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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fedoseev A. D.
Заглавие : Modification of topological corner excitations at the interplay of boundary geometry and Coulomb interaction
Колич.характеристики :9 с
Место публикации : J. Phys. Condens. Matter. - 2023. - Vol. 35, Is. 45. - Ст.455301. - ISSN 09538984 (ISSN), DOI 10.1088/1361-648X/aceddf. - ISSN 1361648X (eISSN)
Примечания : Cited References: 35. - The author thanks S V Aksenov and M M Korovushkin for the fruitful discussions and valuable remarks. The reported study was supported by Russian Science Foundation (Project No. 22-22-20076) and Krasnoyarsk Regional Fund of Science
Аннотация: The effect of Coulomb interaction on the 2D second order topological superconductor is investigated taking into account different geometries of the boundary in the mainframe of the mean-field approximation. The spontaneous symmetry breaking, described earlier in Aksenov et al (2023 Phys. Rev.B 107 125401), is found to be robust against the boundary deformation. Meanwhile, the details of the state with spontaneously broken symmetry is found to be dependent on the specific boundary geometry. Considering different types of the boundary of the 2D system, it is demonstrated that the deviation of the electron density in the broken symmetry state is determined by the position of the zero-dimensional (second-order) excitations with nearly zero energy. The critical value of the Coulomb interaction, at which the transition occurs, is found to be determined by the energy of these excitations, which is non-zero due to overlapping of the wave-functions at different corners.
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aksenov S. V., Fedoseev A. D., Shustin M. S., Zlotnikov A. O.
Заглавие : Effect of local Coulomb interaction on Majorana corner modes: Weak and strong correlation limits
Место публикации : Phys. Rev. B. - 2023. - Vol. 107, Is. 12. - Ст.125401. - ISSN 24699950 (ISSN), DOI 10.1103/PhysRevB.107.125401. - ISSN 24699969 (eISSN)
Примечания : Cited References: 63. - We acknowledge fruitful discussions with D. M. Dzebisashvili and V. A. Mitskan. The reported study was supported by Russian Science Foundation Project No. 22-22-20076, and Krasnoyarsk Regional Fund of Science
Аннотация: Here we present an analysis of the evolution of Majorana corner modes realizing in a two-dimensional higher-order topological superconductor (HOTSC) on a square lattice under the influence of local Coulomb repulsion. Both weak- and strong-interaction regimes are studied. It is shown that in the homogeneous system, the weak repulsion widens the region of the topologically nontrivial phase on the phase diagram. The open-boundary effect, resulting in spatial inhomogeneity of the system, leads to the appearance of the ground-state crossover as the repulsion intensity increases. Before the crossover, concentration correlators are C4 symmetric and spin independent, and the corner states have energies that are determined by the overlap of the excitation wave functions localized at the different corners. After the crossover, the concentration correlators are spin dependent and possess the spontaneously broken symmetry. In turn, the corner excitation energy is size independent and defined by the Coulomb repulsion intensity with a quadratic law. In the strong-repulsion regime we derive the effective HOTSC Hamiltonian in the atomic representation and found a rich variety of interactions induced by virtual processes between the lower and upper Hubbard subbands. It is shown that Majorana corner modes still can be realized in the limit of the infinite repulsion, although the boundaries of the topologically nontrivial phase are strongly renormalized by Hubbard corrections.
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3.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Aksenov S. V., Fedoseev A. D., Shustin M. S., Zlotnikov A. O.
Заглавие : Effect of local coulomb interaction on majorana corner modes
Коллективы : International Conference on Supercondactivity and Magnetism
Место публикации : 8th International conference on supercondactivity and magnetism (ICSM2023): abstract book. - 2023. - P.454
Примечания : Cited References: 4. - РНФ № 22-22-20076
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aksenov S. V., Fedoseev A. D., Shustin M. S., Zlotnikov A. O.
Заглавие : On the Dirac mass of Hubbard fermions in strongly correlated higher-order topological superconductor
Колич.характеристики :8 с
Коллективы : Nanophysics and Nanoelectronics, International Symposium
Место публикации : Phys. Solid State. - 2023. - Vol. 65, Is. 7. - С. 1063-1070. - ISSN 10637834 (ISSN), DOI 10.61011/PSS.2023.07.56391.31H. - ISSN 10906460 (eISSN)
Примечания : Cited References: 28. - The study was supported by the Russian Science Foundation (project No. 22-22-20076), and Krasnoyarsk Regional Fund of Science
Аннотация: Majorana corner modes have a number of advantages over the conventional Majorana states in terms of performing topologically protected quantum computations. However, the problem of the influence of Coulomb repulsion on higher-order phases, which inevitably arises when trying to implement such systems in practice, has been poorly studied. In this article, we analyze the features of a topological invariant describing the nontrivial phase with the corner modes for a two-dimensional two-orbital model of a hybrid structure in the regime of extremely strong electron correlations. For this purpose, approximate wave functions of the edge states with a linear dispersion law and the associated Dirac masses, which arise when superconducting pairing in the system is taken into account, are obtained.
