1 / 12

Long-lived electron spins in a modulation doped (100) GaAs quantum well

Long-lived electron spins in a modulation doped (100) GaAs quantum well. John S. Colton Brigham Young University. Students: (grad) Tyler Park (undergrads) Ken Clark David Meyer Daniel Craft Phil White Jane Cutler . Sample: Allan Bracker, NRL.

Download Presentation

Long-lived electron spins in a modulation doped (100) GaAs quantum well

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Long-lived electron spins in a modulation doped (100) GaAs quantum well John S. Colton Brigham Young University Students: (grad)Tyler Park (undergrads) Ken Clark David Meyer Daniel Craft Phil White Jane Cutler Sample: Allan Bracker, NRL Talk for APS March Meeting Mar 21, 2013 Ref: J. Appl. Phys. 112, 084307 (2012)

  2. Importance of spin lifetimes • DiVincenzo criteria, 1998 • Kikkawa & Awschalom, long lifetimes in GaAs, 1998 • Greilich et al., Mode locking, 2006 • Balocchi et al., Electrical control of lifetimes, 2011 • Connections • Implementations—spin control • Theory—understanding spin

  3. QW sample (Bracker, NRL) GaAs wells Time-resolved Kerr rotation (cw laser) 2.8 nm well 4.2 nm well AlGaAs barriers Tischler et al, Phys Rev B 66, 081310R (2002) 6.2 nm well 8.4 nm well 14 nm well GaAs substrate Solid State Comm. 152, 410 (2012)

  4. What do we expect? • Lack of bulk inversion symmetry  spin splitting of CB (“DP”) • D’yakonov and Kachorovskii (1986), QWs • Bastard & Ferreira (1992), ionized impurity scattering • ts = 2.5 ns for 15 nm well at 10 K • perhaps 10-100 longer at 1.5 K • Bastard (1992), high fields (6-15 T) • ts = 1-2 ns for 9 nm well, ~B1/2 • Terauchi et al (1999), 300 K, DK verified in part • Lau (2001, 2002), 100+ K • matched experiments of Terauchi, and Kikkawa & Awschalom • also T2 T1 • Various T2* measurements: a few ns in GaAs, longer in II-VI • Longest lifetimes in any QWs: ~35 ns

  5. Doped QWs: Selection Rules • Singlet trion: e + e + h(either  or , either hh or lh)

  6. LH HH Wavelength Summary Peak positions:

  7. Spin Decays! pump and probe overlapped 5 K ts = 169 ns ts = 85 ns

  8. Spin Lifetimes, Summary • Very long lifetimes!! • Lifetimes increase monotonically with B (one exception), but not B1/2 dependence ts > 1000 ns!

  9. Dynamic Nuclear Polarization, and removal • Fields of 4T and higher polarization “pinned” polarization removed

  10. Selection Rules and Wavelength Dependence • Singlet trion: e + e + h(either  or , either hh or lh) What about exciton? (II-VI: probes delocalized electron spins) HH exciton?

  11. Evidence of Two Spin Populations? Compare: II-VI QWs • Localized vs. Delocalized localized? l1 “LHT” l2 delocalized? Zhukov et al, PRB 2007 (see also Hoffman et al, PRB 2006)

  12. Conclusions • QW lifetimes via pump-probe • T1 lifetimes far longer than seen before… >1000 ns! • Previously in QWs, 35 ns max! • Not too far from Bastard & Ferreira theory (impurity-related scattering) • Probably also very long T2 lifetime! • Saw DNP, suppressed with NMR • Saw evidence of two spin populations • localized vs. delocalized • seen by others in II-VI QWs Reference: Colton et al., J. Appl. Phys. 112, 084307 (2012)

More Related