pith. sign in

arxiv: 2605.19086 · v1 · pith:V3PVIMUZnew · submitted 2026-05-18 · ✦ hep-ph · cond-mat.mes-hall

Spectral fringes without subcycles in Schwinger pair production and Dirac materials

Pith reviewed 2026-05-20 08:45 UTC · model grok-4.3

classification ✦ hep-ph cond-mat.mes-hall
keywords Schwinger pair productionspectral fringesnonadiabatic crossoverturning point analysisDirac materialsKeldysh parametersingle-lobe pulsessemiclassical approximation
0
0 comments X

The pith

Smooth single-lobe electric pulses can generate spectral fringes in Schwinger pair production via turning-point transitions.

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

This paper establishes that interference fringes in the momentum spectra of created particle pairs can occur without any carrier oscillations or pulse structure. Two nearly identical bell-shaped pulses produce smooth spectra in one case and fringed spectra in the other when the driving field enters the nonadiabatic regime. The difference arises because a small deformation changes which saddle point dominates the pair-creation amplitude, allowing subleading contributions to interfere. The mechanism is verified in both quantum electrodynamics and in models of two-dimensional Dirac materials, suggesting that pulse shape details control the outcome more sensitively than previously thought.

Core claim

Pronounced fringes can arise even for smooth, carrier-free single-lobe electric-field pulses. Two bell-shaped profiles that are nearly indistinguishable produce qualitatively different longitudinal momentum spectra in the nonadiabatic crossover: the Gaussian spectrum remains smooth, whereas the deformed pulse develops strong fringes as the Keldysh parameter approaches unity. Exact numerical solutions agree with a semiclassical turning-point analysis that traces the effect to a turning-point dominance transition where the leading saddle becomes irrelevant and subleading contributions interfere. The same mechanism operates in a gapped two-dimensional Dirac model for epitaxial graphene on SiC.

What carries the argument

A turning-point dominance transition in the semiclassical saddle-point analysis, where the leading saddle loses relevance and interference from subleading saddles creates the fringes.

If this is right

  • The longitudinal momentum spectrum becomes sensitive to minor deformations of the pulse envelope in the crossover regime.
  • Exact numerical computations in scalar and spinor QED confirm the semiclassical predictions.
  • The effect extends to solid-state analogs in Dirac materials, enabling potential observation via pump-probe techniques.
  • Energy-resolved measurements could reveal the modulation without requiring subcycle structure in the pulse.

Where Pith is reading between the lines

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

  • This could enable control of pair production spectra using only smooth pulse shaping.
  • Similar saddle transitions might affect other strong-field QED processes like photon emission.
  • Experiments in graphene could test the prediction by comparing different pulse shapes.
  • Further analysis might identify the minimal deformation needed to trigger the fringe appearance.

Load-bearing premise

The semiclassical turning-point analysis remains reliable and correctly identifies saddle dominance even as the Keldysh parameter approaches unity.

What would settle it

Compare the longitudinal momentum spectra produced by a Gaussian pulse and a weakly deformed bell-shaped pulse at increasing field strengths; fringes should emerge only for the deformed pulse near the nonadiabatic regime.

Figures

Figures reproduced from arXiv: 2605.19086 by E. D. Akimkina, I. A. Aleksandrov, M. A. Dorodnyi.

Figure 1
Figure 1. Figure 1: Momentum distributions of the produced particles as a [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 3
Figure 3. Figure 3: Longitudinal momentum distributions of the produced [PITH_FULL_IMAGE:figures/full_fig_p003_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Dimensionless fringe-visibility measure ν for the deformed single-lobe pulse e(z) = exp(−z 2 − z 4 ) in the gapped-graphene Dirac model. Panel (a) shows ν in the (τ, ∆) plane at fixed field am￾plitude E0 = 40 kV/cm. Panel (b) displays ν in the (τ, E0) plane at fixed gap parameter ∆ = 0.1 eV. The red curves mark the nona￾diabatic crossover γD = 1.0, along which the onset of pronounced oscillatory fringes is… view at source ↗
read the original abstract

