- Physical Review Journals
All JournalsPhysics Magazine

Physical Review B

Reuse & Permissions

It is not necessary to obtain permission to reuse this article or its components as it is available under the terms of the Creative Commons Attribution 4.0 International license. This license permits unrestricted use, distribution, and reproduction in any medium, provided attribution to the author(s) and the published article's title, journal citation, and DOI are maintained. Please note that some figures may have been included with permission from other third parties. It is your responsibility to obtain the proper permission from the rights holder directly for these figures.

Export citation

Export citation

Choose format for download:

Download Citation
  • Open Access

Transient photoexcited state of the small-gap quasi-two-dimensional Mott-Hubbard insulator Sn/Si(111)−(√3×√3)−R30∘

G. M. Pierantozzi1,*, S. Modesti2,†, M. Perlangeli3, R. Cucini1, S. Fiori4, F. Salvador1, G. Rossi5,1, and G. Panaccione1

  • *Contact author: pierantozzi@iom.cnr.it
  • †Contact author: smodestis1@gmail.com
PDF

Phys. Rev. B 114, 125131 – Published 25 August, 2026

DOI: https://doi.org/10.1103/bc4t-fzc3

Abstract

We investigate the transient response to photodoping of Sn/Si(111)−(√3×√3) R30∘, a simple and prototypical two-dimensional Mott-Hubbard insulator with a small gap on a triangular lattice, by time- and angle-resolved photoemission with a 120 fs time resolution. A transient metallic state forms nearly instantaneously after photoexcitation and persists for a few hundred femtoseconds, consistent with theoretical predictions and previous studies of small-gap Mott systems in one and three dimensions. The temperature dependence of the doublon lifetime indicates that the dominant relaxation mechanism involves coupling between charge and spin degrees of freedom. On a longer timescale, a small energy shift of the lower Hubbard band persists for more than 1 ns. We attribute this long-lived modification to energy renormalization of the Hubbard bands induced by the photoexcited electron-hole plasma in the Si substrate. Our results further demonstrate that substrate excitations and the dynamics of the three-dimensional electron-hole plasma play a significant role in ultrafast studies of two-dimensional materials supported on semiconducting or insulating substrates, while also pointing to a possible route for controlling transient electronic states.

View figure in article

Physics Subject Headings (PhySH)

Article Text

References (60)

