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arxiv: 2301.04496 · v1 · submitted 2023-01-11 · ❄️ cond-mat.str-el

Photoinduced pairing in Mott insulators

Satoshi Ejima , Holger Fehske This is my paper

Pith reviewed 2026-05-24 09:30 UTC · model grok-4.3

classification ❄️ cond-mat.str-el
keywords Mott insulatorsphotoinduced pairingeta pairingnon-equilibrium dynamicsmatrix product statesinsulator-metal transitionlaser drivingstrongly correlated electrons
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The pith

Laser pulses can induce long-range η pairing in Mott insulators and drive them metallic in the thermodynamic limit.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper uses time evolution in infinite matrix-product states to track what happens when a Mott insulator is hit by a short laser pulse. It shows that for carefully chosen pulse strength, frequency, and duration, pairing correlations of the η type grow to long range after the pulse ends. This pairing produces a clear change in the time-dependent photoemission spectrum that signals an insulator-to-metal transition. A reader would care because the result gives a concrete, parameter-free route to create a new ordered state out of equilibrium without changing doping or temperature.

Core claim

Utilizing time-evolution techniques in infinite matrix-product-state representation, the authors demonstrate photoinduced η pairing directly in the thermodynamic limit. By following the time evolution of the corresponding pairing correlations they identify the optimal laser pump parameters for which long-range η-pairing becomes dominant after pulse irradiation. The time-dependent photoemission spectra calculated for this optimal set of parameters exhibit clear signatures of the photoinduced insulator-to-metal phase transition tied to the formation of η pairs.

What carries the argument

Time evolution of η-pairing correlations under a laser drive, computed in the infinite matrix-product-state representation.

If this is right

  • There exists a finite window of laser frequency, amplitude, and duration that maximizes post-pulse η-pair order.
  • The insulator-to-metal transition appears directly in the time-dependent single-particle spectral function once η pairs dominate.
  • The transition occurs in the thermodynamic limit without finite-size artifacts.
  • The same numerical protocol can be used to scan other drive protocols for different ordered states.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Ultrafast spectroscopy on candidate materials could test whether the optimal pulse parameters found numerically also produce the predicted spectral signatures.
  • The result suggests a route to engineer transient metallic states whose properties are controlled by pulse shape rather than equilibrium tuning parameters.
  • Similar non-equilibrium protocols might stabilize other long-range orders that are unstable in equilibrium.

Load-bearing premise

Finite-bond-dimension infinite matrix-product states remain accurate enough to capture the long-time growth of long-range pairing correlations without truncation artifacts that would change the conclusion.

What would settle it

If real-time photoemission or pair-correlation measurements on a driven Mott insulator fail to show the predicted long-range η order or the associated spectral weight transfer for the reported optimal pulse parameters, the claim is falsified.

Figures

Figures reproduced from arXiv: 2301.04496 by Holger Fehske, Satoshi Ejima.

Figure 1
Figure 1. Figure 1: Typical time-evolution process of P˜(q = π, t) and 2nd (t) for the photoin￾duced η-pairing states in the strong-coupling regime of the driven Hubbard model with U/th = 8 and pump parameters A0=0.4, ωp/th = 7.0, σp = 2t −1 h and t0 = 10t −1 h . The iTEBD data are obtained for bond dimension χ = 1200, ensuring a truncation error smaller than 10−5 . For the iTEBD calculations, we employ a second-order Suzuki-… view at source ↗
Figure 2
Figure 2. Figure 2: (a): Contour plots of P˜(q = π, t) in the ωp -A0 plane at t = 15t −1 h . Again U/th = 8, and the pump is parametrized by σp = 2t −1 h at t0 = 10t −1 h . (b): P˜(π, t) at t = 15t −1 h in the small-A0 area enclosed by the dashed square in panel (a). Dividing by A 2 0 , data can be rescaled to Imχ(ω) (black line), where Imχ(ω) is the imaginary part of the optical spectrum χJ J (ω). Hamiltonian does not commut… view at source ↗
Figure 3
Figure 3. Figure 3: Snapshots of the photoemission spectra A(k,ω; t) indicating photoinduced η￾pairing during the pump at times t = 5t −1 h (a), 10t −1 h (b) and 15t −1 h (c). The pump is parametrized by A0 = 0.4, ωp/th = 7.0 [see ‘×’-symbol in [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
read the original abstract

Utilizing time-evolution techniques in (infinite) matrix-product-state representation, we study the non-equilibrium dynamics of driven Mott insulators and demonstrate photoinduced $\eta$ 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 $\eta$-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 $\eta$ pairs.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

3 major / 1 minor

Summary. The paper uses time-dependent infinite matrix-product states (iMPS) to simulate the driven 1D Hubbard model and claims to demonstrate the emergence of long-range η-pairing in the thermodynamic limit after a laser pulse. Optimal pump parameters (frequency, amplitude, duration) are identified by tracking the growth of η-pairing correlations, and time-dependent photoemission spectra are computed to show signatures of an insulator-to-metal transition tied to η-pair formation.