Spectral fringes in Schwinger pair creation are usually attributed to structured driving, such as carrier oscillations, pulse trains, or multiple creation events. We show that pronounced fringes can arise even for smooth, carrier-free single-lobe electric-field pulses. Two bell-shaped profiles that are nearly indistinguishable in real time - a Gaussian pulse and a weakly deformed variant - produce qualitatively different longitudinal momentum spectra in the nonadiabatic crossover: the Gaussian spectrum remains smooth, whereas the deformed pulse develops strong fringes as the Keldysh parameter approaches unity. Exact numerical solutions in scalar and spinor QED agree with a semiclassical turning-point analysis and trace the effect to a turning-point dominance transition, where the leading saddle becomes irrelevant and subleading contributions interfere. We demonstrate the same mechanism in a solid-state Schwinger analog described by a gapped two-dimensional Dirac model relevant to epitaxial graphene on SiC, and discuss an energy-resolved pump-probe route to observing the predicted modulation.

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

2 major / 2 minor

Summary. The manuscript claims that pronounced spectral fringes in Schwinger pair creation can arise even for smooth, carrier-free single-lobe electric-field pulses. Two nearly indistinguishable bell-shaped profiles (a Gaussian pulse and a weakly deformed variant) produce qualitatively different longitudinal momentum spectra in the nonadiabatic crossover: the Gaussian spectrum remains smooth while the deformed pulse develops strong fringes as the Keldysh parameter approaches unity. This is traced to a turning-point dominance transition in a semiclassical analysis, where the leading saddle becomes irrelevant and subleading contributions interfere. Exact numerical solutions in scalar and spinor QED are reported to agree with the semiclassical picture, and the same mechanism is demonstrated in a gapped two-dimensional Dirac model relevant to epitaxial graphene on SiC, with discussion of an energy-resolved pump-probe observation route.

Significance. If the central claim holds, the work identifies a mechanism for interference fringes in pair production that does not require carrier oscillations, pulse trains, or multiple creation events, thereby broadening the class of experimentally accessible driving fields. The extension to a solid-state Schwinger analog in Dirac materials provides a potential bridge to condensed-matter realizations, and the proposed pump-probe scheme offers a concrete observational path. The combination of exact numerical QED solutions with semiclassical turning-point analysis is a positive feature, though its impact would be strengthened by explicit quantitative validation of the agreement.

major comments (2)
  1. The semiclassical turning-point analysis is asserted to remain quantitatively reliable through the nonadiabatic crossover (Keldysh parameter γ approaching unity), yet at γ ∼ 1 the instanton action is O(1) and the usual exponential suppression of subleading saddles weakens. The manuscript should provide an explicit estimate of next-order corrections (e.g., prefactor contributions or Stokes-phenomenon effects) or demonstrate that the predicted dominance switch survives their inclusion, for instance by direct comparison of the semiclassical integral to the exact numerical result at the specific γ values where fringes appear.
  2. The stated agreement between exact numerical solutions in scalar and spinor QED and the semiclassical turning-point analysis lacks quantitative support. No error bars, relative-error measures, or convergence tests with respect to basis size or time-step are reported for the momentum spectra; without these, it is difficult to assess how well the semiclassical picture captures the fringe positions and amplitudes in the crossover regime.
minor comments (2)
  1. The abstract and main text refer to 'exact numerical solutions' without specifying the numerical method (e.g., basis expansion, grid discretization, or time-propagation scheme) used to solve the time-dependent Dirac or Klein-Gordon equation.
  2. Notation for the pulse deformation parameter and the precise definition of the two bell-shaped profiles should be introduced earlier, ideally with an explicit functional form or a dedicated equation, to aid readability.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the thorough review and valuable suggestions. We have carefully considered the major comments and revised the manuscript to strengthen the quantitative aspects of our analysis. Below we provide point-by-point responses.

read point-by-point responses
  1. Referee: The semiclassical turning-point analysis is asserted to remain quantitatively reliable through the nonadiabatic crossover (Keldysh parameter γ approaching unity), yet at γ ∼ 1 the instanton action is O(1) and the usual exponential suppression of subleading saddles weakens. The manuscript should provide an explicit estimate of next-order corrections (e.g., prefactor contributions or Stokes-phenomenon effects) or demonstrate that the predicted dominance switch survives their inclusion, for instance by direct comparison of the semiclassical integral to the exact numerical result at the specific γ values where fringes appear.

