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Terahertz carrier dynamics in SrTiO3/LaTiO3 interfacial two-dimensional electron gases

Ahana Bhattacharya1, Andri Darmawan1,2, Jeong Woo Han1,3, Frederik Steinkamp1, Nicholas S. Bingham4,5,6, Ryan J. Suess1, Stephan Winnerl7, Markus E. Gruner1,2, Eric N. Jin6 et al.

Frederick J. Walker6, Charles H. Ahn6, Rossitza Pentcheva1,2, and Martin Mittendorff1,2,*

  • *Contact author: martin.mittendorff@uni-due.de
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Phys. Rev. B 112, 155307 – Published 27 October, 2025

DOI: https://doi.org/10.1103/g23p-b4m5

Abstract

A two-dimensional electron gas (2DEG) forms at the interface of complex oxides like SrTiO3 (STO) and LaTiO3 (LTO), despite each material having a low native conductivity, as a band and a Mott insulator, respectively. The interface 2DEG hosts charge carriers with moderate charge carrier density and mobility that raised interest as a material system for applications like field-effect transistors or detectors. Of particular interest is the integration of these oxide systems in silicon technology. To this end we study the carrier dynamics in a STO/LTO/STO heterostructure epitaxially grown on Si(001) both experimentally and theoretically. Linear THz spectroscopy was performed to analyze the temperature dependent charge carrier density and mobility, which was found to be in the range of 1012cm−2 and 1000 cm2V−1s−1, respectively. Pump-probe measurements revealed a very minor optical nonlinearity caused by hot carriers with a relaxation time of several 10 ps, even at low temperature. Density functional theory calculations with a Hubbard U term on ultrathin STO-capped LTO films on STO/Si(001) show an effective mass of 0.64–0.68 me.

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References (34)

