. V. 28, 8. – P. 1-5.