Measurement by antilocalization of interactions between InAs surface electrons and magnetic surface species

Quantum interference measurement of spin interactions in a bio-organic/semiconductor device structure

“…1b ), as the iron-free species. Comparative quantum interference experiments 19 involving PP-IX, hemin, and solvent only, are performed to assess the influence of the iron center. The InAs surface is patterned with serpentine mesas ( Fig.…”

“…Under SOI a closed diffusive path is accompanied by a spin rotation of 2π, resulting in a change of sign of the wavefunction, destructive interference, reduced backscattering and hence decreased resistance (antilocalization, AL) 16 . AL thus originates in spin-dependent interference of electrons and is sensitive to spin decoherence 1 16 17 18 19 . The spin decoherence of the surface electrons in turn is a sensitive gauge of their spin interactions with magnetic impurities, exceeding direct magnetic measurements in sensitivity 20 and capable of quantifying spin interactions in our low-dimensional spin system.…”

“…Parallels with magnetic resonance methods (EPR and NMR) can be found in the method of characterizing the local spin environment by measuring the spin decoherence time (a T 2 time). In AL, a magnetic field B applied normally to the 2DES breaks the time reversal symmetry and reduces the interference effect, leading to a characteristic magnetoresistance (MR) 1 17 18 19 determined by four characteristic decoherence or scattering rates 1 19 21 . The scattering rates (inverse scattering times) are the elastic scattering rate τ 0 −1 as independently deduced from the areal electron density n s and from the electron mobility, the inelastic scattering rate τ i −1 , the SOI scattering rate τ SO −1 , and the magnetic spin-flip scattering rate τ s −1 .…”

“…The total electron decoherence rate, τ φ −1 , is obtained as τ φ −1 = τ i −1 + 2 τ s −1 . The spin-flip rate τ s −1 is here of particular value because it conveys information about the interactions between the surface hemin and the 2DES 1 19 . The experiments measure the longitudinal resistance R ( B ), with data presented as MR, Δ R ( B ) = R ( B ) − R ( B = 0) normalized to R 0 = R ( B = 0).…”

“…This work uses the expression for Δ σ 2 ( B ) of Ref. 18 modified for the presence of spin-flip scattering 19 : where F ( x ) = Ψ(1/2 + x ) − ln( x ), Ψ is the digamma function, and each scattering time τ α (with α = 0, i, so, s ) enters via a characteristic magnetic field , with D the two-dimensional diffusion coefficient. A numerical fit of Δ R ( B )/ R 0 to equation (1) allows for the extraction of the unknown scattering rates.…”