  1. J. Mannhart and D. G. Schlom, Oxide interfaces – an opportunity for electronics, Science 327, 1607 (2010).
  2. H. Y. Hwang, Y. Iwasa, M. Kawasaki, B. Keimer, N. Nagaosa, and Y. Tokura, Emergent phenomena at oxide interfaces, Nat. Mater. 11, 103 (2012).
  3. S. Stemmer and S. J. Allen, Two-dimensional electron gases at complex oxide interfaces, Annu. Rev. Mater. Res. 44, 151 (2014).
  4. Y.-Y. Pai, A. Tylan-Tyler, P. Irvin, and J. Levy, Physics of SrTiO3-based heterostrcutures and nanostructures: A review, Rep. Prog. Phys. 81, 036503 (2018).
  5. M. Yang, J. Zhou Ariando, T. C. Asmara, P. Krüger, X. J. Yu, X. Wang, C. Sanchez-Hanke, Y. P. Feng, T. Venkatesan, and A. Rusydi, Direct observation of room-temperature stable magnetism in LaAlO3/SrTiO3 heterostructures, ACS Appl. Mater. Interfaces 10, 9774 (2018).
  6. A. Ohtomo and H. Y. Hwang, A high-mobility electron gas at the LaAlO3/SrTiO3 heterointerface, Nature (London) 427, 423 (2004).
  7. K. Yang, S. Nazir, M. Behtash, and J. Cheng, High-throughput design of two-dimensional electron gas systems based on polar/nonpolar perovskite oxide heterostructures, Sci. Rep. 6, 34667 (2016).
  8. C. W. Schneider, S. Thiel, G. Hammerl, C. Richter, and J. Mannhart, Microlithography of electron gases formed at interfaces in oxide heterostructures, Appl. Phys. Lett. 89, 122101 (2006).
  9. C. Cen, S. Thiel, J. Mannhart, and J. Levy, Oxide nanoelectronics on demand, Science 323, 1026 (2009).
  10. D. F. Bogorin, C. W. Bark, H. W. Jang, C. Cen, C. M. Folkman, C.-B. Eom, and J. Levy, Nanoscale rectification at the LaAlO3/SrTiO3 interface, Appl. Phys. Lett. 97, 013102 (2010).
  11. P. D. Eerkes, W. G. van der Wiel, and H. Hilgenkamp, Modulation of conductance and superconductivity by top-gating in LaAlO3/SrTiO3 2-dimensional electron system, Appl. Phys. Lett. 103, 201603 (2013).
  12. E. N. Jin, A. Kakekhani, S. Ismail-Beigi, C. H. Ahn, and F. J. Walker, Two-dimensional electron gas oxide remote doping of Si(001), Phys. Rev. Mater. 2, 115001 (2018).
  13. A. Dubroka, M. Rössle, K. W. Kim, V. K. Malik, L. Schlutz, S. Thiel, C. W. Schneider, J. Mannhart, G. Herranz, O. Copie, M. Bibes, A. Barthelemy, and C. Bernhard, Dynamical response and confinement of the electrons at the LaAlO3/SrTiO3 interface, Phys. Rev. Lett. 104, 156807 (2010).
  14. X. Liu, J. Zhang, Z. Zhang, X. Lin, Y. Yu, X. Xing, Z. Jin, Z. Cheng, and G. Ma, Thermodynamics of quasi-2D electron gas at BFO/Si interface probed with THz time-domain spectroscopy, Appl. Phys. Lett. 111, 152906 (2017).
  15. S. Mitra, L. Avazpour, and I. Knezevic, Terahertz conductivity of two-dimensional materials: A review, J. Phys.: Condens. Matter 37, 133005 (2025).
  16. T. Dong, S.-J. Zhang, and N.-L. Wang, Recent development of ultrafast optical characterizations for quantum materials, Adv. Mater. 35, 2110068 (2023).
  17. P. D. C. King, S. McKeown Walker, A. Tamai, A. ke la Torre, T. Eknapakul, P. Buaphet, S.-K. Mo, W. Meevasana, M. S. Bahramy, and F. Baumberger, Quasiparticle dynamics and spin-orbital texture of the SrTiO3 two-dimensional electron gas, Nat. Commun. 5, 3414 (2014).
  18. J. Lloyd-Hughes and T.-I. Jeon, A review of the terahertz conductivity of bulk and nano-materials, J. Infrared Milli. Terahz. Waves 33, 871 (2012).
  19. D. Nuzhnyy, J. Petzelt, S. Kamba, T. Yamada, M. Tyunina, A. K. Tagantsev, J. Levoska, and N. Setter, Polar phonons in some compressively stressed epitaxial and polycrystalline SrTiO3 thin films, J. Electroceram. 22, 297 (2009).
  20. M. Helm, S. Winnerl, A. Pashkin, J. M. Klopf, J.-C. Deinert, S. Kovalev, P. Evtushenko, U. Lehnert, R. Xiang, A. Arnold, A. Wagner, S. M. Schmidt, U. Schramm, T. Cowan, and P. Michel, The ELBE infrared and THz facility at Helmholtz-Zentrum Dresden-Rossendorf, Eur. Phys. J. Plus 138, 158 (2023).
  21. G. Kresse and J. Hafner, Ab initio molecular dynamics for liquid metals, Phys. Rev. B 47, 558 (1993).
  22. G. Kresse and J. Furthmüller, Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set, Comput. Mater. Sci. 6, 15 (1996).
  23. G. Kresse and J. Furthmüller, Efficient iterative schemes for ab initio total-energy calculations using a plane wave basis set, Phys. Rev. B 54, 11169 (1996).
  24. P. E. Blöchl, Projector augmented-wave method, Phys. Rev. B 50, 17953 (1994).
  25. G. Kresse and D. Joubert, From ultrasoft pseudopotentials to the projector augmented-wave method, Phys. Rev. B 59, 1758 (1999).
  26. P. Perdew, K. Burke, and M. Ernzerhof, Generalized gradient approximation made simple, Phys. Rev. Lett. 77, 3865 (1996).
  27. S. L. Dudarev, G. A. Botton, S. Y. Savrasov, C. J. Humphreys, and A. P. Sutton, Electron-energy-loss spectra and the structural stability of nickel oxide: An LADA+ U study, Phys. Rev. B 57, 1505 (1998).
  28. S. Okamoto, A. J. Millis, and N. A. Spaldin, Lattice relaxation in oxide heterostructures: LaTiO3/SrTiO3 superlattices, Phys. Rev. Lett. 97, 056802 (2006).
  29. D. Doennig, W. E. Pickett, and R. Pentcheva, Massive symmetry breaking in LaAlO3/SrTiO3(111) quantum Wells: A three-orbital strongly correlated generalization of graphene, Phys. Rev. Lett. 111, 126804 (2013).
  30. A. M. Kolpak, F. J. Walker, J. W. Reiner, Y. Segal, D. Su, M. S. Sawicki, C. C. Braodbridge, Z. Zhang, Y. Zhu, C. H. Ahn, and S. Ismail-Beigi, Interface-induced polarization and inhibition of ferroelectricity in epitaxial SrTiO3/Si, Phys. Rev. Lett. 105, 217601 (2010).
  31. T. Chen, K. Ahmadi-Majlan, Z. H. Lim, Z. Zhang, J. H. Ngai, and D. P. Kumah, Effect of buffer termination on intermixing and conductivity in LaTiO3/SrTiO3 heterostructures integrated on Si(110), J. Vac. Sci. Technol. A 40, 013206 (2022).
  32. M. J. Veit, R. Arras, B. J. Ramshaw, R. Pentcheva, and Y. Suzuki, Nonzero Berry phase in quantum oscillations from giant Rashba-type spin splitting in LaTiO3/SrTiO3 heterostructures, Nat. Commun. 9, 1458 (2018).
  33. J. R. Danielson, Y.-S. Lee, J. P. Prineas, J. T. Steiner, M. Kira, and S. W. Koch, Interaction of strong single-cycle terahertz pulses with semiconductor quantum wells, Phys. Rev. Lett. 99, 237401 (2007).
  34. D. Sabbagh, J. Schmidt, S. Winnerl, M. Helm, L. Di Gaspare, M. De Seta, M. Virgilio, and M. Ortolani, Electron dynamics in silicon-germanium terahertz quantum fountain structures, ACS Photonics 3, 403 (2016).

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Phys. Rev. B 112, 155307– Published 27 October, 2025
  • Received 28 March 2025
  • Revised 2 October 2025
  • Accepted 6 October 2025
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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.

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