The Topology of Conductive Ferroelectric Domain Walls

• Applicant: Professor Dr. Lukas M. Eng
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 407435946

• Final Report Year: 2025

Final Report Abstract

Domain walls (DWs) in ferroelectrics have become a topic of major interest over the last 10 years due to their exceptional dielectric, optical, magnetic, electronic and mechanical properties. The DWs represent nanometric interfaces that extend across the full bulk system and display an ultra-high electronic conductivity, reaching several 10 µA for a single DW in bulk single crystalline LiNbO3 (LNO). These remarkable properties propel ferroelectric DWs as one of the most promising func–tional nanostructure for modern-type and reconfigurable applications in nano-electronic devices. According to recent studies, ferroelectric DWs could contain novel topological structures in their dielectric polarization that are much more complex than the Ising-type configuration, which is the traditionally expected DW type in uniaxial ferroelectrics. The local symmetry breaking at the DWs is particularly important as it may promote exotic polar topological structures, similar to those observed in magnetic systems. Exploring the detailed ferroic structure of ferroelectric DWs is a prerequisite for the understanding and control of DW properties. The goal of this joint research project is to elucidate the local symmetry and topology at such DW regions and to investigate and quantify their interrelated physical and optical properties when being rendered highly conductive. The two teams allied within this joint German-French project have shown that DWs can be elegantly tuned for carrying and transporting high electronic currents along the two-dimensional (2D) DW. In LNO; the free charge carrier density within such a wall can be steered by simply varying the DW’s inclination angle with respect to the polar axes. We then expect this DW to convert from its pure Ising-type configuration into a Bloch- or Néel-type state, depending on both the material under investigation, any possible sample doping, or an electrical bias field applied across the crystal. In addition, we have developed sophisticated local probe and nonlinear optical techniques that are able to quantify and 3D map the presence of such non-Ising configurations. We accordingly intend to engineer chiral DWs in the LNO single crystals family, both with and without Mg doping, and monitor their behavior in real time and real space using, for instance, second-harmonic generation polarimetry. This project is expected to deliver groundbreaking insight on the origin and build-up of such non-Ising, possibly chiral polarization structures at DWs, as is necessary for the profound understanding and tuning of future optoelectronic nano-devices based on ferroelectric DWs.

Publications

• Nanostructured Borate Halides for Optical Second Harmonic Generation at Surfaces. European Journal of Inorganic Chemistry, 2020(25), 2465-2469.
  Tan, Deming; Kirbus, Benjamin; Eng, Lukas M. & Ruck, Michael
  
• Poling thin-film x-cut lithium niobate for quasi-phase matching with sub-micrometer periodicity. Journal of Applied Physics, 127(19).
  Zhao, Jie; Rüsing, Michael; Roeper, Matthias; Eng, Lukas M. & Mookherjea, Shayan
  
• Resource‐Efficient Low‐Temperature Synthesis of Microcrystalline Pb2B5O9X (X = Cl, Br) for Surfaces Studies by Optical Second Harmonic Generation. Small, 16(23).
  Tan, Deming; Kirbus, Benjamin; Rüsing, Michael; Pietsch, Tobias; Ruck, Michael & Eng, Lukas M.
  
• Three-Dimensional Optical Analysis of Ferroelectric Domain Walls. Domain Walls, 152-184. Oxford University Press.
  Haußmann, A.; Eng, L. M. & Cherifi-Hertel, S.
  
• Broadband coherent anti-Stokes Raman scattering for crystalline materials. Physical Review B, 104(22).
  Hempel, Franz; Reitzig, Sven; Rüsing, Michael & Eng, Lukas M.
  
• Quantifying the coherent interaction length of second-harmonic microscopy in lithium niobate confined nanostructures. Journal of Applied Physics, 130(13).
  Amber, Zeeshan H.; Kirbus, Benjamin; Eng, Lukas M. & Rüsing, Michael
  
• Quantifying the refractive index of ferroelectric domain walls in periodically poled LiNbO3single crystals by polarization-sensitive optical coherence tomography. Optics Express, 29(21), 33615.
  Golde, Jonas; Rüsing, Michael; Rix, Jan; Eng, Lukas M. & Koch, Edmund
  
• “Seeing Is Believing”—In-Depth Analysis by Co-Imaging of Periodically-Poled X-Cut Lithium Niobate Thin Films. Crystals, 11(3), 288.
  Reitzig, Sven; Rüsing, Michael; Zhao, Jie; Kirbus, Benjamin; Mookherjea, Shayan & Eng, Lukas M.
  
