Browsing by Author "Zyuzin, A. A."
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- Flat band in disorder-driven non-Hermitian Weyl semimetals
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2018-01-18) Zyuzin, A. A.; Zyuzin, A. YuWe study the interplay of disorder and band-structure topology in a Weyl semimetal with a tilted conical spectrum around the Weyl points. The spectrum of particles is given by the eigenvalues of a non-Hermitian matrix, which contains contributions from a Weyl Hamiltonian and complex self-energy due to electron elastic scattering on disorder. We find that the tilt-induced matrix structure of the self-energy gives rise to either a flat band or a nodal line segment at the interface of the electron and hole pockets in the bulk band structure of type-II Weyl semimetals depending on the Weyl cone inclination. For the tilt in a single direction in momentum space, each Weyl point expands into a flat band lying on the plane, which is transverse to the direction of the tilt. The spectrum of the flat band is fully imaginary and is separated from the in-plane dispersive part of the spectrum by the "exceptional nodal ring" where the matrix of the Green's function in momentum-frequency space is defective. The tilt in two directions might shrink a flat band into a nodal line segment with "exceptional edge points." We discuss the connection to the non-Hermitian topological theory. - Photoinduced interfacial chiral modes in threefold topological semimetal
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2019-10-07) Islam, S. K. Firoz; Zyuzin, A. A.We investigate the chiral electronic modes at the interface between two regions of a threefold topological semimetal, which is illuminated by left and right handed elliptically polarized waves. The radiation effects on the band structure of semimetal are analyzed by using Floquet theory. Two distinct solutions of the interface modes are found with the chirality depending on the phase of the irradiation. We also consider the anomalous Hall response, which is attributed to the interband contribution between the dispersionless flat band and conic bands. - RKKY interaction on the surface of three-dimensional Dirac semimetals
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2019-04-03) Kaladzhyan, V.; Zyuzin, A. A.; Simon, P.We study the RKKY interaction between two magnetic impurities located on the surface of a three-dimensional Dirac semimetal with two Dirac nodes in the band structure. By taking into account both bulk and surface contributions to the exchange interaction between the localized spins, we demonstrate that the surface contribution in general dominates the bulk one at distances larger than the inverse node separation due to a weaker power-law decay. We find a strong anisotropy of the surface term with respect to the spins being aligned along the node separation axis or perpendicular to it. In the many impurity dilute regime, this implies formation of quasi-one-dimensional magnetic stripes orthogonal to the node axis. We also discuss the effects of a surface spin-mixing term coupling electrons from spin-degenerate Fermi arcs. - Spin and valley waves in Dirac semimetals with population imbalance
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2019-09-09) Zyuzin, A. A.; Zyuzin, A. YuWe find an intervalley wave collective mode in two- and three-dimensional Dirac semimetals in the presence of a valley population imbalance. The dispersion relation of this mode is gapless, proportional to the square of the wave vector at small frequencies, and inversely proportional to the electron-electron exchange interaction energy. The valley wave serves as an energy gain source for the external field, that generates the intervalley transitions. The spin-wave analog is discussed for the case of a semimetal with nonequilibrium spin orientation.