Quantum transport in Rashba spin-orbit materials: A review (1502.00570v3)

Abstract: In this review article we describe spin-dependent transport in materials with spin-orbit interaction of Rashba type. We mainly focus on semiconductor heterostructures, topological insulators, graphene and hybrid structures involving superconductors as well. We start from basic properties of Rashba Hamiltonian in a two dimensional electron gas and then describe transport properties in two- and quasi-one-dimensional systems. The problem of spin current generation and interference effects in mesoscopic devices is described in detail. We address also the role of Rashba interaction on localisation effects in lattices with nontrivial topology, as well as on the Ahronov-Casher effect in ring structures. A brief section, in the end, describes also some related topics including the spin-Hall effect, the transition from weak localisation to weak anti localisation and the physics of Majorana Fermions in hybrid heterostructures involving Rashba materials in the presence of superconductivity.

Quantum Transport in Rashba Spin-Orbit Materials

In "Quantum transport in Rashba spin-orbit materials: A review", Bercioux and Lucignano provide a comprehensive examination of spin-dependent transport mechanisms in materials exhibiting Rashba spin-orbit interaction (RSOI), focusing on semiconductor heterostructures, with additional considerations given to topological insulators, graphene, and systems involving superconductors.

Overview of Rashba Spin-Orbit Interaction

The Rashba spin-orbit interaction, originating from structural inversion asymmetry within semiconductor heterostructures, influences the transport properties of materials by coupling the electron’s spin with its momentum. The authors begin by describing the Rashba Hamiltonian formulated in a two-dimensional electron gas (2DEG) and extend their discussion to transport characteristics in more confined systems, such as quasi-one-dimensional quantum wires.

Key Topics

1. Rashba Hamiltonian and Transport Characteristics: By detailing the Rashba Hamiltonian, the paper elucidates how electron spin couples to momentum, leading to spin-momentum locking and causing unique interference patterns in mesoscopic devices.
2. Spin Current Generation: This section of the paper includes derivations of pure spin current in semiconductor systems, addressing mechanisms like the ratchet and the pumping effect, which leverage the Rashba interaction to modulate transport without accompanying charge currents.
3. Interference and Berry Phase: The authors delve into interference effects induced by Rashba interaction, particularly focusing on the Aharonov-Casher effect and non-Abelian gauge fields, which can profoundly affect quantum networks and rings.
4. Applications in Quantum Devices: The paper examines the principles underlying spintronic devices such as the Datta-Das spin-field-effect transistor, illustrating the modulation of spin-polarized currents through electrostatic gating.
5. Related Phenomena and Novel Developments: Included are discussions of weak anti-localization effects in diffusive systems, brought about by Rashba interaction, and its role in promising Majorana fermion-based quantum device applications.

Strong Numerical Results and Implications

The paper draws attention to conditions enabling weak anti-localization, as evidenced by changes in magnetoconductance patterns. It highlights quantitative relationships between Rashba coupling strength and observable transport behaviors in quantum wires and rings. These results imply potential practical developments in spintronic technology through refinement of material design and coupling modulation.

Future Directions

Bercioux and Lucignano speculate on future trends, suggesting that continued exploration in this area might yield advanced spintronic devices for quantum computing, with Rashba systems offering a pathway towards robust, tunable qubits. Furthermore, integration with superconducting systems could expand the functionality and discovery of new quantum states.

This review paper offers substantial insights into the transport properties of Rashba spin-orbit materials and sets a baseline for ongoing theoretical and experimental exploration in spintronics and quantum information sciences. For researchers in the field, it serves as a critical reference, capturing the dynamic interplay of spin-orbit effects with quantum transport properties.