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Shustin M. S., Aksenov S. V., Zlotnikov A. O., Fedoseev A. D., Mitskan V. A., Kagan M. Yu.
Заглавие : Topological superconductivity and Majorana states in low-dimensional systems
Место публикации : Phys.-Usp. - 2022. - Vol. 65, Is. 1. - P.2-39. - ISSN 10637869 (ISSN), DOI 10.3367/UFNe.2021.03.038950
Примечания : Cited References: 320. - This review was prepared in the framework of the Russian Foundation for Basic Research (RFBR) grant 19-12-50087. Part of the presented results were obtained in the framework of RFBR projects 19-02-00348, 20-32-70059, and 20-02-00015. S V A expresses his gratitude for support through a grant from the President of the Russian Federation, MK-1641.2020.2. A O Z and M S Sh express their gratitude to the Theoretical Physics and Math ematics Advancement Foundation “BASIS”. M Yu K thanks the Program for Basic Research of the NationalResearch University Higher School of Economics for support
Аннотация: We discuss the properties of topologically nontrivial superconducting phases and the conditions for their realization in condensed matter, the criteria for the appearance of elementary Majorana-type excitations in solids, and the corresponding principles and experimental methods for identifying Majorana bound states (MBSs). Along with the well-known Kitaev chain and superconducting nanowire (SW) models with spin-orbit coupling in an external magnetic field, we discuss models of quasi-two-dimensional materials in which MBSs are realized in the presence of noncollinear spin ordering. For finite-length SWs, we demonstrate a cascade of quantum transitions occurring with a change in the magnetic field, accompanied by a change in the fermion parity of the ground state. The corresponding anomalous behavior of the magnetocaloric effect can be used as a tool for identifying MBSs. We devote considerable attention to the analysis of the transport characteristics of devices that contain topologically nontrivial materials. The results of studying the conductance of an Aharonov-Bohm ring whose arms are connected by an SW are discussed in detail. An important feature of this device is the appearance of Fano resonances in the dependence of conductance on the magnetic field when the SW is in a topologically nontrivial phase. We establish a relation between the characteristics of such resonances and the spatial structure of the lowest-energy SW state. The conditions for the occurrence of an MBS in the phase of the coexistence of chiral d+id superconductivity and 120-degree spin ordering are determined in the framework of the t-J-V model on a triangular lattice. We take electron-electron interactions into account in discussing the topological invariants of low-dimensional superconducting materials with noncollinear spin ordering. The formation of Majorana modes in regions with an odd value of a topological ℤ invariant is demonstrated. The spatial structure of these excitations in the Hubbard fermion ensemble is determined.
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shustin M. S., Aksenov S. V.
Заглавие : Effect of strong intersite Coulomb interaction on the topological properties of a superconducting nanowire
Место публикации : Phys. Solid State. - 2022. - Vol. 64, Is. 13. - P.2047-2053. - ISSN 10637834 (ISSN), DOI 10.21883/PSS.2022.13.53972.23s. - ISSN 10906460 (eISSN)
Примечания : Cited References: 55. - This study was supported by the Russian Foundation for Basic Research, the Government of the Krasnoyarsk Territory and the Krasnoyarsk Regional Fund of Science, projects nos. 20-42-243001 and 20-42-243005. M.S.S. thanks the Foundation for the Advancement of Theoretical Physics and Mathematics ”BASIS“. S.V.A. is grateful to the Council of the President of the Russian Federation for Support of Young Scientists and Leading Scientific Schools, project No. MK-1641.2020.2
Аннотация: For superconducting nanowire with the pairing of extended s-type symmetry, Rashba spin-orbit interaction in a magnetic field, the influence of strong intersite charge correlations on single-particle Majorana excitations is analyzed. This problem is investigated on the basis of the density matrix renormalization group numerical method. It is shown that with an increase in the repulsion intensity of electrons located at the neighboring sites, two subbands emerge in the lower Hubbard band of the open system. Based on calculations of the Majorana polarization and degeneracy of the entanglement spectrum, it was found that a topologically nontrivial phase with one edge state survives at the edge of each of the subbands where the concentration of electrons or holes is minimal.
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fedoseev A. D.
