All Optical NMR by 2DEG in GaAs/AlGaAs (110) Quantum Well



Conduction electrons are used to optically polarize, detect, and manipulate nuclear spin in a (110) GaAs/AlGaAs quantum well. Using optical Larmor magnetometry, we find that nuclear spin can be polarized along or against the applied magnetic field, depending on field polarity and tilting of the sample with respect to the optical pump beam. Periodic optical excitation of the quantum-confined electron spin reveals a complete spectrum of optically induced and quadrupolar-split nuclear resonances, as well as evidence for Dm = 2 transitions.




Figure 1 (a) Measured Faraday rotation vs Δt taken α= 10 degree and T = 5 K for B =-6, 0, and 6 T, after 10 min exposure to pump and probe beams. (b) Larmor frequency ωL extracted from fits to data as in (a), as a function of  αat B =-6 T and 6 T. Grey-scale plots of FR vs Δt and B for α=10 degree  (c) and α=0 degree (d) show the field asymmetry at nonzero angles. For both angles, the Larmor frequency does no increase linearly with B.


 


Figure 2 (a) ωL as a function of T for different average pump intensities (1.2, 0.37, and 0.12 mW) for B = 6 and -6 T, showing decrease of field asymmetry with higher T and lower pump intensity. The low-intensity data is used to extract |g|. (b) Dependence of nuclear field Bn =ħ ωL/|g|mB- |B| on B and T. Bn is aligned (antialigned) with B at B > 0 (B <-2 T).


 

 


Figure 3 All optical NMR: Measured FR at Δt = 450 ps for α = 5 degee




Figure 4 (a) FR at Δt = 12.86 ns for low fields shows structures which depend on the pump chopper frequency (3 and 6 kHz). (b) A grey-scale plot of the differential FR as a function of B and the chopper frequency shows various resonances at fields proportional to the chopper frequency.



                          Related publications:

1.  Y. Ohno, R. Terauchi, T. Adachi, F. Matsukura, and H. Ohno, Physical Review Letters 83, 4196 (1999).

2.  G. Salis, D.T. Fuchs, J.M. Kikkawa, D.D. Awschalom, Y. Ohno, and H. Ohno, Physical Review Letters 86, 2677 (2001).

3.  G. Salis, D.D. Awschalom, Y. Ohno, and H. Ohno, Physical Review B 64, 195304 (2001).