Based on the nonperturbative many-body time-dependent approach, photoinduced Hubbard band mixing by ultrashort laser pulse is found in a one-dimensional half-filled Hubbard model through the optical conductivity. The nonlinear development of Drude-like (metallic) weight in the resonant optical pumping (${\ensuremath{\omega}}_{\mathrm{pu}}\ensuremath{\approx}{E}_{g}$; ${\ensuremath{\omega}}_{\mathrm{pu}}$ is the pumping laser energy and ${E}_{g}$ is the gap energy) indicates reconstruction and mixing of the upper and lower Hubbard bands, in contrast to the case of linear development in off-resonant pumping $({\ensuremath{\omega}}_{\mathrm{pu}}⪢{E}_{g})$ where the rigid band picture is valid. The photoemission response after the ultrashort pulse confirms our finding.Based on the nonperturbative many-body time-dependent approach, photoinduced Hubbard band mixing by ultrashort laser pulse is found in a one-dimensional half-filled Hubbard model through the optical conductivity. The nonlinear development of Drude-like (metallic) weight in the resonant optical pumping (${\ensuremath{\omega}}_{\mathrm{pu}}\ensuremath{\approx}{E}_{g}$; ${\ensuremath{\omega}}_{\mathrm{pu}}$ is the pumping laser energy and ${E}_{g}$ is the gap energy) indicates reconstruction and mixing of the upper and lower Hubbard bands, in contrast to the case of linear development in off-resonant pumping $({\ensuremath{\omega}}_{\mathrm{pu}}⪢{E}_{g})$ where the rigid band picture is valid. The photoemission response after the ultrashort pulse confirms our finding.

Physical Review BNov 28, 200716 citations

Photo-induced Metallic States in a Mott Insulator

Takashi Oka

Bulletin of the American Physical SocietyMar 13, 20080 citations

Photoemission signatures of photoinduced carriers and excitons in one-dimensional Mott insulators

Taiga Nakamoto, Yuta Murakami, Naoto Tsuji

We theoretically study photoemission spectra for photodoped one-dimensional Mott insulators that can host excitons, and show that their spectral characteristics differ qualitatively from those of photodoped semiconductors. In conventional semiconductors, photoemission spectra are well understood; free charge carriers generate spectral weight near the bottom of the conduction band, while the formation of excitons leads to replica features of the valence band appearing inside the band gap. In one-dimensional Mott insulators, on the other hand, strong correlations give rise to fractionalized elementary excitations-spinons, holons, and doublons-which fundamentally modify the photoemission response. We find that when photodoped carriers, i.e., doublons and holons, remain unbound, the photoemission spectrum directly reflects the dispersion of spinons, i.e., magnetic elementary excitations. In contrast, when a doublon and a holon form an excitonic bound state, replica structures of the lower Hubbard band emerge inside the Mott gap, carrying contributions from both spinon and holon excitations. Importantly, the distribution of the in-gap signal depends sensitively on the degree of doublon-holon binding. The origin of these spectral features is clarified through a combination of exact diagonalization and the slave-particle approach. These results indicate that photoemission from photoinduced carriers and excitons in strongly correlated electron systems can provide information on magnetic properties and carrier-binding properties.We theoretically study photoemission spectra for photodoped one-dimensional Mott insulators that can host excitons, and show that their spectral characteristics differ qualitatively from those of photodoped semiconductors. In conventional semiconductors, photoemission spectra are well understood; free charge carriers generate spectral weight near the bottom of the conduction band, while the formation of excitons leads to replica features of the valence band appearing inside the band gap. In one-dimensional Mott insulators, on the other hand, strong correlations give rise to fractionalized elementary excitations-spinons, holons, and doublons-which fundamentally modify the photoemission response. We find that when photodoped carriers, i.e., doublons and holons, remain unbound, the photoemission spectrum directly reflects the dispersion of spinons, i.e., magnetic elementary excitations. In contrast, when a doublon and a holon form an excitonic bound state, replica structures of the lower Hubbard band emerge inside the Mott gap, carrying contributions from both spinon and holon excitations. Importantly, the distribution of the in-gap signal depends sensitively on the degree of doublon-holon binding. The origin of these spectral features is clarified through a combination of exact diagonalization and the slave-particle approach. These results indicate that photoemission from photoinduced carriers and excitons in strongly correlated electron systems can provide information on magnetic properties and carrier-binding properties.

