Quantitative description of Josephson-like tunneling inνT=1quantum Hall bilayers

Abstract

At total filling factor ν T = 1, interlayer phase coherence in quantum Hall bilayers can result in a tunneling anomaly resembling the Josephson effect in the presence of strong fluctuations. The most robust experimental signature of this effect is a strong enhancement of the tunneling conductance at small voltages. The height and width of the conductance peak depend strongly on the area and tunneling amplitude of the samples, applied parallel magnetic field, and temperature. We find that the tunneling experiments are in quantitative agreement with a theory that treats fluctuations due to meron excitations phenomenologically and takes tunneling into account perturbatively. We also discuss the qualitative changes caused by larger tunneling amplitudes, and provide a possible explanation for recently observed critical currents in counterflow geometry.

Interplay between coherent and incoherent transport in quantum Hall bilayers

“…It is quantitatively well described by the theory of Hyart and Rosenow [15]. Intra layer transport shows a breakdown similar to the one observed at the integer quantum Hall effect.…”

“…With the observed critical Hall fields (E c = 8 ∼ 15 V/m for Corbino samples) an average distance between the merons can be estimated: ∆ ν=1 /(eE c ) = 600 ∼ 1000 nm. Our estimated length is only slightly larger than the length scale (a few hundred nm) derived theoretically by Hyart and Rosenow [15].…”

“…In general, the critical Josephson current follows the quadratic dependence on ∆ SAS . This gives a more stringent support to the perturbation theory [15] as only one parameter-the interlayer distance-is varied here. A deviation comes from samples with b = 8 nm reflecting that the breakdown threshold on the intralayer transport has been reached.…”

Exciton Condensation in Bilayer Quantum Hall Systems

“…Owing to the instability, the four-terminal voltage jumps discontinuously between essentially zero and a finite value as the critical current is approached. As a result, important region of the intrinsic four-terminal IV is excluded from measurement in strongly tunneling devices [50,78].…”

Diamagnetism and flux creep in bilayer exciton superfluids

“…A complete theory of dissipation and transport is beyond the scope of this work. Other mechanisms of dissipation will also play a role, such as the thermal excitation of vortices 45 as well as fermionic quasiparticles with an energy gap of the order of ρ s . It suffices to point out that the contribution from flux motion is not negligible in current samples.…”