Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userMesoscopic Fluctuations of Coulomb Drag of Composite Fermions
176
0
0.0
(
0
)
Authors
A. S. Price School ofn Physics
Ask ChatGPT about the research
No Arabic abstract
We present the first experimental study of mesoscopic fluctuations of Coulomb drag in a system with two layers of composite fermions, which are seen when either the magnetic field or carrier concentration are varied. These fluctuations cause an alternating sign of the average drag. We study these fluctuations at different temperatures to establish the dominant dephasing mechanism of composite fermions.
rate research
Read More
We consider mesoscopic fluctuations of Coulomb drag transresistivity between two layers at a Landau level filling factor $ u=1/2$ each. We find that at low temperature sample to sample fluctuations exceed both the ensemble average and the corresponding fluctuations at B=0. At the experimentally relevant temperatures, the variance of the transresistivity is proportional to $T^{-1/2}$. We find the dependence of this variance on density and magnetic field to reflect the attachment of two flux quanta to each electron.
We consider mesoscopic fluctuations of the Coulomb drag coefficient $rho_D$ in the system of two separated two-dimensional electron gases. It is shown that at low temperatures sample to sample fluctuations of $rho_D$ exceed its ensemble average. It means that in such a regime the sign of $rho_D$ is random and the temperature dependence almost saturates $rho_D sim 1/sqrt{T}$.
Using a novel structure, consisting of two, independently contacted graphene single layers separated by an ultra-thin dielectric, we experimentally measure the Coulomb drag of massless fermions in graphene. At temperatures higher than 50 K, the Coulomb drag follows a temperature and carrier density dependence consistent with the Fermi liquid regime. As the temperature is reduced, the Coulomb drag exhibits giant fluctuations with an increasing amplitude, thanks to the interplay between coherent transport in the graphene layer and interaction between the two layers.
Dirac fermions are actively investigated, and the discovery of the quantized anomalous Hall effect of massive Dirac fermions has spurred the promise of low-energy electronics. Some materials hosting Dirac fermions are natural platforms for interlayer coherence effects such as Coulomb drag and exciton condensation. Here we determine the role played by the anomalous Hall effect in Coulomb drag in massive Dirac fermion systems. We focus on topological insulator films with out-of plane magnetizations in both the active and passive layers. The transverse response of the active layer is dominated by a topological term arising from the Berry curvature. We show that the topological mechanism does not contribute to Coulomb drag, yet the longitudinal drag force in the passive layer gives rise to a transverse drag current. This anomalous Hall drag current is independent of the active-layer magnetization, a fact that can be verified experimentally. It depends non-monotonically on the passive-layer magnetization, exhibiting a peak that becomes more pronounced at low densities. These findings should stimulate new experiments and quantitative studies of anomalous Hall drag.
We show that the Coulomb interaction between two circuits separated by an insulating layer leads to unconventional thermoelectric effects, such as the cooling by thermal current effect, the transverse thermoelectric effect and Maxwells demon effect. The first refers to cooling in one circuit induced by the thermal current in the other circuit. The middle represents electric power generation in one circuit by the temperature gradient in the other circuit. The physical picture of Coulomb drag between the two circuits is first demonstrated for the case with one quantum dot in each circuits and then elaborated for the case with two quantum dots in each circuits. In the latter case, the heat exchange between the two circuits can vanish. Last, we also show that the Maxwells demon effect can be realized in the four-terminal quantum dot thermoelectric system, in which the quantum system absorbs the heat from the high-temperature heat bath and releases the same heat to the low-temperature heat bath without any energy exchange with the two heat baths. Our study reveals the role of Coulomb interaction in non-local four-terminal thermoelectric transport.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
