pinecone/core-2020-05-10-deduplication huggingface dataset:
Evolution of superconducting gap anisotropy in hole-doped 122 iron
  pnictides

Motivated by recent experimental findings, we investigate the evolution of
the superconducting gap anisotropy in 122 iron pnictides as a function of hole
doping. Employing both a functional and a weak coupling renormalization group
approach (FRG and WRG), we analyse the Fermi surface instabilities of an
effective 122 model band structure at different hole dopings x, and derive the
gap anisotropy from the leading superconducting instability. In the transition
regime from collinear magnetism to s_{\pm}-wave, where strong correlations are
present, we employ FRG to identify a non- monotonous change of the gap
anisotropy in qualitative agreement with new experimental findings. From the
WRG, which is asymptotically exact in the weak coupling limit, we find an
s_{\pm}-wave to d-wave transition as a function of hole doping, complementing
previous findings from FRG [Thomale et al., Phys. Rev. Lett. 107, 117001
(2011)]. The gap anisotropy of the s_{\pm}-wave monotonously increases towards
the transition to d-wave as a function of x
Review on carrier multiplication in graphene

The remarkable gapless and linear band structure of graphene opens up new
carrier relaxation channels bridging the valence and the conduction band. These
Auger scattering processes change the number of charge carriers and can give
rise to a significant multiplication of optically excited carriers in graphene.
This is an ultrafast many-particle phenomenon that is of great interest both
for fundamental many-particle physics as well as technological applications.
Here, we review the research on carrier multiplication in graphene and
Landau-quantized graphene including theoretical modelling and experimental
demonstration
Nondestructive method of thin film dielectric constant measurements by
  two-wire capacitor

We suggest the nondestructive method for determination of the dielectric
constant of substrate-deposited thin films by capacitance measurement with two
parallel wires placed on top of the film. The exact analytical formula for the
capacitance of such system is derived. The functional dependence of the
capacitance on dielectric constants of the film, substrate, and environment
media and on the distance between the wires permits to measure the dielectric
constant of thin films for the vast set of parameters where previously proposed
approximate methods are less efficient.Comment: 7 pages, 5 figure
Violation of detailed balance for charge-transfer statistics in
  Coulomb-blockade systems

We discuss the possibility to generate in Coulomb-blockade systems steady
states that violate detailed balance. This includes both voltage biased and
non-biased scenarios. The violation of detailed balance yields that the
charge-transfer statistics for electrons tunneling into an island experiencing
strong Coulomb interaction is different from the statistics for tunneling out.
This can be experimentally tested by time-resolved measurement of the island's
charge state. We demonstrate this claim for two model systems.Comment: 7 pages, 6 figure
Electronic quantum optics beyond the integer quantum Hall effect

The analog of two seminal quantum optics experiments are considered in a
condensed matter setting with single electron sources injecting electronic wave
packets on edge states coupled through a quantum point contact. When only one
electron is injected, the measurement of noise correlations at the output of
the quantum point contact corresponds to the Hanbury-Brown and Twiss setup.
When two electrons are injected on opposite edges, the equivalent of the
Hong-Ou-Mandel collision is achieved, exhibiting a dip as in the coincidence
measurements of quantum optics. The Landauer-Buttiker scattering theory is used
to first review these phenomena in the integer quantum Hall effect, next, to
focus on two more exotic systems: edge states of two dimensional topological
insulators, where new physics emerges from time reversal symmetry and three
electron collisions can be achieved; and edges states of a hybrid
Hall/superconducting device, which allow to perform electron quantum optics
experiments with Bogoliubov quasiparticles.Comment: 13 pages, 10 figures, invited contribution for a focus issue on
  "Single-electron control in solid-state devices
Heat dissipation and fluctuations in a driven quantum dot