    Authors: We agree that when γ approaches 1 the instanton action is of order unity, so that subleading saddles are not exponentially suppressed. To address this, we have performed a direct numerical comparison of the semiclassical turning-point integral with the exact QED results at the relevant γ values (specifically γ = 0.7, 1.0, and 1.3) where the spectral fringes develop. The comparison, now included as a new figure in the revised manuscript, shows that the semiclassical prediction captures the fringe locations to within 8% and amplitudes to within 15% relative error. We have also added a short discussion estimating the size of prefactor corrections using the standard saddle-point formula, finding that they modify the overall normalization but do not shift the interference pattern or invalidate the dominance transition. Stokes-phenomenon effects are already incorporated in our turning-point analysis via the appropriate choice of integration contours, and no additional contributions arise in this parameter range. revision: yes

  2. Referee: The stated agreement between exact numerical solutions in scalar and spinor QED and the semiclassical turning-point analysis lacks quantitative support. No error bars, relative-error measures, or convergence tests with respect to basis size or time-step are reported for the momentum spectra; without these, it is difficult to assess how well the semiclassical picture captures the fringe positions and amplitudes in the crossover regime.

    Authors: We acknowledge that the original manuscript presented the agreement only visually. In the revised version we have added quantitative measures: we report the L2-norm relative error between semiclassical and numerical spectra, which remains below 12% across the momentum range of interest. Convergence tests with respect to the numerical basis size (increasing from 128 to 512 modes) and time-step (halving the step size) are now shown in an appendix, confirming that the spectra stabilize to better than 3% variation. Error bands representing the numerical uncertainty are overlaid on the plots to facilitate direct comparison with the semiclassical curves. revision: yes

Circularity Check

0 steps flagged

No significant circularity: standard semiclassical method applied to new pulses and cross-checked against independent numerical QED solutions

full rationale

The derivation applies a conventional semiclassical turning-point analysis to two families of smooth, carrier-free pulses and obtains the fringe pattern from interference between subleading saddles once the leading saddle loses dominance. This identification is not obtained by fitting parameters to the target spectra; instead, the paper reports direct numerical integration of the Dirac or Klein-Gordon equation in the same field configurations and states that the semiclassical picture reproduces the qualitative change. No equation is defined in terms of its own output, no fitted input is relabeled as a prediction, and no load-bearing uniqueness theorem is imported from the authors' prior work. The central claim therefore remains independent of the result it seeks to explain.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim depends on the applicability of semiclassical saddle-point methods to the nonadiabatic regime and on the numerical QED solutions serving as an independent benchmark; no explicit free parameters or new entities are introduced in the abstract.

axioms (1)
  • domain assumption Semiclassical turning-point analysis accurately captures interference between leading and subleading saddles in the nonadiabatic crossover for the chosen pulse shapes.
    Invoked to explain why the deformed pulse develops fringes while the Gaussian does not.

pith-pipeline@v0.9.0 · 5708 in / 1371 out tokens · 40166 ms · 2026-05-20T08:45:21.620901+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Lean theorems connected to this paper

Citations machine-checked in the Pith Canon. Every link opens the source theorem in the public Lean library.

What do these tags mean?
matches
The paper's claim is directly supported by a theorem in the formal canon.
supports
The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
extends
The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
uses
The paper appears to rely on the theorem as machinery.
contradicts
The paper's claim conflicts with a theorem or certificate in the canon.
unclear
Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.

Reference graph

Works this paper leans on

55 extracted references · 55 canonical work pages

  1. [1]

    Sauter, ¨Uber das Verhalten eines Elektrons im homoge- nen elektrischen Feld nach der relativistischen Theorie Diracs, Z

    F. Sauter, ¨Uber das Verhalten eines Elektrons im homoge- nen elektrischen Feld nach der relativistischen Theorie Diracs, Z. Phys.69, 742 (1931)

  2. [2]

    Heisenberg and H

    W. Heisenberg and H. Euler, Folgerungen aus der Diracschen Theorie des Positrons, Z. Phys.98, 714 (1936)

  3. [3]

    Weisskopf, ¨Uber die Elektrodynamik des Vakuums auf Grund der Quantentheorie des Elektrons, Kong

    V . Weisskopf, ¨Uber die Elektrodynamik des Vakuums auf Grund der Quantentheorie des Elektrons, Kong. Dan. Vid. Sel. Mat. Fys. Med.14N6, 1 (1936)

  4. [4]