  1. Y. Murakami, D. Golěz, M. Eckstein, and P. Werner, Photoinduced nonequilibrium states in Mott insulators, Rev. Mod. Phys. 97, 035001 (2025), and references therein.
  2. C. N. Yang, η pairing and off-diagonal long-range order in a Hubbard model, Phys. Rev. Lett. 63, 2144 (1989).
  3. T. Kaneko, T. Shirakawa, S. Sorella, and S. Yunoki, Photoinduced η-pairing in the Hubbard model, Phys. Rev. Lett. 122, 077002 (2019).
  4. J. Li, D. Golěz, P. Werner, and M. Eckstein, η-paired superconducting hidden phase in photodoped Mott insulators, Phys. Rev. B 102, 165136 (2020).
  5. S. Ray and P. Werner, Photoinduced charge, spin, and orbital order in the two- orbital extended Hubbard model, Phys. Rev. B 110, 214433 (2024).
  6. M. Eckstein, and P. Werner, Thermalization of a pump-excited Mott insulator, Phys. Rev. B 84, 035122 (2011); Ultafast photo-carrier relaxation in Mott insulators with short-range spin correlation, Sci. Rep. 6, 21235 (2016).
  7. J. H. Mentink and M. Eckstein, Ultrafast quenching of the exchange interaction in a Mott insulator, Phys. Rev. Lett. 113, 057201 (2014).
  8. J. Li and M. Eckstein, Nonequilibrium steady-state theory of photodoped Mott insulators, Phys. Rev. B 103, 045133 (2021).
  9. S. Ejima, F. Lange, and H. Fehske, Nonequilibrium dynamics in pumped Mott insulators, Phys. Rev. Res. 4, L012012 (2022).
  10. S. Ray and P. Werner, Photo-induced ferromagnetic and superconducting orders in multi-orbital Hubbard models, Phys. Rev. B 110, L041109 (2024).
  11. K. Kimura, H. Matsuzaki, S. Takaishi, M. Yamashita, and H. Okamoto, Ultrafast photoinduced transitions in charge density wave, Mott insulator, and metallic phases of an iodine-bridged platinum compound, Phys. Rev. B 79, 075116 (2009); S. Iwai, M. Ono, A. Maeda, H. Matsuzaki, H. Kishida, H. Okamoto, and Y. Tokura, Ultrafast optical switching to a metallic state by photoinduced Mott transition in a halogen-bridged nickel-chain compound, Phys. Rev. Lett. 91, 057401 (2003).
  12. H. Okamoto, T. Miyagoe, K. Kobayashi, H. Uemura, H. Nishioka, H. Matsuzaki, A. Sawa, and Y. Tokura, Photoinduced transition from Mott insulator to metal in the undoped cuprates Nd2CuO4 and La2CuO4, Phys. Rev. B 83, 125102 (2011); H. Okamoto, H. Matsuzaki, T. Wakabayashi, Y. Takahashi, and T. Hasegawa, Photoinduced metallic state mediated by spin- charge separation in a one-dimensional organic Mott insulator, Phys. Rev. Lett. 98, 037401 (2007).
  13. D. Fausti, R. I. Tobey, N. Dean, S. Kaiser, A. Dienst, M. C. Hoffmann, S. Pyon, T. Takayama, H. Takagi, and A. Cavalleri, Light-induced superconductivity in a stripe-ordered cuprate, Science 331, 189 (2011).
  14. S. Kaiser, C. R. Hunt, D. Nicoletti, W. Hu, I. Gierz, H. Y. Liu, M. Le Tacon, T. Loew, D. Haug, B. Keimer, and A. Cavalleri, Optically induced coherent transport far above Tc in underdoped YBa2Cu3O6−δ, Phys. Rev. B 89, 184516 (2014).
  15. K. Katsumi, M. Nishida, S. Kaiser, S. Miyasaka, S. Tajima, and R. Shimano, Near-infrared light-induced superconducting-like state in underdoped YBa2Cu3Oy studied by c-axis terahertz third-harmonic generation, Phys. Rev. B 107, 214506 (2023).
  16. T. Suzuki, T. Someya, T. Hashimoto, S. Michimae, M. Watanabe, M. Fujisawa, T. Kanai, N. Ishii, J. Itatani, S. Kasahara, Y. Matsuda, T. Shibauchi, K. Okazaki, and S. Shin, Photoinduced possible superconducting state with long-lived disproportionate band filling in FeSe, Commun. Phys. 2, 115 (2019).
