Violation of Local Reciprocity in Charge-Orbital Interconversion

Area of Science:

• Condensed matter physics
• Spintronics
• Quantum materials

Background:

• Charge and orbital currents are fundamental to modern electronics.
• Understanding their interconversion is key to novel device functionalities.
• Local reciprocity is a cornerstone principle in many physical phenomena.

Purpose of the Study:

• To investigate the local reciprocity in charge-orbital current interconversion.
• To experimentally verify theoretical predictions of nonreciprocity.
• To explore the fundamental mechanisms of orbital-current-driven phenomena.

Main Methods:

• Fabrication and characterization of W/Ni bilayers.
• Measurement of orbital torque (direct process).
• Measurement of orbital pumping (inverse process).

Main Results:

• Demonstrated a violation of local reciprocity in charge-orbital interconversion.
• Observed opposite signs for direct (positive) and inverse (negative) orbital Hall effects in tungsten (W).
• Experimental results align with theoretical predictions of local nonreciprocity.

Conclusions:

• Charge-orbital coupled transport exhibits unique nonreciprocal characteristics.
• Provides direct evidence for local nonreciprocity in W/Ni systems.
• Offers fundamental insights into orbital-current-driven phenomena for future spintronic applications.