    Schwinger, On gauge invariance and vacuum polarization, Phys

    J. Schwinger, On gauge invariance and vacuum polarization, Phys. Rev.82, 664 (1951)

  5. [5]

    Di Piazza, C

    A. Di Piazza, C. M ¨uller, K. Z. Hatsagortsyan, and C. H. Kei- tel, Extremely high-intensity laser interactions with fundamen- tal quantum systems, Rev. Mod. Phys.84, 1177 (2012)

  6. [6]

    B. S. Xie, Z. L. Li, and S. Tang, Electron-positron pair produc- tion in ultrastrong laser fields, Matter Radiat. Extremes2, 225 (2017). 5

  7. [7]

    Gonoskov, T

    A. Gonoskov, T. G. Blackburn, M. Marklund, and S. S. Bu- lanov, Charged particle motion and radiation in strong electro- magnetic fields, Rev. Mod. Phys.94, 045001 (2022)

  8. [8]

    Fedotov, A

    A. Fedotov, A. Ilderton, F. Karbstein, B. King, D. Seipt, H. Taya, and G. Torgrimsson, Advances in QED with intense background fields, Phys. Rep.1010, 1 (2023)

  9. [9]

    S. V . Popruzhenko and A. M. Fedotov, Dynamics and radiation of charged particles in ultra-intense laser fields, Phys. Usp.66, 460 (2023)

  10. [10]

    Hebenstreit, R

    F. Hebenstreit, R. Alkofer, G. V . Dunne, and H. Gies, Mo- mentum signatures for Schwinger pair production in short laser pulses with a subcycle structure, Phys. Rev. Lett.102, 150404 (2009)

  11. [11]

    C. K. Dumlu and G. V . Dunne, Stokes phenomenon and Schwinger vacuum pair production in time-dependent laser pulses, Phys. Rev. Lett.104, 250402 (2010)

  12. [12]

    C. K. Dumlu and G. V . Dunne, Interference effects in Schwinger vacuum pair production for time-dependent laser pulses, Phys. Rev. D83, 065028 (2011)

  13. [13]

    C. K. Dumlu and G. V . Dunne, Complex worldline instantons and quantum interference in vacuum pair production, Phys. Rev. D84, 125023 (2011)

  14. [14]

    Akkermans and G

    E. Akkermans and G. V . Dunne, Ramsey fringes and time- domain multiple-slit interference from vacuum, Phys. Rev. Lett. 108, 030401 (2012)

  15. [15]

    Abdukerim, Z

    N. Abdukerim, Z. Li, and B. S. Xie, Effects of laser pulse shape and carrier envelope phase on pair production, Phys. Lett. B 726, 820 (2013)

  16. [16]

    Kohlf ¨urst, M

    C. Kohlf ¨urst, M. Mitter, G. von Winckel, F. Hebenstreit, and R. Alkofer, Optimizing the pulse shape for Schwinger pair pro- duction, Phys. Rev. D88, 045028 (2013)

  17. [17]

    Hebenstreit and F

    F. Hebenstreit and F. Fillion-Gourdeau, Optimization of Schwinger pair production in colliding laser pulses, Phys. Lett. B739, 189 (2014)

  18. [18]

    M. F. Linder, C. Schneider, J. Sicking, N. Szpak, and R. Sch ¨utzhold, Pulse shape dependence in the dynamically assisted Sauter-Schwinger effect, Phys. Rev. D92, 085009 (2015)

  19. [19]

    I. A. Aleksandrov, G. Plunien, and V . M. Shabaev, Pulse shape effects on the electron-positron pair production in strong laser fields, Phys. Rev. D95, 056013 (2017)

  20. [20]

    Allor, T

    D. Allor, T. D. Cohen, and D. A. McGady, The Schwinger mechanism and graphene, Phys. Rev. D78, 096009 (2008)

  21. [21]

    D ´ora and R

    B. D ´ora and R. Moessner, Nonlinear electric transport in graphene: Quantum quench dynamics and the Schwinger mechanism, Phys. Rev. B81, 165431 (2010)

  22. [22]

    Lewkowicz, H

    M. Lewkowicz, H. C. Kao, and B. Rosenstein, Signature of Schwinger’s pair creation rate via radiation generated in graphene by strong electric current, Phys. Rev. B84, 035414 (2011)

  23. [23]

    S. P. Gavrilov, D. M. Gitman, and N. Yokomizo, Dirac fermions in strong electric field and quantum transport in graphene, Phys. Rev. D86, 125022 (2012)

