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Field-induced negative differential spin lifetime in silicon
Jing Li1, Lan Qing, Hanan Dery
1Department of Physics and Center for Nanophysics and Advanced Materials, University of Maryland, College Park, Maryland 20742, USA.
Physical Review Letters
|May 17, 2012
Summary
Electric fields in silicon create thermal differences, altering spin relaxation. This study reveals phonon-assisted scattering enhances spin-flip, causing unexpected spin depolarization and negative spin lifetime.
Area of Science:
- Condensed matter physics
- Materials science
- Spintronics
Background:
- Spin relaxation mechanisms in semiconductors are crucial for spintronic device applications.
- The Elliott-Yafet theory describes spin relaxation due to spin-dependent scattering.
- Electric-field-induced effects on spin dynamics in silicon require further investigation.
Purpose of the Study:
- To investigate the impact of electric-field-induced thermal asymmetry on spin relaxation mechanisms in pure silicon.
- To understand the enhanced spin depolarization observed in long-distance spin transport devices.
- To identify the specific scattering processes responsible for anomalous spin behavior.
Main Methods:
- Experimental measurements using long-distance spin transport devices.
- Detailed Monte Carlo simulations to model spin dynamics.
- Analysis of electron-phonon interactions and scattering between conduction band valleys.
Main Results:
- Electric-field-induced thermal asymmetry significantly alters the dominant spin relaxation mechanism.
- Observed spin depolarization exceeds predictions of the standard Elliott-Yafet theory, even at low temperatures.
- Phonon emission during intervalley scattering between different crystal axes enhances spin-flip rates.
- Anomalous behavior observed: reduced transit time correlates with decreased spin polarization and apparent negative spin lifetime beyond a critical electric field.
Conclusions:
- The interplay between electric fields, thermal asymmetry, and phonon-mediated scattering is critical for understanding spin relaxation in silicon.
- The standard Elliott-Yafet theory is insufficient to explain the observed spin depolarization under these conditions.
- Intervalley scattering involving phonon emission presents a significant spin relaxation pathway, leading to counterintuitive spin dynamics.
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