Intervalley scattering and weak localization in Si-based two-dimensional structures

Abstract

We have measured the weak localization magnetoresistance in (001)-oriented Si MOS structures with a wide range of mobilities. For the quantitative analysis of the data, we have extended the theory of weak-localization corrections in the ballistic regime to the system with two equivalent valleys in electron spectrum. This theory describes the observed magnetoresistance and allows the extraction of the phase breaking time τϕ and the intervalley scattering time τv. The temperature dependences τϕ(T ) for all studied structures are in good agreement with the theory of electronelectron interaction effects in two-dimensional systems. The intervalley scattering is elastic and rather strong: τv is typically only an order of magnitude greater than the transport time, τ . It is found that the intervalley scattering rate is temperature-independent and the ratio τv/τ decreases with increasing the electron density. These observations suggest that the roughness of the Si-SiO2 interface plays the major role in intervalley scattering.

Metallic behaviour in SOI quantum wells with strong intervalley scattering

“…We checked that the phase coherence time obtained by fitting the MC with the Hikami formula30 is consistent with that obtained with the equations of Ref. 32 (see Fig. 3).…”

“…Intervalley scattering time can be extracted from the weak localisation magneto-conductivity (MC)3132. At low magnetic field and for strong intervalley scattering, the MC is that of a single valley system since the valleys are mixed at the time scale of the phase coherence time τ φ .…”

“…two times that of a single valley system). We used a recent theory interpolating between these regimes32 to fit the experimental data. The two adjustable parameters were τ ⊥ and τ φ (See supplementary information for the code used).…”

Renormalization group study of a two-valley system with spin splitting

“…They are generalized here to include the effects of ∆ v and ∆ ⊥ in a two-valley system. [It is assumed that ∆ ⊥ < ∆ v , which appears to be the case in high mobility silicon inversion layers 15,16 .] The relevant interaction amplitudes are identified and the corresponding scaling equations are determined in low, ∆ z ∆ ⊥ , and intermediate-fields, The RG equations for finite ∆ v and ∆ ⊥ with ∆ z = 0 are detailed in Ref.…”

Nondiffusion theory of weak localization magnetoresistance in graphene

“…Ref. 14) time inversion guarantees diffusion pole only for intervalley Cooperons which do not contribute to conductivity in the absence of intervalley transitions. For diffusion pole for intravalley Cooperons other symmetries (in graphene space inversion inside one valley 7,9 ) are needed.…”