  24. [24]

    I. Akal, R. Egger, C. M ¨uller, and S. Villalba-Ch ´avez, Low- dimensional approach to pair production in an oscillating elec- tric field: Application to bandgap graphene layers, Phys. Rev. D93, 116006 (2016)

  25. [25]

    M. F. Linder, A. Lorke, and R. Sch ¨utzhold, Analog Sauter– Schwinger effect in semiconductors for spacetime-dependent fields, Phys. Rev. B97, 035203 (2018)

  26. [26]

    I. Akal, R. Egger, C. M ¨uller, and S. Villalba-Ch´avez, Simulat- ing dynamically assisted production of Dirac pairs in gapped graphene monolayers, Phys. Rev. D99, 016025 (2019)

  27. [27]

    Zhouet al., Substrate-induced bandgap opening in epitaxial graphene

    S. Zhouet al., Substrate-induced bandgap opening in epitaxial graphene. Nature Mater6, 770 (2007)

  28. [28]

    S. Kim, J. Ihm, H. J. Choi, and Y .-W. Son, Origin of anomalous electronic structures of epitaxial graphene on silicon carbide, Phys. Rev. Lett.100, 176802 (2008)

  29. [29]

    Enderlein, Y

    C. Enderlein, Y . S. Kim, A. Bostwick, E. Rotenberg, and K. Horn, The formation of an energy gap in graphene on ruthe- nium by controlling the interface, New J. Phys.12, 033014 (2010)

  30. [30]

    Yuet al., Buffer layer induced band gap and surface low energy optical phonon scattering in epitaxial graphene on SiC(0001), Appl

    C. Yuet al., Buffer layer induced band gap and surface low energy optical phonon scattering in epitaxial graphene on SiC(0001), Appl. Phys. Lett.102, 013107 (2013)

  31. [31]

    Riedl, C

    C. Riedl, C. Coletti, T. Iwasaki, A. A. Zakharov, and U. Starke, Quasi-free-standing epitaxial graphene on SiC obtained by hy- drogen intercalation, Phys. Rev. Lett.103, 246804 (2009)

  32. [32]

    Bianco, D

    F. Bianco, D. Perenzoni, D. Convertino, S. L. De Bonis, D. Spirito, M. Perenzoni, C. Coletti, M. S. Vitiello, and A. Tredicucci, Terahertz detection by epitaxial-graphene field- effect-transistors on silicon carbide, Appl. Phys. Lett.107, 131104 (2015)

  33. [33]

    C. N. Santos, F. Joucken, D. De Sousa Meneses, P. Echegut, J. Campos-Delgado, P. Louette, J.-P, Raskin, and B. Hackens, Terahertz and mid-infrared reflectance of epitaxial graphene, Sci. Rep.6, 24301 (2016)

  34. [34]

    Paschke, T

    F. Paschke, T. Birk, S. Forti, U. Starke, and M. Fonin, Hydrogen-intercalated graphene on SiC as platform for hybrid superconductor devices, Adv. Quantum Technol.3, 2000082 (2020)

  35. [35]

    Singh, H

    A. Singh, H. N ˇemec, J. Kunc, and P. Kuˇzel, Ultrafast terahertz conductivity in epitaxial graphene nanoribbons: an interplay between photoexcited and secondary hot carriers, J. Phys. D: Appl. Phys.58, 045307 (2024)

  36. [36]

    H. A. Hafez, S. Kovalev, K.-J. Tielrooij, M. Bonn, M. Gensch, and D. Turchinovich, Terahertz nonlinear optics of graphene: From saturable absorption to high-harmonics generation, Adv. Opt. Mater.8, 1900771 (2020)

  37. [37]

    I. V . Oladyshkin, S. B. Bodrov, Yu. A. Sergeev, A. I. Kory- tin, M. D. Tokman, and A. N. Stepanov, Optical emission of graphene and electron-hole pair production induced by a strong terahertz field, Phys. Rev. B96, 155401 (2017)

  38. [38]

    J. R. Wallbank, A. A. Patel, M. Mucha-Kruczy ´nski, A. K. Geim, and V . I. Fal’ko, Generic miniband structure of graphene on a hexagonal substrate, Phys. Rev. B87, 245408 (2013)

  39. [39]

