[Paper Review] Spin dephasing in III-V nanowires

Ashish Kumar, Bahniman Ghosh|arXiv (Cornell University)|Jun 23, 2011

Quantum and electron transport phenomena3 references3 citations

TL;DR

This study investigates spin dephasing in InP and InSb nanowires using a semiclassical Monte Carlo approach, analyzing contributions from D'yakonov-Perel (DP) and Elliott-Yafet (EY) mechanisms. InSb exhibits significantly stronger spin dephasing than InP due to enhanced spin-orbit coupling, resulting in shorter spin dephasing lengths and distinct steady-state spin distributions, highlighting material-dependent spin transport limitations in III-V nanowires.

ABSTRACT

We use semiclassical Monte Carlo approach to investigate spin polarized transport in InP and InSb nanowires. Spin dephasing in III-V channels is caused due to D'yakonov- Perel (DP) relaxation and due to Elliott-Yafet (EY) relaxation. The DP relaxation occurs because of bulk inversion asymmetry (Dresselhaus spin-orbit interaction) and structural inversion asymmetry (Rashba spin-orbit interaction). The injection polarization direction studied is that along the length of the channel. The dephasing rate is found to be very strong for InSb as compared to InP which has larger spin dephasing lengths. The ensemble averaged spin components vary differently for both InP and InSb nanowires. The steady state spin distribution also shows a difference between the two III-V nanowires.

Motivation & Objective

• To understand the mechanisms of spin dephasing in III-V nanowires, particularly in InP and InSb.
• To compare the relative contributions of D'yakonov-Perel (DP) and Elliott-Yafet (EY) spin relaxation mechanisms in these materials.
• To investigate how spin polarization evolves along the nanowire channel under steady-state transport conditions.
• To quantify differences in spin dephasing lengths and spin component decay between InP and InSb nanowires.
• To evaluate the impact of structural and bulk inversion asymmetry on spin transport properties.

Proposed method

• A semiclassical Monte Carlo simulation framework is employed to model spin-polarized electron transport in InP and InSb nanowires.
• The model incorporates both D'yakonov-Perel (DP) relaxation due to spin-orbit coupling from bulk and structural inversion asymmetry.
• Elliott-Yafet (EY) relaxation is included to account for spin-flip scattering due to electron-impurity and electron-phonon interactions.
• The simulation tracks the evolution of ensemble-averaged spin components over time and along the nanowire length.
• The injection polarization is aligned along the channel direction to assess dephasing dynamics in the transport direction.
• Steady-state spin distributions are computed and compared between InP and InSb to assess material-dependent spin coherence.

Experimental results

Research questions

• RQ1 How do D'yakonov-Perel and Elliott-Yafet mechanisms contribute to spin dephasing in InP and InSb nanowires?
• RQ2 What is the relative strength of spin dephasing in InSb compared to InP under identical transport conditions?
• RQ3 How do the ensemble-averaged spin components evolve differently in InP and InSb nanowires?
• RQ4 What are the steady-state spin distribution profiles in InP and InSb nanowires?
• RQ5 How does the spin dephasing length differ between InP and InSb due to varying spin-orbit coupling strengths?

Key findings

• InSb exhibits significantly stronger spin dephasing than InP due to enhanced spin-orbit coupling, particularly from the Rashba and Dresselhaus mechanisms.
• The spin dephasing rate is markedly higher in InSb, leading to shorter spin dephasing lengths compared to InP.
• Ensemble-averaged spin components decay more rapidly in InSb than in InP, indicating faster loss of spin polarization.
• Steady-state spin distributions differ qualitatively between InP and InSb, with InSb showing stronger spatial decay of spin polarization.
• The combined effects of structural and bulk inversion asymmetry lead to dominant DP relaxation in both materials, but with stronger impact in InSb.
• The study confirms that material choice (InSb vs. InP) critically influences spin coherence in III-V nanowire-based spintronic devices.