m.m. asmar & s.e. ulloa ohio university. outline motivation. the studied system and the...
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Spin-Dependent Scattering From Gated Obstacles in Graphene
Systems M.M. Asmar & S.E. Ulloa
Ohio University
Outline Motivation.
The studied system and the mathematical approach.
Results and analysis.
Conclusions.
Because of the high importance of spintronics on which the spin orbit interactions play a basic role, we study and compare the relaxation times in the presence of a gated potential to the relaxation times in the presence of SOI in graphene systems.
The importance of the relaxation times is based on their proportionality to the conductance of the system.
Motivation
Wave functions (at K point) are :
, and
From the analytical form of the wave function we can extract some information such as
Phase shifts Differential cross sections Total cross sections Transport cross section which is inversely proportional to the relaxation time Conductance, which is proportional to the relaxation time
Total angular momentum
• C. L. Kane and E. J. Mele, PRL 95, 226801 (2005).
m
Results and Analysis In the presence of a gated obstacle and no SOI
Ramsauer-Townsend Effect
at V/2
•J. Milton Pereira, Jr., V. Mlinar, and F. M. Peeter, P RB 74, 045424 (2006)
In the presence gated obstacles and Intrinsic SOI
• C. L. Kane and E. J. Mele, PRL 95, 226801 (2005).• Daniel Huertas-Hernando, F. Guinea,and Arne Brataas1, PRB 74,
155426 (2006).
In the presence of the gated obstacle and Rashba SOI
Comparable relaxation times
• Gierz, et al., arXiv:1004.1573.• J. Sánchez-Barriga, et al. , Diamond & Related Materials 19
(2010) 734–74
Longer spin flip relaxation times
• A.H. Castro Neto and F. Guinea, PRL 103, 026804 (2009).• N. Tombros et al., Nature (London) 448, 571 (2007).
ConclusionsQuasi bound states reflect themselves as
resonances in the cross section.Intrinsic SO decreases the scattering time and
shifts the resonances in the cross section.Spin flip relaxation times are much longer that
the momentum relaxation times at low energies.
Momentum and spin-flip scattering times are comparable at relatively high energies.
Spin flip times and momentum relaxation times are equal at both the K and K’ point.