  17. M. Buzzi, D. Nicoletti, M. Fechner, N. Tancogne-Dejean, M. A. Sentef, A. Georges, T. Biesner, E. Uykur, M. Dressel, A. Henderson, T. Siegrist, J. A. Schlueter, K. Miyagawa, K. Kanoda, M.-S. Nam, A. Ardavan, J. Coulthard, J. Tindall, F. Schlawin, D. Jaksch, and A. Cavalleri, Photomolecular high- temperature superconductivity, Phys. Rev. X 10, 031028 (2020).
  18. M. Mitrano, A. Cantaluppi, D. Nicoletti, S. Kaiser, A. Perucchi, S. Lupi, P. D. Pietro, D. Pontiroli, M. Riccò, S. R. Clark, D. Jaksch, and A. Cavalleri, Possible light-induced superconductivity in K3C60 at high temperature, Nature (London) 530, 461 (2016).
  19. M. Ligges, I. Avigo, D. Golež, H. U. R. Strand, Y. Beyazit, K. Hanff, F. Diekmann, L. Stojchevska, M. Kalläne, P. Zhou, K. Rossnagel, M. Eckstein, P. Werner, and U. Bovensiepen, Ultrafast doublon dynamics in photoexcited 1T-TaS2, Phys. Rev. Lett. 120, 166401 (2018).
  20. L. Perfetti, P. A. Loukakos, M. Lisowski, U. Bovevensiepen, M. Wolf, H. Berger, S. Biermann, and A. Georges, Femtosecond dynamics of electronic states in the Mott insulator 1T-TaS2 by time resolved photoelectron spectroscopy, New J. Phys. 10, 053019 (2008).
  21. L. Perfetti, P. A. Loukakos, M. Lisowski, U. Bovensiepen, H. Berger, S. Biermann, P. S. Cornaglia, A. Georges, and M. Wolf, Time evolution of the electronic structure of 1T-TaS2 through the insulator-metal transition, Phys. Rev. Lett. 97, 067402 (2006).
  22. Z. Lenarčič and P. Prelovšek, Ultrafast charge recombination in photoexcited Mott-Hubbard insulators, Phys. Rev. Lett. 111, 016401 (2013); Charge recombination in undoped cuprates, Phys. Rev. B 90, 235136 (2014).
  23. S. M. Gilbertson, T. Durakiewicz, G. L. Dakovski, Y. Li, J.-X. Zhu, S. D. Conradson, S. A. Trugman, and G. Rodriguez, Ultrafast photoemission spectroscopy of the uranium dioxide Mott insulator: Evidence for a robust energy gap structure, Phys. Rev. Lett. 112, 087402 (2014).
  24. D. Nevola, A. Bataller, A. Kumar, S. Sridhar, J. Frick, S. O'Donnell, H. Ade, P. A. Maggard, A. F. Kemper, K. Gundogdu, and D. B. Dougherty, Timescales of excited state relaxation in a-RuCl3 observed by time-resolved two-photon photoemission spectroscopy, Phys. Rev. B 103, 245105 (2021).
  25. G. Lantz, B. Mansart, D. Grieger, D. Boschetto, N. Nilforoushan, E. Papalazarou, N. Moisan, L. Perfetti, V. L. R. Jacques, D. Le Bolloc'h, C. Laulhé, S. Ravy, J-P Rueff, T. E. Glover, M. P. Hertlein, Z. Hussain, S. Song, M. Chollet, M. Fabrizio, and M. Marsi, Ultrafast evolution and transient phases of a prototype out-of-equilibrium Mott–Hubbard material, Nat. Commun. 8, 13917 (2017).
  26. D. Wegkamp, M. Herzog, L. Xian, M. Gatti, P. Cudazzo, C. L. McGahan, R. E. Marvel, R. F. Haglund, Jr., A. Rubio, M. Wolf, and J. Stähler, Instantaneous bandgap collapse in photoexcited monoclinic VO2 due to photocarrier doping, Phys. Rev. Lett. 113, 216401 (2014).
  27. C. Sohrt, A. Stange, M. Bauer, and K. Rossnagel, How fast can a Peierls–Mott insulator be melted? Farad. Discuss. 171, 243 (2014).
  28. C. Piovera, V. Brouet, E. Papalazarou, M. Caputo, M. Marsi, A. Taleb-Ibrahimi, B. J. Kim, and L. Perfetti, Time-resolved photoemission of Sr2IrO4, Phys. Rev. B 93, 241114(R) (2016).
  29. O. Mehio, X. Li, H. Ning, Z. Lenarčič, Y. Han, M. Buchhold, Z. Porter, N. J. Laurita, S. D. Wilson, and D. Hsieh, A Hubbard exciton fluid in a photo-doped antiferromagnetic Mott insulator, Nat. Phys. 19, 1876 (2023).
  30. Y. Kim and J. Lee, Time-resolved photoemission of infinitely periodic atomic arrangements: Correlation-dressed excited states of solids, npj Comput. Mater. 6, 132 (2020).