arXiv:2603.18982Physical review. B./Physical review. BJun 12, 20260 citations

Symmetry of Photoexcited States in Two-Dimensional Mott Insulators

Takami Tohyama

Bulletin of the American Physical SocietyMar 15, 20060 citations

Photoinduced phase switching from Mott insulator to metallic state in the quarter-filled Peierls-Hubbard model

Can Shao, Takami Tohyama, Hantao Lu

Utilizing the exact diagonalization method, we investigate the one-dimensional Peierls-Hubbard model at quarter filling, where it manifests as an antiferromagnetic Mott insulator in units of dimers. By increasing the on-site Coulomb repulsion $U$ , we observe a significant suppression of the Drude peak, based on a nonequilibrium linear-response theory capable of capturing the zero-frequency (Drude) weight of the optical conductivity under periodic boundary conditions. However, after the ultrafast photoirradiation of this model with large $U$ , we detect a distinct enhancement of the Drude peak, signifying the onset of a photoinduced insulator-metal transition. Comparing these dynamics with the half-filled Hubbard model and a noninteracting spinless half-filled Su-Schrieffer-Heeger model (corresponding to the quarter-filled Peierls-Hubbard model with infinite $U$ ), we propose a mechanism for the photoinduced metallic state: The empty-occupied and double-occupied dimers serve as the photoinduced charge carriers, akin to the holons and doublons in the Hubbard model.Utilizing the exact diagonalization method, we investigate the one-dimensional Peierls-Hubbard model at quarter filling, where it manifests as an antiferromagnetic Mott insulator in units of dimers. By increasing the on-site Coulomb repulsion $U$, we observe a significant suppression of the Drude peak, based on a nonequilibrium linear-response theory capable of capturing the zero-frequency (Drude) weight of the optical conductivity under periodic boundary conditions. However, after the ultrafast photoirradiation of this model with large $U$, we detect a distinct enhancement of the Drude peak, signifying the onset of a photoinduced insulator-metal transition. Comparing these dynamics with the half-filled Hubbard model and a noninteracting spinless half-filled Su-Schrieffer-Heeger model (corresponding to the quarter-filled Peierls-Hubbard model with infinite $U$), we propose a mechanism for the photoinduced metallic state: The empty-occupied and double-occupied dimers serve as the photoinduced charge carriers, akin to the holons and doublons in the Hubbard model.

arXiv:2406.01110Physical review. B./Physical review. BDec 10, 20241 citation

{E}_{g}

is the gap energy) indicates reconstruction and mixing of the upper and lower Hubbard bands, in contrast to the case of linear development in off-resonant pumping $({\ensuremath{\omega}}_{\mathrm{pu}}⪢{E}_{g})$ where the rigid band picture is valid. The photoemission response after the ultrashort pulse confirms our finding.

U

, we observe a significant suppression of the Drude peak, based on a nonequilibrium linear-response theory capable of capturing the zero-frequency (Drude) weight of the optical conductivity under periodic boundary conditions. However, after the ultrafast photoirradiation of this model with large

U

, we detect a distinct enhancement of the Drude peak, signifying the onset of a photoinduced insulator-metal transition. Comparing these dynamics with the half-filled Hubbard model and a noninteracting spinless half-filled Su-Schrieffer-Heeger model (corresponding to the quarter-filled Peierls-Hubbard model with infinite

U

), we propose a mechanism for the photoinduced metallic state: The empty-occupied and double-occupied dimers serve as the photoinduced charge carriers, akin to the holons and doublons in the Hubbard model.