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pro vyhledávání: '"Karchev, Naoum"'
Autor:
Karchev, Naoum
Considerable experimental skills have been accumulated in the preparation of field-cooled (FC) magnetic materials. This stimulates the search for FC magnetic materials that are superconductors. The article overviews the recent proposed mechanism of s
Externí odkaz:
http://arxiv.org/abs/2308.00470
Autor:
Karchev, Naoum
In the strong coupling Bose-Einstein Condensation (BEC) regime the superconductors have two characteristic temperatures: $T^*$- onset of fermion pairing and $T_{sc}$- onset of superconductivity, such that $T_{sc}
Externí odkaz:
http://arxiv.org/abs/2212.01170
Autor:
Karchev, Naoum
Publikováno v:
Eur. Phys. J. B 95, 46 (2022)
In our desire to give a new suggestion for H-based superconductors experiments we present a theoretical framework for understanding the impact of an applied electric field on pressured hydride superconductors. We study a material at pressure $p$, whe
Externí odkaz:
http://arxiv.org/abs/2203.06036
Autor:
Karchev, Naoum
Publikováno v:
Journal of Physics: Condensed Matter, 33, 495604 (2021)
In the present article we discuss theoretically the emergence of superconductivity in field cooled $FeCr_2S_4$. The chromium electrons form a triplet $t_{2g}$ states and due to antiferromagnetic exchange with the iron spins have Zeeman splitting. App
Externí odkaz:
http://arxiv.org/abs/2111.02765
Autor:
Karchev, Naoum
We present a unified theory of magnetism and superconductivity of $UGe_2$. To this end, we consider part of $5f$ uranium electrons as mostly itinerant and other ones as mostly localized. The main feature that distinguishes the localized from the itin
Externí odkaz:
http://arxiv.org/abs/2004.11179
Autor:
Karchev, Naoum
Publikováno v:
EPL, 129 (2020) 27003
We explore a spin-fermion model with fermion-spin-quadrupolar interaction. In a nematic phase, this interaction reduces to a four-fermion interaction that is a basis of superconductivity. When the coupling constant is positive the superconductivity i
Externí odkaz:
http://arxiv.org/abs/1908.02514
Autor:
Karchev, Naoum
Publikováno v:
Phys.Rev., B 96, 214409 (2017)
If, during the preparation, an external magnetic field is applied upon cooling we say it has been field cooled. A novel mechanism for insulator-metal transition and superconductivity in field-cooled spin-$1/2$ antiferromagnets on bcc lattice is discu
Externí odkaz:
http://arxiv.org/abs/1712.02983
Autor:
Karchev, Naoum, Vetsov, Tsvetan
Publikováno v:
Condens.Matter 2, 31 (2017)
We report the numerical solutions of the system of equations, which describes the electrodynamics of s-wave superconductors, for time independent fields and half-plane superconductor geometry. The results are: i)the applied magnetic field increases t
Externí odkaz:
http://arxiv.org/abs/1607.03331
Autor:
Karchev, Naoum
Publikováno v:
Condens.Matter 2, 20 (2017)
In this paper we give a derivation of a system of equations to describe the electrodynamics of s-wave superconductors. First, we consider a relativistically covariant theory in terms of gauge four-vector electromagnetic potential and scalar complex f
Externí odkaz:
http://arxiv.org/abs/1512.04284
Autor:
Karchev, Naoum
Publikováno v:
EPL, 110 (2015) 27004
A two-sublattice spin-fermion model of ferrimagnetic spinel, with spin-$1/2$ itinerant electrons at the sublattice $A$ site and spin-$s$ localized electrons at the sublattice $B$ site is considered. The exchange between itinerant and localized electr
Externí odkaz:
http://arxiv.org/abs/1412.0450