  31. S. Modesti, L. Petaccia, G. Ceballos, I. Vobornik, G. Panaccione, G. Rossi, L. Ottaviano, R. Larciprete, S. Lizzit, and A. Goldoni, Insulating ground state of Sn/Si(111)−(√3×√3)R30∘, Phys. Rev. Lett. 98, 126401 (2007).
  32. G. Profeta and E. Tosatti, Triangular Mott-Hubbard insulator phases of Sn/Si⁡(111) and Sn/Ge⁡(111) surfaces, Phys. Rev. Lett. 98, 086401 (2007).
  33. A. B. Odobescu, A. A. Maizlakh, N. I. Fedotov, and S. V. Zaitsev-Zotov, Electronic correlation effects and Coulomb gap in the Si(111)−(√3×√3)-Sn surface, Phys. Rev. B 95, 195151 (2017).
  34. F. Ming, S. Johnston, D. Mulugeta, T.  S. Smith, P. Vilmercati, G. Lee, T.  A. Maier, P.  C. Snijders, and H.  H. Weitering, Realization of a hole-doped Mott insulator on a triangular silicon lattice, Phys. Rev. Lett. 119, 266802 (2017).
  35. M. Iannetti, S. Modesti, G. Di Santo, M. Caputo, P. M. Sheverdyaeva, P. Moras, F. Chiapolino, T. Cea, C. Tresca, E. Tosatti, and G. Profeta, The electronic structure of a doped Mott-Hubbard surface, Phys. Rev. B 112, 075159 (2025).
  36. F. Ming, X. Wu, C. Chen, K. D. Wang, P. Mai, T. A. Maier, J. Strockoz, J. W. F. Venderbos, C. González, J. Ortega, S. Johnston, and H. H. Weitering, Evidence for chiral superconductivity on a silicon surface, Nat. Phys. 19, 500 (2023).
  37. Y.-L. Xiong, J.-Q. Guan, R.-F. Wang, C.-L. Song, X.-C. Ma, and Q.-K. Xue, Experimental observation of pseudogap in a modulation- doped Mott insulator: Sn/Si(111)−(√3×√3)R30∘, Chinese Phys. B 31, 067401(2022).
  38. P. Hansmann, T. Ayral, L. Vaugier, P. Werner, and S. Biermann, Long-range Coulomb interactions in surface systems: A first principles description within self-consistently combined GW and dynamical mean field theory, Phys. Rev. Lett. 110, 166401 (2013).
  39. M. Zahedifar and P. Kratzer, Phonon-induced electronic relaxation in a strongly correlated system: The Sn/Si(111) (√3×√3) adlayer revisited, Phys. Rev. B 100, 125427 (2019).
  40. NFFA-Europe, Time-Resolved PES and Spin Polarization (SPRINT), https://www.trieste.nffa.eu/techniques/spectroscopy /time-resolved-pes-and-spin-polarization-sprint/.
  41. R. Cucini,T. Pincelli, G. Panaccione, D. Kopic, F. Frassetto, P. Miotti, G. M. Pierantozzi, S. Peli, A. Fondacaro, A. De Luisa, A. De Vita, P. Carrara, D. Krizmancic, D. T. Payne, F. Salvador, A. Sterzi, L. Poletto, F. Parmigiani, G. Rossi, and F. Cilento, Coherent narrowband light source for ultrafast photoelectron spectroscopy in the 17–31 eV photon energy range, Struct. Dyn. 7, 014313 (2020).
  42. R. I. G. Uhrberg, H. M. Zhang, T. Balasubramanian, S. T. Jemander, N. Lin, and G. V. Hansson, Electronic structure of Sn/Si (111) √3×√3: Indications of a low-temperature phase, Phys. Rev. B 62, 8082 (2000); J. Lobo, A. Tejeda, A. Mugarza, and E. G. Michel, Electronic structure of Sn/Si(111)−(√3×√3) R30∘ as a function of Sn coverage, ibid. 68, 235332 (2003).
  43. M. Alonso, R. Cimino, and K. Horn, Surface photovoltage effects in photoemission from metal-GaP (110) interfaces: Importance for band bending evaluation, Phys. Rev. Lett. 64, 1947 (1990).
  44. H. Dember, Photoelectromotive force in cuprous oxide crystals, Phys. Z. 32, 554 (1931).
  45. Shin-ichiro Tanaka, Utility and constraint on the use of pump-probe photoelectron spectroscopy for detecting time-resolved surface photovoltage, J. Electron Spectrosc. Relat. Phenom. 185, 152 (2012).
  46. T. Zhang, Z.-C. Huang-Fu, Y. Qian, H. Gao, J. B. Brown, and Y. Rao, Photoinduced surface electric fields and surface population dynamics of GaP(100) photoelectrodes, J. Phys. Chem. C 126, 6531 (2022).
