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Register a new userElectron transport through antidot superlattices in $Si/SiGe$ heterostructures: new magnetoresistance resonances in lattices with large diameter antidots
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Added by
Vincent Thomas Francois Renard
Publication date
2006
fields
Physics
and research's language is
English
Authors
E. B. Olshanetsky
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In the present work we have investigated the transport properties in a number of Si/SiGe samples with square antidot lattices of different periods. In samples with lattice periods equal to 700 nm and 850 nm we have observed the conventional low-field commensurability magnetoresistance peaks consistent with the previous observations in GaAs/AlGaAs and Si/SiGe samples with antidot lattices. In samples with a 600 nm lattice period a new series of well-developed magnetoresistance oscillations has been found beyond the last commensurability peak which are supposed to originate from periodic skipping orbits encircling an antidot with a particular number of bounds.
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The valley degree of freedom presents challenges and opportunities for silicon spin qubits. An important consideration for singlet-triplet states is the presence of two distinct triplets, comprised of valley vs. orbital excitations. Here we show that both of these triplets are present in the typical operating regime, but that only the valley-excited triplet offers intrinsic protection against charge noise. We further show that this protection arises naturally in dots with stronger confinement. These results reveal an inherent advantage for silicon-based multi-electron qubits.
We report the results of an experimental study of the magnetoresistance $rho_{xx}$ in two samples of $p$-Si/SiGe/Si with low carrier concentrations $p$=8.2$times10^{10}$ cm$^{-2}$ and $p$=2$times10^{11}$ cm$^{-2}$. The research was performed in the temperature range of 0.3-2 K in the magnetic fields of up to 18 T, parallel to the two-dimensional (2D) channel plane at two orientations of the in-plane magnetic field $B_{parallel}$ against the current $I$: $B_{parallel} perp I$ and $B_{parallel} parallel I$. In the sample with the lowest density in the magnetic field range of 0-7.2 T the temperature dependence of $rho_{xx}$ demonstrates the metallic characteristics ($d rho_{xx}/dT>$0). However, at $B_{parallel}$ =7.2 T the derivative $d rho_{xx}/dT$ reverses the sign. Moreover, the resistance depends on the current orientation with respect to the in-plane magnetic field. At $B_{parallel} cong$ 13 T there is a transition from the dependence $ln(Deltarho_{xx} / rho_{0})propto B_{parallel}^2$ to the dependence $ln(Deltarho_{xx} / rho_{0})propto B_{parallel}$. The observed effects can be explained by the influence of the in-plane magnetic field on the orbital motion of the charge carriers in the quasi-2D system.
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