While thermodynamics is a useful tool to describe the driving of large
systems close to equilibrium, fluctuations dominate the distribution of heat
and work in small systems and far from equilibrium. We study the heat generated
by driving a small system and change the drive parameters to analyse the
transition from a drive leaving the system close to equilibrium to driving it
far from equilibrium. Our system is a quantum dot in a GaAs/AlGaAs
heterostructure hosting a two-dimensional electron gas. The dot is
tunnel-coupled to one part of the two-dimensional electron gas acting as a heat
and particle reservoir. We use standard rate equations to model the driven
dot-reservoir system and find excellent agreement with the experiment.
Additionally, we quantify the fluctuations by experimentally test the
theoretical concept of the arrow of time, predicting our ability to distinguish
whether a process goes in the forward or backward drive direction
Feedback-charging a metallic island

We consider electronic transport through a single-electron quantum dot that
is tunnel-coupled to an electronic lead and a metallic island. A background
reservoir keeps the metallic island at a thermal state with the ambient
temperature, while the charge accumulated on the island is reflected in a
time-dependent chemical potential. Without feedback, a current would flow
through the system until the chemical potentials of island and lead are
equilibrated. A feedback loop can be implemented by a quantum point contact
detecting the dot state, classical processing of the result and appropriate
feedback actions on the electronic tunneling rates taken, with the objective to
direct the current in a preferred direction. Since we directly take the
detector counting statistics into account, this automatically includes
measurement errors in the description. When mainly the rates are modified but
hardly any energy is exchanged with the system, this feedback loop effectively
implements a Maxwell demon, capable of transporting electrons against an
electric bias and thereby charging the metallic island. Once the feedback
protocol is stopped, the metallic island simply discharges. We find that a
quantitative detector model may be useful for a realistic statistical
description of feedback loops.Comment: invited contribution to special issue "Single-electron control in
  electronic devices" in Physica Status Solidi B 16 pages, 7 figure
Pauli spin blockade in CMOS double quantum dot devices

Silicon quantum dots are attractive candidates for the development of
scalable, spin-based qubits. Pauli spin blockade in double quantum dots
provides an efficient, temperature independent mechanism for qubit readout.
Here we report on transport experiments in double gate nanowire transistors
issued from a CMOS process on 300 mm silicon-on-insulator wafers. At low
temperature the devices behave as two few-electron quantum dots in series. We
observe signatures of Pauli spin blockade with a singlet-triplet splitting
ranging from 0.3 to 1.3 meV. Magneto-transport measurements show that
transitions which conserve spin are shown to be magnetic-field independent up
to B = 6 T.Comment: 5 pages , 4 figure
On-demand entanglement generation using dynamic single-electron sources

We review our recent proposals for the on-demand generation of entangled
few-electron states using dynamic single-electron sources. The generation of
entanglement can be traced back to the single-electron entanglement produced by
quantum point contacts acting as electronic beam splitters. The coherent
partitioning of a single electron leads to entanglement between the two
outgoing arms of the quantum point contact. We describe our various approaches
for generating and certifying entanglement in dynamic electronic conductors and
we quantify the influence of detrimental effects such as finite electronic
temperatures and other dephasing mechanisms. The prospects for future
experiments are discussed and possible avenues for further developments are
identified.Comment: Published version, 11 pages, 7 figures, short review for focus issue
  on 'Single-electron control in solid-state devices'. in Phys. Status Solidi B
  (2016
Phonon broadening from supercell lattice dynamics: random and correlated
  disorder

We demonstrate how supercell implementations of conventional lattice
dynamical calculations can be used to determine the extent and nature of
disorder-induced broadening in the phonon dispersion spectrum of disordered
crystalline materials. The approach taken relies on band unfolding, and is
first benchmarked against virtual crystal approximation phonon calculations.
The different effects of mass and interaction disorder on the phonon broadening
are then presented, focussing on the example of a simple cubic binary alloy.
For the mass disorder example, the effect of introducing correlated disorder is
also explored by varying the fraction of homoatomic and heteroatomic
neighbours. Systematic progression in the degree of phonon broadening, on the
one hand, and the form of the phonon dispersion curves from primitive to
face-centered cubic type, on the other hand, is observed as homoatomic
neighbours are disfavoured. The implications for rationalising selection rule
violations in disordered materials and for using inelastic neutron scattering
measurements as a means of characterising disorder are discussed.Comment: 6 pages, 3 figure
A deep-level transient spectroscopy study of p-type silicon Schottky barriers containing a Si-O superlattice

