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

Rincón, Julián; Dagotto, Elbio; Feiguin, Adrian

doi:10.1103/physrevb.97.235104

Cited by 16 publications

(9 citation statements)

References 43 publications

(79 reference statements)

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“…Subsequent papers confirmed their existence using other methods, like slave particles [16], extensive numerical calculations for the three-orbital model also within the DMFT using the numerical renormalization group (NRG) as the impurity solver [17], or using exact diagonalization to obtain their splitting with J in the OSP [18]. Photoinduced nonequilibrium holon-doublon excitations have been also obtained in a one-dimensional two-orbital version of the model studied here [19], where they were attributed exclusively to the Hund interaction. The structure in the inner edges of the Hubbard bands in the half-filled Hubbard model close to the metal-insulator transition [12,20] has also been characterized as holon-doublon excitations [21], albeit between nearestneighbor sites.…”

Section: Introductionsupporting

confidence: 52%

Subbands in the doped two-orbital Kanamori-Hubbard model

Hallberg

Núñez-Fernández

2020

Phys. Rev. B

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We calculate and resolve with unprecedented detail the local density of states (DOS) and momentumdependent spectral functions at zero temperature of one of the key models for strongly correlated electron materials, the degenerate two-orbital Kanamori-Hubbard model, by means of the dynamical mean-field theory, which uses the density matrix renormalization group as the impurity solver. When the system is hole doped and in the presence of a finite interorbital Coulomb interaction, we find the emergence of a novel holon-doublon in-gap subband which is split by the Hund's coupling. We also observe interesting features in the DOS, such as the splitting of the lower Hubbard band into a coherent narrowly dispersing peak around the Fermi energy, and another subband which evolves with the chemical potential. We characterize the main transitions giving rise to each subband by calculating the response functions of specific projected operators and by comparing with the energies in the atomic limit. The detailed results for the spectral functions found in this work pave the way to study with great precision the microscopic quantum behavior in correlated materials.

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Section: Introductionsupporting

confidence: 52%

Subbands in the doped two-orbital Kanamori-Hubbard model

Hallberg

Núñez-Fernández

2020

Phys. Rev. B

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“…Including dynamical phonons is the next move to account for realistic experimental results [75,76]. Time-dependent spectroscopies on systems with modulated hopping [42,77,78] or multi-orbitals [79,80] are also interesting open problems.…”

Section: Resultsmentioning

confidence: 99%

Time-dependent spectral properties of a photoexcited one-dimensional ionic Hubbard model: an exact diagonalization study

Okamoto

2019

New J. Phys.

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Motivated by the recent progress in time-resolved nonequilibrium spectroscopy in condensed matter, we study an optically excited one-dimensional ionic Hubbard model by exact diagonalization. The model is relevant to organic crystals, transition metal oxides, or ultracold atoms in optical lattices. We implement numerical pump-probe measurements to calculate time-dependent conductivity and single-particle spectral functions. In general, short optical excitation induces a metallic behavior imprinted as a Drude peak in conductivity or an in-gap density of states. In a Mott insulator, we find that the induced Drude peak oscillates at the pump frequency and its second harmonic. The former comes from the oscillation of currents, and the latter from the interference of single-and three-photon excited states. In a band insulator, the Drude peak oscillates only at the pump frequency, and quantities such as the double occupancy do not oscillate. The absence of the second harmonic oscillation is due to the degeneracy of multi-photon excited states. The in-gap density of states in both insulators correlates with the Drude weight and the energy absorption for weak pumping. Strong pumping leads to saturation of the in-gap density of states and to suppression of the Drude weight in the Mott regime. We have also checked that the above features are robust for insulators in the intermediate parameter range. Our study demonstrates the distinct natures of the multi-photon excited states in two different insulators.Alternatively, we can regard it as a variant of the Falicov-Kimball model [41] where f-electrons are chargeordered and frozen. Here we ignore the dynamics of the underlying objects that give the staggered modulation. This means that our results are relevant to experimental data for a short period of time before the ionic motion sets in; the model serves as a starting point for further investigation with dynamical phonons. There is also an experimental realization of the model in ultracold atoms [42].We employ an exact diagonalization method to solve the time-dependent Schrödinger equation, and implement numerical pump-probe measurements to obtain time-dependent conductivity [43-45] and singleparticle spectral functions [46,47]. Short optical pulses applied to a Mott insulator (MI) or a band insulator (BI) make the system metallic, which is indicated by a nonzero Drude peak in conductivity. We find that the Drude peak oscillates at the pump frequency in both cases, while also at the second harmonic in the MI. The second harmonic oscillation in the Mott regime is explained by a constructive interference of single-and three-photon excited states. We have confirmed that the distinct dynamic behaviors still appear for intermediate cases unless the energy gap becomes too small. The relation between the in-gap density of states and the Drude weight is also discussed.The paper is organized as follows. In section 2, an ionic Hubbard model is introduced. Section 3 is devoted to the details of the exact diagonalization method and pump...

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“…Wannier-Mott excitons in semiconductors and their subsequent condensation are well understood since the 60's [36][37][38][39] . In strongly correlated systems one finds Frenkel, Mott-Hubbard excitons, and the recently proposed Hund excitons 40,41 , which are more tightly bound objects. Excitonic condensation in strongly correlated models has been studied in a number of scenarios 42 .…”

Section: Introductionmentioning

confidence: 94%

Excitonic density waves, biexcitons, and orbital-selective pairing in two-orbital correlated chains

Yang

Feiguin

2018

Phys. Rev. B

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We present a comprehensive study of a one-dimensional two-orbital model at and below quarterfilling that realizes a number of unconventional phases. In particular, we find an excitonic density wave in which excitons quasi-condense with finite center of mass momentum and an order parameter that changes phase with wave-vector Q. In this phase, excitons behave as hard-core bosons without charge order. In addition, excitons can pair to form bi-excitons in a state that is close to a charge density-wave instability. When pairing dominates over the inter-orbital repulsion, we encounter a regime in which one orbital is metallic, while the other forms a spin gapped superconductor, a genuine orbital selective paired state. All these results are supported by both, analytical and numerical calculations. By assuming a quasi-classical approximation, we solve the three-body holeelectron-spinon problem and show that excitons are held together by forming a bound state with spinons. In order to preserve the antiferromagnetic background, excitons acquire a dispersion that has a minimum away from k = 0. The full characterization of the different phases is obtained by means of extensive density matrix renormalization group calculations.

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

Cited by 16 publications

References 43 publications

Subbands in the doped two-orbital Kanamori-Hubbard model

Subbands in the doped two-orbital Kanamori-Hubbard model

Time-dependent spectral properties of a photoexcited one-dimensional ionic Hubbard model: an exact diagonalization study

Excitonic density waves, biexcitons, and orbital-selective pairing in two-orbital correlated chains

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