Abstract
In view of the extensive use of hexagonal boron nitride (hBN) in 2D material electronics, it becomes important to refine its dielectric characterization in terms of low-field permittivity ...and high-field strength and conductivity up to the breakdown voltage. The present study aims at filling this gap using DC and RF transport in two Au-hBN-Au capacitor series of variable thickness in the 10–100 nm range, made of large high-pressure, high-temperature (HPHT) crystals and a polymer derivative ceramics (PDC) crystals. We deduce an out-of-plane low field dielectric constant
ϵ
∥
= 3.4 ± 0.2 consistent with the theoretical prediction of Ohba
et al
, that narrows down the generally accepted window
ϵ
∥
= 3–4. The DC-current leakage at high-field is found to obey the Frenkel-Pool law for thermally-activated trap-assisted electron transport with a dynamic dielectric constant
ϵ
∥
≃ 3.1 and a trap energy Φ
B
≃ 1.3 eV, that is comparable with standard technologically relevant dielectrics.
The paradigm of graphene transistors is based on the gate modulation of the channel carrier density by means of a local channel gate. This standard architecture is subject to the scaling limit of the ...channel length and further restrictions due to access and contact resistances impeding the device performance. We propose a novel design, overcoming these issues by implementing additional local gates underneath the contact region which allow a full control of the Klein barrier taking place at the contact edge. In particular, our work demonstrates the GHz operation of transistors driven by independent contact gates. We benchmark the standard channel and novel contact gating and report for the later dynamical transconductance levels at the state of the art. Our finding may find applications in electronics and optoelectronics whenever there is need to control independently the Fermi level and the electrostatic potential of electronic sources or to get rid of cumbersome local channel gates.
We report on microwave operation of top-gated single carbon nanotube transistors. From transmission measurements in the 0.1−1.6 GHz range, we deduce device transconductance g m and gate−nanotube ...capacitance C g of micro- and nanometric devices. A large and frequency-independent g m ∼ 20 μS is observed on short devices, which meets the best dc results. The capacitance per unit gate length of 60 aF/μm is typical of top gates on a conventional oxide with ε ∼ 10. This value is a factor of 3−5 below the nanotube quantum capacitance which, according to recent simulations, favors high transit frequencies f T = g m/2πC g. For our smallest devices, we find a large f T ∼ 50 GHz with no evidence of saturation in length dependence.
Breakdown of the quantum Hall effect (QHE) is commonly associated with an electric field approaching the inter-Landau-level (LL) Zener field, the ratio of the Landau gap and the cyclotron radius. ...Eluded in semiconducting heterostructures, in spite of extensive investigation, the intrinsic Zener limit is reported here using high-mobility bilayer graphene and high-frequency current noise. We show that collective excitations arising from electron-electron interactions are essential. Beyond a noiseless ballistic QHE regime a large super-Poissonian shot noise signals the breakdown via inter-LL scattering. The breakdown is ultimately limited by collective excitations in a regime where phonon and impurity scattering are quenched. The breakdown mechanism can be described by a Landau critical velocity as it bears strong similarities with the roton mechanism of superfluids. In addition, we show that breakdown is a precursor of an electric-field induced QHE-metal transition.
The original version of this Article contained an error in the author affiliations. Affiliation 3 incorrectly read "Centre de Nanosciences et de Nanotechnologies (C2N), CNRS, Univ. Paris Sud, ...Université Paris-Saclay, 91190, Saint-Aubin, France". This has now been corrected in both the PDF and HTML versions of the Article.
Electron quantum optics aims at the controlled manipulation and measurement of the quantum state of a single to few electrons in metallic nanostructures comparable to recent achievements with ...microwave photons, light or cold atoms. Mach-Zenhder interference experiments in integer quantum Hall edge channels as well as the demonstration of an on-demand single electron source have risen the hope for electron quantum optics experiments in ballistic conductors. However the wavefunction of a coherent single electron excitation has never been imaged. Here, we propose a quantum tomography protocol to measure single electron coherence in quantum Hall edge channels analogous to homodyne tomography in quantum optics. Single electron quantum tomography would be a major step in electron quantum optics with applications ranging from characterization of single to few electron sources to quantitative studies of single electron decoherence in nanostructures. We discuss how this proposal could be implemented using recently developed ultrahigh sensitivity noise measurement schemes.
We present the first study of the statistics of GHz photons in quantum circuits, using Hanbury Brown and Twiss correlations. The super-Poissonian and Poissonian photon statistics of thermal and ...coherent sources, respectively, made of a resistor and a radio frequency generator, are measured down to the quantum regime at milli-Kelvin temperatures. As photon correlations are linked to the second and fourth moments of current fluctuations, this experiment, which is based on current cryogenic electronics, may become a standard for probing electron/photon statistics in quantum conductors.
We study time dependent electronic transport along the chiral edge channels of the quantum Hall regime, focusing on the role of Coulomb interaction. In the low frequency regime, the a.c. conductance ...can be derived from a lumped element description of the circuit. At higher frequencies, the propagation equations of the Coulomb coupled edge channels need to be solved. As a consequence of the interchannel coupling, a charge pulse emitted in a given channel fractionalized in several pulses. In particular, Coulomb interaction between channels leads to the fractionalization of a charge pulse emitted in a given channel in several pulses. We finally study how the Coulomb interaction, and in particular the fractionalization process, affects the propagation of a single electron in the circuit. All the above-mentioned topics are illustrated by experimental realizations.
•We discuss Coulomb interaction effects on charge propagation along quantum Hall edge channels.•Various experimental works are connected and analyzed in a unified theoretical framework.•Low frequency transport is described by a lumped element model.•High frequency transport is described by edge magnetoplasmon propagation.•Interchannel magnetoplasmon scattering leads to electron fractionalization and decoherence.
The controlled and accurate emission of coherent electronic wave packets is of prime importance for future applications of nanoscale electronics. Here, we present a theoretical and experimental ...analysis of the finite-frequency noise spectrum of a periodically driven single-electron emitter. The electron source consists of a mesoscopic capacitor that emits single electrons and holes into a chiral edge state of a quantum Hall sample. We compare experimental results with two complementary theoretical descriptions: on the one hand, the Floquet scattering theory that leads to accurate numerical results for the noise spectrum under all relevant operating conditions, and on the other hand, a semiclassical model that enables us to develop an analytic description of the main sources of noise when the emitter is operated under optimal conditions. We find excellent agreement between experiment and theory. Importantly, the noise spectrum provides us with an accurate description and characterization of the mesoscopic capacitor when operated as a periodic single-electron emitter.
We report on the GHz complex admittance of a chiral one-dimensional ballistic conductor formed by edge states in the quantum Hall regime. The circuit consists of a wide Hall bar (the inductor L) in ...series with a tunable resistor (R) formed by a quantum point contact. Electron interactions between edges are screened by a pair of side gates. Conductance steps are observed on both real and imaginary parts of the admittance. Remarkably, the phase of the admittance is transmission independent. This shows that the relaxation time of a chiral R -L circuit is resistance independent. A current and charge conserving scattering theory is presented that accounts for this observation with a relaxation time given by the electronic transit time in the circuit.
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