The presence of deep levels in a silicon-oxygen (Si-O) superlattice (SL) deposited on p-type silicon substrates has been investigated by deep-level transient spectroscopy (DLTS) on thermally evaporated Cr Schottky barriers (SBs). The SLs have been fabricated with different thicknesses of the silicon interlayers, formed by chemical vapor deposition. It is shown that a broad band of hole traps is present near the surface of the SB, which is associated with the SL. In addition, the activation energy corresponding with the peak maximum shifts to higher values with respect to the valence band and gives rise to a higher trap concentration with increasing silicon interlayer thickness. It is proposed that these states are associated with the structural defects found in similar SL structures, that is, with the epitaxial quality and not with the SiO bonds in the atomic layers. The change in the DLT-spectra with silicon thickness could be related with the transformation of the structural defects from small self-interstitial clusters to stacking faults
Entanglement-symmetry control in a quantum-dot Cooper-pair splitter

The control of nonlocal entanglement in solid state systems is a crucial
ingredient of quantum technologies. We investigate a Cooper-pair splitter based
on a double quantum dot realised in a semiconducting nanowire. In the presence
of interdot tunnelling the system provides a simple mechanism to develop
spatial entanglement even in absence of nonlocal coupling with the
superconducting lead. We discuss the possibility to control the symmetry
(singlet or triplet) of spatially separated, entangled electron pairs taking
advantage of the spin-orbit coupling of the nanowire. We also demonstrate that
the spin-orbit coupling does not impact over the entanglement purity of the
nonlocal state generated in the double quantum dot system.Comment: 7 pages, 3 figure
Relaxation of quantum dots in a magnetic field at finite bias -- charge,
  spin and heat currents

We perform a detailed study of the effect of finite bias and magnetic field
on the tunneling-induced decay of the state of a quantum dot by applying a
recently discovered general duality [PRB 93, 81411 (2016)]. This duality
provides deep physical insight into the decay dynamics of electronic open
quantum systems with strong Coulomb interaction. It associates the amplitudes
of decay eigenmodes of the actual system to the eigenmodes of a so-called dual
system with attractive interaction. Thereby, it predicts many surprising
features in the transient transport and its dependence on experimental control
parameters: the attractive interaction of the dual model shows up as sharp
features in the amplitudes of measurable time-dependent currents through the
actual repulsive system. In particular, for interacting quantum dots, the
time-dependent heat current exhibits a decay mode that dissipates the
interaction energy and that is tied to the fermion parity of the system. We
show that its decay amplitude has an unexpected gate-voltage dependence that is
robust up to sizable bias voltages and then bifurcates, reflecting that the
Coulomb blockade is lifted in the dual system. Furthermore, combining our
duality relation with the known Iche-duality, we derive new symmetry properties
of the decay rates as a function of magnetic field and gate voltage. Finally,
we quantify charge- and spin-mode mixing due to the magnetic field using a
single mixing parameter.Comment: 14 pages, 6 figure
Heat and charge transport measurements to access single-electron quantum
  characteristics

In the framework of the Floquet scattering-matrix theory we discuss how
electrical and heat currents accessible in mesoscopics are related to the state
of excitations injected by a single-electron source into an electron waveguide.
We put forward an interpretation of a single-particle heat current, which
differs essentially from that of an electrical current. We show that the
knowledge of both a time-dependent electrical current and a time-dependent heat
current allows the full reconstruction of a single-electron wave function. In
addition we compare electrical and heat shot noise caused by splitting of a
regular stream of single-electron excitations. If only one stream impinges on a
wave splitter, the heat shot noise is proportional to the well-known expression
of the charge shot noise, reflecting the partitioning of the incoming single
particles. The situation differs when two electronic streams collide at the
wave splitter. The shot noise suppression, due to the Pauli exclusion
principle, is governed by different overlap integrals in the case of charge and
of heat.Comment: 15 pages, 5 figures, invited contribution for a focus issue on
  'Single-electron control in solid-state devices' in Physica Status Solidi (b
Two-particle interferometry in quantum Hall edge channels

