Spin-Orbit Coupling Effects in Two-Dimensional Electron Systems

Spin–orbit coupling (SOC) in two-dimensional electron systems arises when the motion of electrons in a plane interacts with their intrinsic spin, often due to broken inversion symmetry at interfaces or within layered crystals. This interaction lifts spin degeneracy through momentum-dependent splitting of energy bands, most notably via the Rashba effect. In systems such as quantum wells, oxide interfaces and van der Waals heterostructures, SOC gives rise to spin–momentum locking, enabling efficient conversion between charge and spin currents. Consequences include the Edelstein and inverse Edelstein effects, spin–orbit torques that can switch magnetic layers, and emergent topological phases in materials such as two-dimensional topological insulators. Experimental realisations employ transport measurements, spin pumping, optical detection and superconducting interferometry to characterise spin polarisation, torque efficiencies and interfacial spin dynamics. Such phenomena underpin advances in low-power spintronic devices, non-volatile memory and quantum information platforms.

Research from Nature Portfolio

Recent studies have demonstrated direct detection of non-equilibrium spin density at a Rashba interface by embedding the two-dimensional electron system within a planar Josephson junction. Asymmetric interference patterns in superconducting electrodes reveal an additional phase bias induced by the Rashba–Edelstein spin moment, opening routes to magnetic-field-controlled phase devices in superconducting quantum circuits.

A seminal investigation of spin-to-charge conversion at a bismuth–silver interface has provided unambiguous evidence of large charge currents generated by spin pumping into Rashba-split surface states. This work established the potential of interfacial SOC for efficient charge–spin interconversion and set benchmarks for future spintronic architectures based on two-dimensional interfaces.

Research from all publishers

Thin films of the topological insulator Sb₂Te₃ deposited by industrial magnetron sputtering on conventional substrates have exhibited sizeable spin-charge interconversion voltages attributable to surface-state SOC, demonstrating scalable fabrication of spin–orbit readout devices for spin-logic circuits.

Optical measurements in sputter-deposited bismuth films have separated spin–orbit torques from Oersted fields, revealing a giant damping-like torque efficiency of +0.5 and a field-like component of –0.1. Analysis indicates contributions from both bulk spin Hall and interfacial Rashba–Edelstein mechanisms in two-dimensional Bi layers.

At room temperature, graphene/WS₂ heterostructures have shown enhanced spin-to-charge conversion via the inverse Rashba–Edelstein effect at the van der Waals interface. Core-hole clock dynamics and density functional theory reveal Rashba spin splitting of graphene orbitals and strong graphene–WS₂ coupling, informing the design of efficient two-dimensional spintronic interfaces.

Spin-Orbit Coupling Effects in Two-Dimensional Electron Systems publication trend

The graph below shows the total number of articles in spin-orbit coupling effects in two-dimensional electron systems across all publications each year (not limited to Nature Index journals).

Technical terms

Spin–orbit coupling: Interaction between an electron’s spin and its orbital motion, leading to spin-dependent energy band splitting.

Rashba effect: Momentum-dependent splitting of spin bands in a two-dimensional system with structural inversion asymmetry.

Edelstein effect: Generation of non-equilibrium spin density from a charge current in a system with spin–momentum locking.

Inverse Edelstein effect: Conversion of a spin current or spin accumulation into a transverse charge current at an interface.

Spin–momentum locking: Fixed relationship between an electron’s momentum and spin orientation in certain two-dimensional or topological states.

Topological insulator: Material with an insulating bulk and conducting surface or edge states protected by time-reversal symmetry, exhibiting spin–momentum locking.

Two-dimensional electron gas (2DEG): Confined electron system at an interface or within a quantum well, where motion is restricted to a plane.

Spin–orbit torque: Torque exerted on a magnetic moment by spin currents generated via spin–orbit coupling in adjacent layers or surfaces.

References

1. Phase biasing of a Josephson junction using Rashba–Edelstein effect. Nature Communications (2023).
2. Spin‐Orbit Readout Using Thin Films of Topological Insulator Sb2Te3 Deposited by Industrial Magnetron Sputtering. Advanced Functional Materials (2023).
3. Giant Spin‐Orbit Torque in Sputter‐Deposited Bi Films. Advanced Science (2023).
4. Unraveling the Spin-to-Charge Current Conversion Mechanism and Charge Transfer Dynamics at the Interface of Graphene/WS2 Heterostructures at Room Temperature. ACS Applied Materials & Interfaces (2024).