  47. S. L. Yang, J. A Sobota, P. S. Kirchmann, and Z. X Shen, Electron propagation from a photo-excited surface: Implications for time-resolved photoemission, Appl. Phys. A 116, 85 (2014).
  48. P. Siffalovic, M. Drescher, and U. Heinzmann, Femtosecond time-resolved core-level photoelectron spectroscopy tracking surface photovoltage transients on p–GaAs, Europhys. Lett. 60, 924 (2002).
  49. P. Vashishta and R. K. Kalia, Universal behavior of exchange-correlation energy in electron-hole liquid, Phys. Rev. B 25, 6492 (1982).
  50. J. Kanasaki, H. Tanimura, K. Tanimura, P. Ries, W. Heckel, K. Biedermann, and T. Fauster, Ultrafast dynamics in photoecited valence-band states of Si studied by time- and angle-resolved photoemission spectroscopy of bulk direct transitions, Phys. Rev. B 97, 035201 (2018).
  51. P. L. Gourley and J. P. Wolfe, Properties of the electron-hole liquid in Si: Zero stress to the high-stress limit, Phys. Rev. B 24, 5970 (1981); J. Bokor and N. J. Halas, Time-resolved study of silicon surface recombination, IEEE J. Quantum Electron. 25, 2550 (1989).
  52. The spectrum measured 1 ps before the pump pulse in the equilibrium MI phase has a residual intensity at the Fermi level because of the experimental resolution and the 60 meV energy broadening caused by the inhomogeneity of the SPV induced by the pump.
  53. F. Giustino, Electron-phonon interactions from first principles, Rev. Mod. Phys. 89, 015003 (2017).
  54. F. Petocchi, C. W. Nicholson, B. Salzmann, D. Pasquier, O. V. Yazyev, C. Monney, and P. Werner, Mott versus hybridization gap in the low- temperature phase of 1T-TaS2, Phys. Rev. Lett. 129, 016402 (2022), and references therein.
  55. D. R. Baykusheva, H. Jang, A. A. Husain, S. Lee, S. F. R. TenHuisen, P. Zhou, S. Park, H. Kim, J.-K. Kim, H-D. Kim, M. Kim, S.-Y. Park, P. Abbamonte, B. J. Kim, G. D. Gu, Y. Wang, and M. Mitrano, Ultrafast renormalization of the on-site Coulomb repulsion in a cuprate superconductor, Phys. Rev. X 12, 011013 (2022).
  56. T. Lojewski et al., Photoinduced charge transfer renormalization in NiO, Phys. Rev. B 110, 245120 (2024).
  57. Indeed, the low optical absorption coefficient of Si at 800nm−103cm−1- limits the maximum heating of the Si substrate after a pump pulse at about 1 K. The surface layer absorbs less than 0.1% of the photons because the maximum excitation density estimated from the spectra of Fig. 2 is 0.02 per cell and the pump pulse gives 30 photons per surface unit cell. Assuming a surface specific heat comparable to that of bulk Si, this corresponds to a maximum increase in the the surface-lattice temperature of the order of 1 K. If carrier multiplication by impact scattering occurs after photoexcitation, the number of photons initially absorbed by the surface layer would be even smaller than estimated above, implying an even smaller lattice temperature increase.
  58. S. S. Bakshi and P. Majumdar, Distinct charge and spin recovery dynamics in a photo-excited Mott insulator, Phys. Rev. Lett. 133, 256501 (2024).
  59. www.trieste.nffa.eu.
  60. S. Modesti, Data for “Transient photoexcited state of a small-gap quasi-two-dimensional Mott-Hubbard insulator” [Dataset], Zenodo, 2026, https://zenodo.org/records/18510537.

Outline

Information

Phys. Rev. B 114, 125131– Published 25 August, 2026
  • Received 14 February 2026
  • Revised 21 July 2026
  • Accepted 13 August 2026
Crossmark - Check for updates button
Creative Commons Logo

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Published by the American Physical Society

Sign In to Your Journals Account

Filter

Filter

Article Lookup

Enter a citation