Since pioneering works of Hanbury-Brown and Twiss, intensity-intensity
correlations have been widely used in astronomical systems, for example to
detect binary stars. They reveal statistics effects and two-particle
interference, and offer a decoherence-free probe of the coherence properties of
light sources. In the quantum Hall edge channels, the concept of quantum optics
can transposed to electrons, and an analogous two-particle interferometry can
be developed, in order to characterize single-electron states. We review in
this article the recent experimental and theoretical progress on this topic.Comment: 14 pages, 10 figures, submitted for Physical Status Solidi B focus
  issue on 'Single-electron control in solid-state devices
Characterization and control of charge transfer in a tunnel junction

Charge transfer in a tunnel junction is studied under dc and ac voltage bias
using quantum shot noise. Under dc voltage bias $V$, spectral density of noise
measured within a very large bandwidth enables to deduce the current-current
correlator in the time domain by Fourier transform. This correlator exhibits
regular oscillations proving that electrons try to cross the junction
regularly, every $h/eV$. Using harmonic and bi-harmonic ac voltage bias, we
then show that quasiparticles excitations can be transferred through the
junction in a controlled way. By measuring the reduction of the excess shot
noise, we are able to determine the number of electron-hole pairs surrounding
the injected electrons and demonstrate that bi-harmonic voltage pulses realize
an on-demand electron source with a very small admixture of electron-hole
pairs.Comment: 8 pages, 8 figure
Electron quantum optics as quantum signal processing

The recent developments of electron quantum optics in quantum Hall edge
channels have given us new ways to probe the behavior of electrons in quantum
conductors. It has brought new quantities called electronic coherences under
the spotlight. In this paper, we explore the relations between electron quantum
optics and signal processing through a global review of the various methods for
accessing single- and two-electron coherences in electron quantum optics. We
interpret electron quantum optics interference experiments as analog signal
processing converting quantum signals into experimentally observable quantities
such as current averages and correlations.
  This point of view also gives us a procedure to obtain quantum information
quantities from electron quantum optics coherences. We illustrate these ideas
by discussing two mode entanglement in electron quantum optics. We also sketch
how signal processing ideas may open new perspectives for representing
electronic coherences in quantum conductors and understand the properties of
the underlying many-body electronic state.Comment: 19 pages, 9 figures, to appear in Physical Status Solidi B focus
  issue on 'Single-electron control in solid-state devices'. Version 2 & 3:
  expanded section 2 with extra-references reviewing electron quantum optics in
  other systems and updated bibliography+ corrected misprints + corrected Figs.
  8 & 9 and associated comments due to a small error in numerics: no change to
  conclusion
Localized defect states in MoS$_2$ monolayers: electronic and optical
  properties

Defects usually play an important role in tuning and modifying various
properties of semiconducting or insulating materials. Therefore we study the
impact of point and line defects on the electronic structure and optical
properties of MoS2 monolayers using density-functional methods. The different
types of defects form electronic states that are spatially localized on the
defect. The strongly localized nature is reflected in weak electronic
interactions between individual point or line defect and a weak dependence of
the defect formation energy on the defect concentration or line defect
separation. In the electronic energy spectrum the defect states occur as deep
levels in the band gap, as shallow levels very close to the band edges, as well
as levels in-between the bulk states. Due to their strongly localized nature,
all states of point defects are sharply peaked in energy. Periodic line defects
form nearly dispersionless one-dimensional band structures and the related
spectral features are also strongly peaked. The electronic structure of the
monolayer system is quite robust and it is well preserved for point defect
concentrations of up to 6%. The impact of point defects on the optical
absorption for concentrations of 1% and below is found to be very small. For
higher defect concentrations molybdenum vacancies were found to quench the
overall absorption and sulfur defects lead to sharp absorption peaks below the
absorption edge of the ideal monolayer. For line defects, we did not find a
considerable impact on the absorption spectrum. These results support recent
experiments on defective transition metal chalcogenides.Comment: 20 pages, 7 figures, 2 table
Levitons for electron quantum optics

