Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userDisorder and temperature renormalization of interaction contribution to the conductivity in two-dimensional In$_{x}$Ga$_{1-x}$As electron systems
151
0
0.0
(
0
)
Added by
Alexander Germanenko
Publication date
2009
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
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.
rate research
Read More
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, $1/Ttau_ssimeq (20-25)gg 1$.
We consider the effect of quenched spatial disorder on systems of interacting, pinned non-Abelian anyons as might arise in disordered Hall samples at filling fractions u=5/2 or u=12/5. In one spatial dimension, such disordered anyon models have previously been shown to exhibit a hierarchy of infinite randomness phases. Here, we address systems in two spatial dimensions and report on the behavior of Ising and Fibonacci anyons under the numerical strong-disorder renormalization group (SDRG). In order to manage the topology-dependent interactions generated during the flow, we introduce a planar approximation to the SDRG treatment. We characterize this planar approximation by studying the flow of disordered hard-core bosons and the transverse field Ising model, where it successfully reproduces the known infinite randomness critical point with exponent psi ~ 0.43. Our main conclusion for disordered anyon models in two spatial dimensions is that systems of Ising anyons as well as systems of Fibonacci anyons do not realize infinite randomness phases, but flow back to weaker disorder under the numerical SDRG treatment.
We report on transport signatures of eight distinct bubble phases in the $N=3$ Landau level of a Al$_{x}$Ga$_{1-x}$As/Al$_{0.24}$Ga$_{0.76}$As quantum well with $x = 0.0015$. These phases occur near partial filling factors $ u^star approx 0.2,(0.8)$ and $ u^star approx 0.3,(0.7)$ and have $M = 2$ and $M = 3$ electrons (holes) per bubble, respectively. We speculate that a small amount of alloy disorder in our sample helps to distinguish these broken symmetry states in low-temperature transport measurements.
We perform a theoretical study, using {it ab initio} total energy density-functional calculations, of the effects of disorder on the $Mn-Mn$ exchange interactions for $Ga_{1-x}Mn_xAs$ diluted semiconductors. For a 128 atoms supercell, we consider a variety of configurations with 2, 3 and 4 Mn atoms, which correspond to concentrations of 3.1%, 4.7%, and 6.3%, respectively. In this way, the disorder is intrinsically considered in the calculations. Using a Heisenberg Hamiltonian to map the magnetic excitations, and {it ab initio} total energy calculations, we obtain the effective $JMn$, from first ($n=1$) all the way up to sixth ($n=6$) neighbors. Calculated results show a clear dependence in the magnitudes of the $JMn$ with the Mn concentration $x$. Also, configurational disorder and/or clustering effects lead to large dispersions in the Mn-Mn exchange interactions, in the case of fixed Mn concentration. Moreover, theoretical results for the ground-state total energies for several configurations indicate the importance of a proper consideration of disorder in treating temperature and annealing effects.
The zero temperature localization of interacting electrons coupled to a two-dimensional quenched random potential, and constrained to move on a fluctuating one-dimensional string embedded in the disordered plane, is studied using a perturbative renormalization group approach. In the reference frame of the electrons the impurities are dynamical and their localizing effect is expected to decrease. We consider several models for the string dynamics and find that while the extent of the delocalized regime indeed grows with the degree of string fluctuations, the critical interaction strength, which determines the localization-delocalization transition for infinitesimal disorder,does not change unless the fluctuations are softer than those of a simple elastic string.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
