Related papers: Impurity-induced Ferromagnetism in Doped Triplet E…
Both nonmagnetic and magnetic impurity effects in spin singlet and triplet excitonic insulators were investigated. The bound state energies caused by single impurity were given. The different compositions of the bound states can be used to…
The theory of doped excitonic insulators is reinvestigated in light of recent experiments on hexaborides. For the appropriate valley-degenerate X_3,X_3' band structure, ``intra-valley'' condensation is energetically favored. Ferromagnetism…
A ferromagnet with a small spontaneous moment but with a high Curie temperature can be obtained by doping an excitonic insulator made from a spin triplet exciton condensate. Such a condensate can occur in a semimetal with a small overlap or…
Understanding ferromagnetism mechanism in doped Mott insulators on frustrated lattices remains challenging at intermediate coupling and finite doping. Here, we study the itinerant ferromagnetism and propose its mechanism in doped Mott…
We critically investigate the model of a doped excitonic insulator, which recently has been invoked to explain some experimental properties of the ferromagnetic state in Ca_{1-x}La_xB_6. We demonstrate that the ground state of this model is…
Multiorbital Hubbard models with Hund coupling and crystal-field splitting exhibit an instability toward spin-triplet excitonic order in the parameter regime characterized by strong local spin fluctuations. Upon chemical doping, two…
Measurements of the local density of states near impurities can be useful for identifying the superconducting gap structure in alkali doped iron chalcogenide superconductors K_xFe_{2-y}Se_2. Here, we study the effects of nonmagnetic and…
The surface states of a topological insulator are described by an emergent relativistic massless Dirac equation in 2+1 dimensions. In contrast to graphene, there is an odd number of Dirac points, and the electron spin is directly coupled to…
We investigate the effect of magnetic impurities on the local quasiparticle density of states (LDOS) in iron-based superconductors. Employing the two-orbital model where 3$d$ electron and hole conduction bands are hybridizing with the…
Nesting in a semimetal can lead to an excitonic insulator state with spontaneous coherence between conduction and valence bands and a gap for charged excitations. In this paper we present a theory of the ferromagnetic state that occurs when…
We study impurity bound states and impurity-induced order in the superconducting state of LiFeAs within a realistic five-band model based on the band structure and impurity potentials obtained from density functional theory (DFT). In…
Helical edge states of two-dimensional topological insulators show a gap in the density of states (DOS) and suppressed conductance in the presence of ordered magnetic impurities. Here we will consider the dynamical effects on the DOS and…
We investigate a model of excitonic ordering (i.e electron-hole pair condensation) appropriate for the divalent hexaborides. We show that the inclusion of imperfectly nested electron hole Fermi surfaces can lead to the formation of an…
In contrast to semiconductors doped with transition metal magnetic elements, which become ferromagnetic at temperatures below ~ 100K, semiconductors doped with non-magnetic ions (e.g. silicon doped with phosphorous) have not shown evidence…
We show that the energy gap induced by ferromagnetically aligned magnetic impurities on the surface of a topological insulator can be filled, due to scattering off the non-magnetic potential of the impurities. In both a continuum surface…
We consider an extended spinless Falicov--Kimball model at an arbitrary doping level, focusing on the range of parameter values where a uniform excitonic insulator is stabilised at half-filling. We compare the properties of possible uniform…
We study the presence of impurity bound states within a five-band Hubbard model relevant to iron-based superconductors. In agreement with earlier studies, we find that in the absence of Coulomb correlations there exists a range of repulsive…
We study the effects of strong electron-electron interactions on the surface of cubic topological Kondo insulators (such as samarium hexaboride, SmB$_6$). Cubic topological Kondo insulators generally support three copies of massless Dirac…
An excitonic magnet hosts a condensate of spin-triplet excitons composed of conduction-band electrons and valence-band holes, and may be described by the two-orbital Hubbard model. When the Hamiltonian has the nearest-neighbor interorbital…
Some doped semiconductors have recently been shown to display superconductivity or weak ferromagnetism. Here we investigate the electronic structure and conditions for magnetism in a supercells of cubic XW_{26}O_{81}, where X=Nb,V and Re.…