Single electron sources enable electron quantum optics experiments where
single electrons emitted in a ballistic electronic interferometer plays the
role of a single photons emitted in an optical medium in Quantum Optics. A
qualitative step has been made with the recent generation of single charge
levitons obtained by applying Lorentzian voltage pulse on the contact of the
quantum conductor. Simple to realize and operate, the source emits electrons in
the form of striking minimal excitation states called levitons. We review the
striking properties of levitons and their possible applications in quantum
physics to electron interferometry and entanglement. W Schematic generation of
time resolved single charges called levitons using Lorentzian voltage pulses
applied on a contact. A Quantum Point Contact is used to partition the levitons
for further analysis. Injecting levitons on opposite contacts with a delay
$\\tau$ enables to probe electronic like Hong Ou Mandel correlations. Copyright
line will be provided by the publisher 1 Single electron sources In this
introduction, we will distinguish single charge sources from coherent single
electrons sources. The former have been developed for quantum metrology where
the goal is to transfer an integer charge at high frequency f through a
conductor with good accuracy to realize a quantized current source whose
current I = ef shows metrological accuracy. The latter, the coherent single
electrons source, aims at emitting (injecting) a single electron whose
wave-function is well defined and controlled to realize further single electron
coherent manipulation via quantum gates. The gates are provided by electronic
beam-splitters made with Quantum Point Contacts or provided by electronic
Mach-Zehnder and Fabry-Prot interferometers. Here it is important that the
injected single electron is the only excitation created in the conductor. The
frequency f of injection is not chosen to have a large current, as current
accuracy is not the goal, but only to get sufficient statistics on the electron
transfer events to extract physical information. 1.1 single charge sources for
current standards The first manipulation of single charges trace back to the
early 90's where physicists took advantage of charge quan-tization of a
submicronic metallic island nearly isolated from leads by tunnel barriers. The
finite energy E C = e 2 /2C to charge the small capacitor C with a single
charge being larger than temperature (typically one kelvin forComment: This an invited contribution submitted to a special issue on
  "single-electron control in solid-state devices
Reversing the Landauer's erasure: single-electron Maxwell's demon
  operating at the limit of thermodynamic efficiency

According to Landauer's principle, erasure of information is the only part of
a computation process that unavoidably involves energy dissipation. If done
reversibly, such an erasure generates the minimal heat of $k_BT\ln 2$ per
erased bit of information. The goal of this work is to discuss the actual
reversal of the optimal erasure which can serve as the basis for the Maxwell's
demon operating with ultimate thermodynamic efficiency as dictated by the
second law of thermodynamics. The demon extracts $k_BT\ln 2$ of heat from an
equilibrium reservoir at temperature $T$ per one bit of information obtained
about the measured system used by the demon. We have analyzed this Maxwell's
demon in the situation when it uses a general quantum system with a discrete
spectrum of energy levels as its working body. In the case of the effectively
two-level system, which has been realized experimentally based on tunneling of
individual electron in a single-electron box [J.V. Koski et al., PNAS 111,
13786 (2014)], we also studied and minimized corrections to the ideal
reversible operation of the demon. These corrections include, in particular,
the non-adiabatic terms which are described by a version of the classical
fluctuation-dissipation theorem. The overall reversibility of the Maxwell's
demon requires, beside the reversibility of the intrinsic working body
dynamics, the reversibility of the measurement and feedback processes. The
single-electron demon can, in principle, be made fully reversible by developing
a thermodynamically reversible single-electron charge detector for measurements
of the individual charge states of the single-electron box