Заглавие : Realization conditions and the magnetic field dependence of corner excitations in the topological insulator with superconducting coupling on the triangular lattice
Коллективы : Russian Foundation for Basic Research, Government of Krasnoyarsk Territory [19-02-00348]; Krasnoyarsk Regional Fund of Science [20-42-243005]; "Coulomb interactions in the problem of Majorana modes in low-dimensional systems with nontrivial topology" [19-42-240011]; Council of the President of the Russian Federation for Support of Young Scientists and Leading Scientific SchoolsLeading Scientific Schools Program [MK1641.2020.2]
Место публикации : J. Exp. Theor. Phys. - 2021. - Vol. 133, Is. 1. - P.71-76. - ISSN 1063-7761, DOI 10.1134/S1063776121060029. - ISSN 1090-6509(eISSN)
Примечания : Cited References: 38. - This work was supported by the Russian Foundation for Basic Research (project no. 19-02-00348), Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science to the research projects: "Study of edge states in oneand two-dimensional topological superconductors" (no. 20-42-243005), "Coulomb interactions in the problem of Majorana modes in low-dimensional systems with nontrivial topology" (no. 19-42-240011), and Council of the President of the Russian Federation for Support of Young Scientists and Leading Scientific Schools (Project MK1641.2020.2)
Предметные рубрики: EDGE
STATES
ORDER
Аннотация: The studies of the topological properties of systems have recently been extended due to a new concept of higher-order topological insulators and superconductors. Many models were proposed for two-dimensional systems on a square lattice, where corner excitations can appear; however, the problem of existence of such excitations in superconducting systems with a triangular crystal lattice is still poorly understood. Using a topological insulator in the form of a triangle with a chiral superconducting order parameter as an example, we shows that corner excitations can exist in C3-symmetric systems. In spite of a nontopological character, these excitations have energies inside the gap of the first-order edge excitation spectrum over a wide parameter range and are well localized at the corners of the system. Gapless corner excitations are shown to exist in the system at certain parameters. The application of a magnetic field in the system plane removes the triple degeneracy of the corner excitation energy and makes it possible to control the position of the minimum-energy corner excitation using a magnetic field. At the same time the fine adjustment to achieve the gapless excitations at the chosen corner can be made with changing of the magnetic field value.
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Dzebisashvili D. M., Korovushkin M. M., Barabanov A. F.
Заглавие : Spin-polaron concept in the theory of normal and superconducting states of cuprates
Коллективы : Russian Foundation for Basic Research (RFBR)Russian Foundation for Basic Research (RFBR) [18-02-00837, 19-02-00509, 20-32-70059]; Government of Krasnoyarsk Region; Krasnoyarsk Region Science and Technology Support Fund [18-42-240014]; RFBRRussian Foundation for Basic Research (RFBR) [19-12-50116]
Место публикации : Phys. Usp. - 2021. - Vol. 64, Is. 7. - P.641-670. - ISSN 1063-7869, DOI 10.3367/UFNe.2020.08.038829. - ISSN 1468-4780(eISSN)
Примечания : Cited References: 328. - The authors' study was supported by the Russian Foundation for Basic Research (RFBR) within project nos. 18-02-00837, 19-02-00509, and 20-32-70059, and partly by the Government of Krasnoyarsk Region and the Krasnoyarsk Region Science and Technology Support Fund within project no. 18-42-240014 "Single-orbital effective model of an ensemble of spin-polaron quasiparticles in the problem of describing the intermediate state and pseudogap behavior of cuprate superconductors.'' The review was carried out with support from the RFBR within the Expansion competition (project no. 19-12-50116)
Предметные рубрики: HIGH-TC SUPERCONDUCTIVITY
CHARGE-DENSITY-WAVE
HIGH-TEMPERATURE SUPERCONDUCTORS
Аннотация: The review discusses the emergence of the spinfermion model of cuprates and the formation of the spin-polaron concept of the electronic structure of hole-doped cuprate superconductors. This concept has allowed describing the properties of cuprates in the normal phase as well as the features of superconducting pairing in the unified approach. The derivation of the spin-fermion model from the Emery model in the regime of strong electronic correlations is described, demonstrating the appearance of strong coupling between the spins of copper ions and holes on oxygen ions. Such a strong interaction against the background of the singlet state of the spin subsystem of copper ions (quantum spin liquid) leads to the formation of special Fermi quasiparticlesDnonlocal spin polarons. Under doping, the spin-polaron ensemble exhibits instability with respect to superconducting d-wave pairing, whereas superconducting swave pairing is not implemented. At the optimal doping, the transition to the superconducting phase occurs at temperatures corresponding to experimental data. It is shown that the superconducting d-wave pairing of spin-polaron quasiparticles is not suppressed by the Coulomb repulsion of holes located on neighboring oxygen ions. It is emphasized that, when the spectral characteristics of spin-polaron quasiparticles are taken into account, the calculated temperature and doping dependences of the London penetration depth are in good agreement with experimental data.
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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aksenov S. V., Zlotnikov A. O., Shustin M. S.
