Non-reciprocal transport properties in 2D materials

Non-reciprocal transport describes the directional flow of charge, spin, or orbital properties. This phenomenon occurs when the response varies with the direction of an applied “force”, such as an electric or magnetic field. It is typically due to broken symmetries such as time-reversal symmetry (T), inversion symmetry (P), and rotational symmetry. The engineering of symmetries in two dimensional (2D) materials brings novel electronic states which leads to intriguing non-reciprocal transport properties, including nonlinear Hall effect induced by Berry curvature dipole in bilayer WTe₂¹ and by quantum metric in even-layer MnBi₂Te₄^2,3 and superconducting diode effect in various non-centrosymmetric superconductors^4–8. Through the manipulation of spontaneous or artificial symmetry breaking, the interplay between topology, superconductivity, and magnetism, provides unique opportunity to understand the symmetry-driven physics and paves the way for practical application of 2D devices.

The objective of this project is to investigate the nonlinear non-reciprocal transport properties of 2D devices based on novel van der Waals materials. This will equip students with the advanced techniques required to build a field-effect transistor device on 2D materials for the purpose of tuning the symmetry of electronic states by means of electric and magnetic fields. Additionally, the student will gain proficiency in performing transport measurements on 2D devices using a lock-in amplifier technique, such as the electrical second harmonic generation (i.e. sum-frequency generation) method. The selected student will work with Dr. Changjiang Yi from MPI-CPFS and Dr. Nikola Poccia from IFW, specializing in 2D device fabrication and transport properties measurement. It is requested that candidates possess a basic knowledge and skill of charge transport measurement and a background of solid-state physics.