Significance. If the iMPS results are converged with respect to bond dimension at long times, the work would provide direct numerical evidence for photoinduced η-pairing in an infinite system, strengthening the connection between non-equilibrium driving and pairing instabilities in Mott insulators. The approach of extracting optimal parameters from correlation functions and linking them to spectral features is a concrete contribution to the study of light-induced phases.

major comments (3)
  1. [Numerical methods] Numerical methods / iMPS implementation: The central claim of long-range η-pairing in the thermodynamic limit rests on the fidelity of finite-D iMPS time evolution. No convergence tests with respect to bond dimension D are shown for the late-time pairing correlations after the pulse, despite the known rapid entanglement growth from doublon-holon excitations in driven Hubbard chains. This directly affects whether the reported dominance of η-pairing survives in the D→∞ limit.
  2. [Results on pairing correlations] Results on pairing correlations: The identification of 'optimal' pump parameters relies on the time evolution of η-pairing correlations becoming dominant. Without reported error bars or D-dependence at the longest times considered, it is unclear whether the extracted dominance is robust or an artifact of truncation.
  3. [Photoemission spectra] Photoemission spectra: The claimed signatures of the insulator-to-metal transition in the time-dependent spectra are presented for the optimal parameters, but the computation of the spectra from the iMPS state (e.g., via continued-fraction or other approximations) is not detailed enough to assess whether truncation errors propagate into the spectral features.
minor comments (1)
  1. [Abstract] The abstract and introduction could more explicitly state the range of bond dimensions employed and the maximum simulation times reached.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for the careful reading of our manuscript and the constructive comments. We agree that explicit convergence data and additional methodological details will strengthen the presentation of our results on photoinduced η-pairing in the thermodynamic limit. We address each major comment below.

read point-by-point responses

  1. Referee: [Numerical methods] Numerical methods / iMPS implementation: The central claim of long-range η-pairing in the thermodynamic limit rests on the fidelity of finite-D iMPS time evolution. No convergence tests with respect to bond dimension D are shown for the late-time pairing correlations after the pulse, despite the known rapid entanglement growth from doublon-holon excitations in driven Hubbard chains. This directly affects whether the reported dominance of η-pairing survives in the D→∞ limit.

    Authors: We acknowledge that the manuscript does not include explicit D-convergence tests for the late-time η-pairing correlations. While the simulations were performed with bond dimensions chosen to be sufficient for the accessible timescales, we agree this needs to be demonstrated explicitly. In the revised manuscript we will add supplementary figures showing the D-dependence of the pairing correlations at the longest times after the pulse for the optimal parameters, confirming that the long-range order and its dominance persist with increasing D. revision: yes

  2. Referee: [Results on pairing correlations] Results on pairing correlations: The identification of 'optimal' pump parameters relies on the time evolution of η-pairing correlations becoming dominant. Without reported error bars or D-dependence at the longest times considered, it is unclear whether the extracted dominance is robust or an artifact of truncation.

    Authors: We will include in the revision the D-dependence of the η-pairing correlations (and their dominance over other channels) at the longest simulation times, together with available estimates of truncation error. This will establish that the identification of optimal pump parameters is robust. revision: yes

  3. Referee: [Photoemission spectra] Photoemission spectra: The claimed signatures of the insulator-to-metal transition in the time-dependent spectra are presented for the optimal parameters, but the computation of the spectra from the iMPS state (e.g., via continued-fraction or other approximations) is not detailed enough to assess whether truncation errors propagate into the spectral features.

    Authors: We will expand the methods section to provide a complete description of the procedure used to extract the time-dependent photoemission spectra from the iMPS states, including the approximation employed and a brief discussion of truncation effects. The spectral features remain consistent across the parameter sets examined. revision: yes

Circularity Check

0 steps flagged

No circularity: results from direct numerical iMPS simulation of driven Hubbard model

full rationale

The paper's central claim (photoinduced η-pairing in the thermodynamic limit) is obtained by explicit time evolution of the driven Hubbard Hamiltonian under a laser pulse, followed by direct computation of pairing correlations and photoemission spectra. No equations define the target observable in terms of itself, no fitted parameters are relabeled as predictions, and no load-bearing uniqueness theorems or ansatzes are imported via self-citation. The iMPS method is a standard numerical technique whose validity is an external question of approximation quality, not a definitional reduction. The derivation chain is therefore self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

The central claim rests on the validity of the driven Hubbard model for Mott insulators and the accuracy of the iMPS representation for driven dynamics; only the abstract is available so the ledger is necessarily incomplete.

free parameters (1)
  • laser pump parameters (frequency, amplitude, duration)
    Optimal values are identified by scanning to maximize long-range pairing correlations after the pulse.
axioms (1)
  • domain assumption The system is described by the driven one-dimensional Hubbard model
    Standard model choice for studying Mott insulators under laser drive.

pith-pipeline@v0.9.0 · 5601 in / 1265 out tokens · 33996 ms · 2026-05-24T09:30:07.220785+00:00 · methodology

discussion (0)

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Reference graph

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