Заглавие : Strong Coulomb interactions in the problem of Majorana modes in a wire of the nontrivial topological class BDI
Коллективы : RAS Presidium programs for fundamental research [32, 12]; Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR) [18-32-00443, 19-02-00348]; Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science [19-42-240011]; Council of the President of the Russian Federation for Support of Young Scientists and Leading Scientific SchoolsLeading Scientific Schools Program [MK-1641.2020.2, MK-3594.2018.2]; Foundation for the Advancement of Theoretical Physics and Mathematics "BASIS" [18-46-007]
Место публикации : Phys. Rev. B. - 2020. - Vol. 101, Is. 12. - Ст.125431. - ISSN 2469-9950, DOI 10.1103/PhysRevB.101.125431. - ISSN 2469-9969(eISSN)
Примечания : Cited References: 60. - We acknowledge fruitful discussions with V. V. Valkov and V. A. Mitskan. The reported study was funded by the RAS Presidium programs for fundamental research Nos. 12 and 32, Russian Foundation for Basic Research (Projects No. 18-32-00443 and No. 19-02-00348), Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science to the research project: "Coulomb interactions in the problem of Majorana modes in low-dimensional systems with nontrivial topology" (Grant No. 19-42-240011). S.V.A. and A.O.Z. are grateful to the Council of the President of the Russian Federation for Support of Young Scientists and Leading Scientific Schools, Projects No. MK-1641.2020.2 and No. MK-3594.2018.2. S.V.A. acknowledges the support from the Foundation for the Advancement of Theoretical Physics and Mathematics "BASIS" (Grant No. 18-46-007).
Предметные рубрики: QUANTUM
POLARIZATION
TRANSITION
FERMIONS
SPECTRUM
STATE
Аннотация: In this study, the problem of strong Coulomb interactions in topological superconducting wire is analyzed by means of the density-matrix-renormalization-group (DMRG) approach. To analyze properties of edge states in the BDI-class structure, a quantity called Majorana polarization is used. From its dependence on wire length and an entanglement-spectrum degeneracy, topological phase diagrams are obtained. The DMRG calculations for the Shubin-Vonsovsky-type model of the wire show the transformation of phases with Majorana single and double modes (MSMs and MDMs, respectively) under the increase of onsite and intersite correlations. In particular, we demonstrate different scenarios including the possibilities of both induction and suppression of the MSMs and MDMs. It is shown that in the strongly correlated regime, the contributions of single-particle excitations to the Majorana-type states significantly decrease at low magnetic fxields. Moreover, the t-J*-V model is derived allowing to study the effective interactions and improve the DMRG numerics. It is found out that in the limiting case of the effective Hamiltonian with infinitely strong onsite repulsion, t model, the topological phases are destroyed. Finally, the ways to probe the MSMs and MDMs via the features of caloric functions are discussed.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Komarov K. K., Dzebisashvili D. M.
Заглавие : Effect of Coulomb repulsion on the London penetration depth in cuprate superconductors
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR) [18-02-00837, 20-32-70059]; Government of Krasnoyarsk Region; Krasnoyarsk Regional Science and Technology Support Fund [18-42-240014, 18-42-243002]; Council for Grants of the President of the Russian Federation [MK-1641.2020.2]
Место публикации : Phys. Scr. - 2020. - Vol. 95, Is. 6. - Ст.065806. - ISSN 0031-8949, DOI 10.1088/1402-4896/ab8163. - ISSN 1402-4896(eISSN)
Примечания : Cited References: 57. - The work was financially supported by the Russian Foundation for Basic Research (project #18-02-00837, #20-32-70059), the Government of Krasnoyarsk Region, the Krasnoyarsk Regional Science and Technology Support Fund (projects: #18-42-240014 'One-orbit effective model of an ensemble of spin-polaron quasiparticles in the problem of describing the intermediate state and pseudogap behavior of cuprate superconductors' and #18-42-243002 'Manifestation of spin-nematic correlations in spectral characteristics of electronic structure and their influence on practical properties of cuprate superconductors'). The work of KKK was supported by the Council for Grants of the President of the Russian Federation (project MK-1641.2020.2).
Предметные рубрики: ELECTRONIC-STRUCTURE
SUPERFLUID DENSITY
QUASI-PARTICLES
2-BAND MODEL
Аннотация: We study the effect of Coulomb repulsion between oxygen holes on the London penetration depth λ based on the concept of spin-polaron nature of Fermi quasiparticles in cuprates superconductors. It is shown that for the generally accepted values of the parameters of the spin-fermion model, taking into account the Coulomb interaction, both the one-site Hubbard U p and interaction between holes on the next-nearest-neighbor oxygen ions V 2, allows one to achieve a much better agreement of the calculated temperature dependencies of the value λ −2 with the experimental data in La2−x Sr x CuO4 in a wide range around optimal doping.
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