Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userFrictional magneto-Coulomb drag in graphene double-layer heterostructure
80
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Coulomb interaction between two closely spaced parallel layers of electron system can generate the frictional drag effect by interlayer Coulomb scattering. Employing graphene double layers separated by few layer hexagonal boron nitride (hBN), we investigate density tunable magneto- and Hall-drag under strong magnetic fields. The observed large magneto-drag and Hall-drag signals can be related with Laudau level (LL) filling status of the drive and drag layers. We find that the sign and magnitude of the magneto- and Hall-drag resistivity tensor can be quantitatively correlated to the variation of magneto-resistivity tensors in the drive and drag layers, confirming a theoretical formula for magneto-drag in the quantum Hall regime. The observed weak temperature dependence and $sim B^2$ dependence of the magneto-drag are qualitatively explained by Coulomb scattering phase-space argument.
rate research
Read More
The first order contribution to frictional drag in bi-layered fermion gas is examined. We discuss the relevance of single photon exchange in the evaluation of transresistance, which is usually explained by second order effects such as Coulomb and phonon drag. Since the effective e.m. interaction is unscreened, in the d.c. limit we obtain a finite (and large) contribution to transconductivity.
Coulomb drag between parallel quantum wells provides a uniquely sensitive measurement of electron correlations since the drag response depends on interactions only. Recently it has been demonstrated that a new regime of strong interactions can be accessed for devices consisting of two monlolayer graphene (MLG) crystals, separated by few layer hexagonal boron-nitride. Here we report measurement of Coulomb drag in a double bilayer graphene (BLG) stucture, where the interaction potential is anticipated to be yet further enhanced compared to MLG. At low temperatures and intermediate densities a new drag response with inverse sign is observed, distinct from the momentum and energy drag mechanisms previously reported in double MLG. We demonstrate that by varying the device aspect ratio the negative drag component can be suppressed and a response showing excellent agreement with the density and temperature dependance predicted for momentum drag in double BLG is found. Our results pave the way for pursuit of emergent phases in strongly interacting bilayers, such as the exciton condensate.
Two-dimensional systems that host one-dimensional helical states are exciting from the perspective of scalable topological quantum computation when coupled with a superconductor. Graphene is particularly promising for its high electronic quality, versatility in van der Waals heterostructures and its electron and hole-like degenerate 0$th$ Landau level. Here, we study a compact double layer graphene SQUID (superconducting quantum interference device), where the superconducting loop is reduced to the superconducting contacts, connecting two parallel graphene Josephson junctions. Despite the small size of the SQUID, it is fully tunable by independent gate control of the Fermi energies in both layers. Furthermore, both Josephson junctions show a skewed current phase relationship, indicating the presence of superconducting modes with high transparency. In the quantum Hall regime we measure a well defined conductance plateau of 2$e^2/h$ an indicative of counter propagating edge channels in the two layers. Our work opens a way for engineering topological superconductivity by coupling helical edge states, from graphenes electron-hole degenerate 0$th$ Landau level via superconducting contacts.
We have fabricated bilayer-graphene double layers separated by a thin ($sim$20 nm) boron nitride layer and performed Coulomb drag and counterflow thermoelectric transport measurements. The measured Coulomb drag resistivity is nearly three orders smaller in magnitude than the intralayer resistivities. The counterflow Seebeck coefficient is found to be well approximated by the difference between Seebeck coefficients of individual layers and exhibit a peak in the regime where two layers have opposite sign of charge carriers. The measured maximum counterflow power factor is $sim$ 700 $mu$W/K$^2$cm at room temperature, promising high power output per mass for lightweight thermoelectric applications. Our devices open a possibility for exploring the novel regime of thermoelectrics with tunable interactions between n-type and p-type channels based on graphene and other two-dimensional materials and their heterostructures.
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.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
