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arXiv:2301.04496 · SciPost Physics Proceedings

Photoinduced pairing in Mott insulators

Satoshi Ejima, Holger Fehske

Published Jun 5, 2023• 0 citations
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Abstract

Utilizing time-evolution techniques in (infinite) matrix-product-state representation, we study the non-equilibrium dynamics of driven Mott insulators and demonstrate photoinduced \eta η pairing directly in the thermodynamic limit. Analyzing the time evolution of the corresponding pairing correlations, we determine the optimal laser pump parameters for which long-range \eta η -pairing becomes dominant after pulse irradiation. The time-dependent photoemission spectra for this optimal pump parameter set show clear signatures of the photoinduced insulator-to-metal phase transition related to the formation of \eta η pairs.

DOI
10.21468/scipostphysproc.11.009

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Utilizing time-evolution techniques in (infinite) matrix-product-state representation, we study the non-equilibrium dynamics of driven Mott insulators and demonstrate photoinduced \eta η pairing directly in the thermodynamic limit. Analyzing the time evolution of the corresponding pairing correlations, we determine the optimal laser pump parameters for which long-range \eta η -pairing becomes dominant after pulse irradiation. The time-dependent photoemission spectra for this optimal pump parameter set show clear signatures of the photoinduced insulator-to-metal phase transition related to the formation of \eta η pairs.
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Entanglement analysis of photoinduced η\etaη-pairing states
Abstract Simulating the von Neumann and second-order Rényi entropies of driven Mott insulators, we examine the entanglement dynamics of the η\etaη η -pairing state in the one-dimensional half-filled Hubbard model after pulse irradiation. Corresponding data are obtained by means of the infinite time-evolving block decimation technique directly in the thermodynamic limit. For optimal pump-pulse parameters the temporal course of the entanglement entropies shows the characteristic entanglement growth due to the increase of η\etaη η -pairing correlations.
Employing the density-matrix renormalization group technique in the matrix-product-state representation, we investigate the photoexcited superconducting correlations induced by the η-pairing mechanism in the half-filled Hubbard chain.We estimate the characteristic pair correlation function and verify the accuracy of our numerical results by comparison with exact-diagonalization data for small systems.The optimal parameter set of the pump that most enhances the η-pair correlations, is calculated in the strong-coupling regime.For such a pump, we explore the possibility of quasi-long-range order.
Utilizing the time-dependent density-matrix renormalization-group technique, we numerically prove photoinduced pairing states in the extended Falicov-Kimball model (EFKM) at half-filling, both with and without internal SU(2) symmetry. In the time-dependent photoemission spectra, an extra band appears above the Fermi energy after pulse irradiation, indicating an insulator-to-metal transition. Even in the absence of the SU(2) structure, the pair correlations are enhanced during the pump, and afterwards they decrease over time. This implies the possible metallization of Ta2NiSe5{\mathrm{Ta}}_{2}\mathrm{Ni}{\mathrm{Se}}_{5}Ta2​NiSe5​, a strong candidate for an excitonic insulator material, for which the EFKM is considered to be the minimal theoretical model. Simulating the photoemission with optimized pulse parameters, we demonstrate a photoinduced quantum phase transition, in accord with recent findings in time- and angle-resolved photoemission spectroscopy experiments on Ta2NiSe5{\mathrm{Ta}}_{2}\mathrm{Ni}{\mathrm{Se}}_{5}Ta2​NiSe5​.
By employing unbiased numerical methods, we show that pulse irradiation can induce unconventional superconductivity even in the Mott insulator of the Hubbard model. The superconductivity found here in the photoexcited state is due to the η-pairing mechanism, characterized by staggered pair-density-wave oscillations in the off-diagonal long-range correlation, and is absent in the ground-state phase diagram; i.e., it is induced neither by a change of the effective interaction of the Hubbard model nor by simple photocarrier doping. Because of the selection rule, we show that the nonlinear optical response is essential to increase the number of η pairs and thus enhance the superconducting correlation in the photoexcited state. Our finding demonstrates that nonequilibrium many-body dynamics is an alternative pathway to access a new exotic quantum state that is absent in the ground-state phase diagram, and also provides an alternative mechanism for enhancing superconductivity.