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Register a new userInteraction correction to the conductivity of two-dimensional electron gas in In$_x$Ga$_{1-x}$As/InP quantum well structure with strong spin-orbit coupling
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Added by
Alexander Germanenko
Publication date
2011
fields
Physics
and research's language is
English
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The electron-electron interaction quantum correction to the conductivity of the gated single quantum well InP/In$_{0.53}$Ga$_{0.47}$As heterostructures is investigated experimentally. The analysis of the temperature and magnetic field dependences of the conductivity tensor allows us to obtain reliably the diffusion part of the interaction correction for different values of spin relaxation rate, $1/tau_s$. The surprising result is that the spin relaxation processes do not suppress the interaction correction in the triplet channel and, thus, do not enhance the correction in magnitude contrary to theoretical expectations even in the case of relatively fast spin relaxation, $1/Ttau_ssimeq (20-25)gg 1$.
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We study the electron-electron interaction contribution to the conductivity of two-dimensional In$_{0.2}$Ga$_{0.8}$As electron systems in the diffusion regime over the wide conductivity range, $sigmasimeq(1-150) G_0$, where $G_0=e^2/(2pi^2hbar)$. We show that the data are well described within the framework of the one-loop approximation of the renormalization group (RG) theory when the conductivity is relatively high, $sigma gtrsim 15 G_0$. At lower conductivity, the experimental results are found to be in drastic disagreement with the predictions of this theory. The theory predicts much stronger renormalization of the Landaus Fermi liquid amplitude, which controls the interaction in the triplet channel, than that observed experimentally. A further contradiction is that the experimental value of the interaction contribution does not practically depend on the magnetic field, whereas the RG theory forecasts its strong decrease due to decreasing diagonal component of the conductivity tensor in the growing magnetic field.
The electron-electron interaction quantum correction to the conductivity of the gated double well Al$_x$Ga$_{1-x}$As/GaAs structures is investigated experimentally. The analysis of the temperature and magnetic field dependences of the conductivity tensor allows us to obtain reliably the diffusion part of the interaction correction for the regimes when the structure is balanced and when only one quantum well is occupied. The surprising result is that the interaction correction does not reveal resonant behavior; it is practically the same for both regimes.
In this work we study interacting electrons on square lattice in the presence of strong Rashba spin-orbit interaction. The spin-orbit term forces the time-reversal electron states to be paired in even Cooper channels. For concreteness, we only consider the repulsive onsite Hubbard and nearest-neighbor coulomb interactions, the so called extended Hubbard model. To examine the superconducting instability we obtain the effective interaction between electrons within the random phase approximation and treat the pairing instabilities driven by charge and spin fluctuations and their combined effects. We mapped out the phase diagram of the model in terms of interactions and electron fillings, and found that while the $d_{xy}$ and $d_{x^2-y^2}$ symmetries are the most likely pairing symmetries driven by charge and spin fluctuations, respectively, the strong effect of both fluctuations yields higher angular momentum Cooper instability. The possibility of topological superconductivity and triplet pairing is also discussed.
We study the temperature dependence of the conductivity due to quantum interference processes for a two-dimensional disordered itinerant electron system close to a ferromagnetic quantum critical point. Near the quantum critical point, the cross-over between diffusive and ballistic regimes of quantum interference effects occurs at a temperature $ T^{ast}=1/tau gamma (E_{F}tau)^{2}$, where $gamma $ is the parameter associated with the Landau damping of the spin fluctuations, $tau $ is the impurity scattering time, and $E_{F}$ is the Fermi energy. For a generic choice of parameters, $T^{ast}$ is smaller than the nominal crossover scale $1/tau $. In the ballistic quantum critical regime, the conductivity behaves as $T^{1/3}$.
We use the Hirsch-Fye quantum Monte Carlo method to study the single magnetic impurity problem in a two-dimensional electron gas with Rashba spin-orbit coupling. We calculate the spin susceptibility for various values of spin-orbit coupling, Hubbard interaction, and chemical potential. The Kondo temperatures for different parameters are estimated by fitting the universal curves of spin susceptibility. We find that the Kondo temperature is almost a linear function of Rashba spin-orbit energy when the chemical potential is close to the edge of the conduction band. When the chemical potential is far away from the band edge, the Kondo temperature is independent of the spin-orbit coupling. These results demonstrate that, for single impurity problem in this system, the most important reason to change the Kondo temperature is the divergence of density of states near the band edge, and the divergence is induced by the Rashba spin-orbit coupling.
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