• Brillouin and Raman imaging of domain walls in periodically-poled 5%-MgO:LiNbO3. Optics Express, 30(4), 5051.
  Rix, Jan; Rüsing, Michael; Galli, Roberta; Golde, Jonas; Reitzig, Sven; Eng, Lukas M. & Koch, Edmund
  
• High-speed hyperspectral imaging of ferroelectric domain walls using broadband coherent anti-Stokes Raman scattering. Applied Physics Letters, 120(16).
  Reitzig, Sven; Hempel, Franz; Ratzenberger, Julius; Hegarty, Peter A.; Amber, Zeeshan H.; Buschbeck, Robin; Rüsing, Michael & Eng, Lukas M.
  
• Nanoscale Conductive Sheets in Ferroelectric BaTiO3: Large Hall Electron Mobilities at Head-to-Head Domain Walls. ACS Applied Nano Materials, 5(7), 8717-8722.
  Beccard, Henrik; Kirbus, Benjamin; Beyreuther, Elke; Rüsing, Michael; Bednyakov, Petr; Hlinka, Jiří & Eng, Lukas M.
  
• Nonlinear optical interactions in focused beams and nanosized structures. Journal of Applied Physics, 132(21).
  Amber, Zeeshan H.; Spychala, Kai J.; Eng, Lukas M. & Rüsing, Michael
  
• Tuning domain wall conductivity in bulk lithium niobate by uniaxial stress. Physical Review B, 106(14).
  Singh, Ekta; Beccard, Henrik; Amber, Zeeshan H.; Ratzenberger, Julius; Hicks, Clifford W.; Rüsing, Michael & Eng, Lukas M.
  
• Tuning the Čerenkov second harmonic contrast from ferroelectric domain walls via anomalous dispersion. Journal of Applied Physics, 132(21).
  Hegarty, Peter A.; Eng, Lukas M. & Rüsing, Michael
  
• Turn all the lights off: Bright- and dark-field second-harmonic microscopy to select contrast mechanisms for ferroelectric domain walls. Journal of Applied Physics, 131(24).
  Hegarty, Peter A.; Beccard, Henrik; Eng, Lukas M. & Rüsing, Michael
  
• Hall mobilities and sheet carrier densities in a single LiNbO₃ conductive ferroelectric domain wall. Physical Review Applied, 20(6).
  Beccard, Henrik; Beyreuther, Elke; Kirbus, Benjamin; Seddon, Samuel D.; Rüsing, Michael & Eng, Lukas M.
  
• Impact of 3D Curvature on the Polarization Orientation in Non-Ising Domain Walls. Nano Letters, 23(3), 795-803.
  Acevedo-Salas, Ulises; Croes, Boris; Zhang, Yide; Cregut, Olivier; Dorkenoo, Kokou Dodzi; Kirbus, Benjamin; Singh, Ekta; Beccard, Henrik; Rüsing, Michael; Eng, Lukas M.; Hertel, Riccardo; Eliseev, Eugene A.; Morozovska, Anna N. & Cherifi-Hertel, Salia
  
• Modeling nonlinear optical interactions of focused beams in bulk crystals and thin films: A phenomenological approach. Journal of Applied Physics, 133(12).
  Spychala, Kai J.; Amber, Zeeshan H.; Eng, Lukas M. & Ruesing, Michael
  
• Vibrational properties of LiNbO₃ and LiTaO₃ under uniaxial stress. Physical Review Materials, 7(2).
  Singh, Ekta; Pionteck, Mike N.; Reitzig, Sven; Lange, Michael; Rüsing, Michael; Eng, Lukas M. & Sanna, Simone
  
• Ferroelectric Hysteresis Measurement in the Lithium Niobate‐Lithium Tantalate Single‐Crystalline Family: Prospects for Lithium Niobate‐Tantalate. physica status solidi (a), 222(1).
  Koppitz, Boris; Ganschow, Steffen; Rüsing, Michael & Eng, Lukas M.
  
• Probing ferroelectric phase transitions in barium titanate single crystals via in situ second harmonic generation microscopy. Journal of Applied Physics, 136(15).
  Kirbus, Benjamin; Seddon, Samuel D.; Kiseleva, Iuliia; Beyreuther, Elke; Rüsing, Michael & Eng, Lukas M.
  
• Toward the reproducible fabrication of conductive ferroelectric domain walls into lithium niobate bulk single crystals. Journal of Applied Physics, 136(10).
  Ratzenberger, Julius; Kiseleva, Iuliia; Koppitz, Boris; Beyreuther, Elke; Zahn, Manuel; Gössel, Joshua; Hegarty, Peter A.; Amber, Zeeshan H.; Rüsing, Michael & Eng, Lukas M.