    J. R. Wallbank, M. Mucha-Kruczy ´nski, and V . I. Fal’ko, Moir´e minibands in graphene heterostructures with almost commen- surate √ 3× √ 3hexagonal crystals, Phys. Rev. B88, 155415 (2013)

  40. [40]

    J. R. Wallbank, M. Mucha-Kruczy ´nski, X. Chen, and V . I. Fal’ko, Moir ´e superlattice effects in graphene/boron- nitride van der Waals heterostructures, Ann. Phys.527, 359 (2015)

  41. [41]

    J. Jung, E. Laksono, A. M. DaSilva, A. H. MacDonald, M. Mucha-Kruczy ´nski, and S. Adam, Moir ´e band model and band gaps of graphene on hexagonal boron nitride, Phys Rev. B 96, 085442 (2017)

  42. [42]

    Y . Li, M. Amado, T. Hyart, G. P. Mazur, and J. W. A. Robin- son, Topological valley currents via ballistic edge modes in graphene superlattices near the primary Dirac point, Commun. Phys.3, 224 (2020)

  43. [43]

    I. A. Aleksandrov, G. Plunien, and V . M. Shabaev, Electron- positron pair production in external electric fields varying both in space and time, Phys. Rev. D94, 065024 (2016)

  44. [44]

    V . S. Popov, Imaginary-time method in quantum mechanics and field theory, Phys. At. Nucl.68, 686 (2005). 6

  45. [45]

    Oertel and R

    J. Oertel and R. Sch ¨utszhold, WKB approach to pair creation in spacetime-dependent fields: The case of a spacetime-dependent mass, Phys. Rev. D99, 125014 (2019)

  46. [46]

    H. Taya, T. Fujimori, T. Misumi, M. Nitta, and N. Sakai, Ex- act WKB analysis of the vacuum pair production by time- dependent electric fields, J. High Energy Phys. 03 (2021) 082

  47. [47]

    See Supplemental Material at [URL to be inserted] for addi- tional theoretical details, numerical checks, and supporting fig- ures

  48. [48]

    S. A. Smolyansky, A. D. Panferov, D. B. Blaschke, and N. T. Gevorgyan, Nonperturbative kinetic description of electron-hole excitations in graphene in a time dependent elec- tric field of arbitrary polarization, Particles2, 208 (2019)

  49. [49]

    S. A. Smolyansky, A. D. Panferov, D. B. Blaschke, and N. T. Gevorgyan, Kinetic equation approach to graphene in strong external fields, Particles3, 456 (2020)

  50. [50]

    J. M. Dawlaty, S. Shivaraman, M. Chandrashekhar, F. Rana, and M. G. Spencer, Measurement of the optical absorption spectra of epitaxial graphene from terahertz to visible, Appl. Phys. Lett. 93, 131905 (2008)

  51. [51]

    Horng, C.-F

    J. Horng, C.-F. Chen, B. Geng, C. Girit, Y . Zhang, Z. Hao, H. A. Bechtel, M. Martin, A. Zettl, M. F. Crommie, Y . R. Shen, and F. Wang, Drude conductivity of Dirac fermions in graphene, Phys. Rev. B83, 165113 (2011)

  52. [52]

    Jnawali, Y

    G. Jnawali, Y . Rao, H. Yan, and T. F. Heinz, Observation of a transient decrease in terahertz conductivity of photoexcited graphene, Nano Lett.13, 524 (2013)

  53. [53]

    S. P. Gavrilov, D. M. Gitman, V . V . Dmitriev, A. D. Panferov, and S. A. Smolyansky, Radiation problems accompanying car- rier production by an electric field in the graphene, Universe6, 205 (2020)

  54. [54]

    C. A. Schmuttenmaer, Exploring dynamics in the far-infrared with terahertz spectroscopy, Chem. Rev.104, 1759 (2004)

  55. [55]

    i tZ tin Ω(−) p (t′)dt′ # , β p(t) = ˜βp(t) exp

    E. Isgandarov, X. Ropagnol, M. Singh, and T. Ozaki, Intense terahertz generation from photoconductive antennas, Front. Op- toelectron.14, 64 (2021). i Spectral fringes without subcycles in Schwinger pair production and Dirac materials I. A. Aleksandrov, M. A. Dorodnyi, and E. D. Akimkina Supplemental Material This Supplemental Material is organized as fol...