Photoinduced magnetic bound state in an itinerant correlated electron system with a spin-state degree of freedom

Abstract

Photo-excited state in correlated electron system with spin-state degree of freedom is studied. We start from the two-orbital extended Hubbard model where energy difference between the two orbitals is introduced. Photo-excited metastable state is examined based on the effective model Hamiltonian derived by the two-orbital Hubbard model. Spin-state change is induced by photoirradiation in the low-spin band insulator near the phase boundary. High-spin state is stabilized by creating a ferromagnetic bound state with photo-doped hole carriers. An optical absorption occurs between the bonding and antibonding orbitals inside of the bound state. Time-evolution for photo-excited states is simulated in the time-dependent mean-field scheme. Pair-annihilations of the photo-doped electron and hole generate the high-spin state in a low-spin band insulator. We propose that this process is directly observed by the time-resolved photoemission experiments.

Phase diagram and collective excitations in an excitonic insulator from an orbital physics viewpoint

“…These three phases, the LS, AFM-HS and LS/HS ordered phases, in the two-orbital Hubbard model have been shown in Refs. [36,37,47]. Note that the spin alignments in the LS/HS ordered phase are not fixed in the present MF approximation, and the long-range exchange interactions are necessary to determine the spin structure.…”

“…The equivalent Hamiltonians were examined in Refs. [25,36,37]. We mention the symmetry and conservation quantities in the effective Hamiltonian given by Eq.…”

“…The formers are identified as the transverse excitations, which originate At the end of this subsection, we show the magnetic susceptibilities, which are derived from the dynamical spin correlation function given in Eq. (37). The transverse and longitudinal components of the susceptibilities, χ xx and χ zz , are shown in Fig.…”

Photoinduced Hund excitons in the breakdown of a two-orbital Mott insulator

“…The breakdown depends not only on the field strength but also on the Hubbard-U interaction. Light-induced phenomena in two-orbital models have been studied focusing mainly on quarter-filled Mott insulators using double-exchange models [23][24][25][26][27] . A fieldgenerated high-low spin insulator-ferromagnet transition was observed, as well as bound states, and orbital coherent oscillations.…”

Phototunable Magnetism in Copper Octacyanomolybdate

“…In order to see changes in the electronic structures in more detail, we calculate one-particle spectral functions [48]: $\begin{array}{c}D(t;\mathrm{boldk},\omega )=E(t;\mathrm{boldk},\omega )+H(t;\mathrm{boldk},\omega )\end{array}$ with the electron part $\begin{array}{c}E(t;\mathrm{boldk},\omega )=\underset{\mathrm{boldk}\left(\nu \right)=\mathrm{normal1}}{\overset{\mathrm{normal24}N}{{\displaystyle false\sum }}}\delta (\hslash \omega -{\epsilon }_{\mathrm{boldk}0.75em0.75em(\nu 0.75em0.75em)})\langle \mathrm{\Phi }\left(t\right)|{\tilde{c}}_{\mathbf{k}\left(\nu \right)}^{†}{\tilde{c}}_{\mathbf{k}\left(\nu \right)}|\mathrm{\Phi }\left(t\right)\rangle ,\mathrm{\hspace{0.17em}\hspace{0.17em}}\mathrm{\hspace{0.17em}\hspace{0.17em}}\end{array}$ and the hole part $\begin{array}{c}H(t;\mathrm{boldk},\omega )=\underset{\mathrm{boldk}\left(\nu \right)=\mathrm{normal1}}{\overset{\mathrm{normal24}N}{{\displaystyle false\sum }}}\delta (\hslash \omega -{\epsilon }_{\mathrm{boldk}0.75em0.75em(\nu 0.75em0.75em)})\langle \mathrm{\Phi }\left(t\right)|{\tilde{c}}_{\mathbf{k}\left(\nu \right)}{\tilde{c}}_{\mathbf{k}\left(\nu \right)}^{†}|\mathrm{\Phi }\left(t\right)\rangle .\end{array}$ Here, ${\tilde{c}}_{\mathbf{k}(\nu )}^{†}$ creates an electron in the eigenstate of energy ε k ( ν ) for the instantaneous Hamiltonian H HF ( t ) and the delta function is Lorentzian-broadened with a width of 0.1 t MoCu . Figure 8 visualizes D ( t ; k , ω...…”