bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mapping electron delocalization by charge transport spectroscopy in an artificial molecule*
Authors: Gräber M.R. , Weiss M. , Keller D. , Oberholzer S. , Schönenberger C. 
Published: June 2022

AbstractIn this letter we present an experimental realization of the quantum mechanics textbook example of two interacting electronic quantum states that hybridize forming a molecular state. In our particular realization, the quantum states themselves are fabricated as quantum dots in a molecule, a carbon nanotube. For sufficient quantum‐mechanical interaction (tunnel coupling) between the two quantum states, the molecular wavefunction is a superposition of the two isolated (dot) wavefunctions. As a result, the electron becomes delocalized and a covalent bond forms. In this work, we show that electrical transport can be used as a sensitive probe to measure the relative weight of the two components in the superposition state as a function of the gate‐voltages. For the field of carbon nanotube double quantum dots, the findings represent an additional step towards the engineering of quantum states.
Counting statistics for the Anderson impurity model: Bethe ansatz and Fermi liquid study*
Authors: Gogolin A.O. , Konik R.M. , Ludwig A.W.W. , Saleur H. 
Published: June 2022

AbstractWe study the counting statistics of charge transport in the Anderson impurity model (AIM) employing both Keldysh perturbation theory in a Fermi liquid picture and the Bethe ansatz. In the Fermi liquid approach, the object of our principal interest is the generating function for the cumulants of the charge current distribution. We derive an exact analytic formula relating the full counting statistic (FCS) generating function to the self‐energy of the system in the presence of a measuring field. We first check that our approach reproduces correctly known results in simple limits, like the FCS of the resonant level system (AIM without Coulomb interaction). We then proceed to study the FCS for the AIM perturbatively in the Coulomb interaction. By comparing this perturbative analysis with a strong coupling expansion, we arrive at a conjecture for an expression for the FCS generating function at 𝒪(V3) (V is the voltage across the impurity) valid at all orders in the interaction. In the second part of the article, we examine a Bethe ansatz analysis of the current noise for the AIM. Unlike the Fermi liquid approach, here the goal is to obtain qualitative, not quantitative, results for a wider range of voltages both in and out of a magnetic field. Particularly notable are finite field results showing a double peaked structure in the current noise for voltages satisfying eV ∼ μB H. This double peaked structure is the “smoking gun” of Kondo physics in the current noise and is directly analogous to the single peak structure predicted in the differential conductance of the AIM.
Josephson junctions as detectors for non‐Gaussian noise*
Authors: Huard B. , Pothier H. , Birge N.O. , Esteve D. , Waintal X. , Ankerhold J. 
Published: June 2022

AbstractNon‐Gaussian fluctuations of the electrical current can be detected with a Josephson junction placed on‐chip with the noise source. We present preliminary measurements with an NIS junction as a noise source, and a Josephson junction in the thermal escape regime as a noise detector. It is shown that the Josephson junction detects not only the average noise, which manifests itself as an increased effective temperature, but also the noise asymmetry. A theoretical description of the thermal escape of a Josephson junction in presence of noise with a non‐zero third cumulant is presented, together with numerical simulations when the noise source is a tunnel junction with Poisson noise. Comparison between experiment and theory is discussed.
Interference of independently emitted electrons in quantum shot noise*
Authors: Büttiker M. , Samuelsson P. 
Published: June 2022

AbstractTheory predicts that electrons emitted from independent electron sources (metallic contacts) can nevertheless interfere. This interference is manifest in an exchange contribution to the shot noise correlation of currents at different contacts of a mesoscopic conductor. A geometry has been proposed in which second order (single particle) interference due to superposition of amplitudes is absent but fourth order (two‐particle) interference exhibits Aharonov‐Bohm oscillations. Recently such a geometry has been realized in an experiment and the theoretically predicted two‐particle Aharonov‐Bohm effect has been detected. We discuss Bell measurements and quantum state tomography using shot noise correlations. We discuss in addition structures in which two‐particle interference effects are generated dynamically by varying electrostatic potentials with the help of gates or by generating electron‐hole pairs by irradiating contacts of a mesoscopic conductor. These examples emphasize that two‐particle processes are not related to a particular geometry but are a general feature of multiparticle observables like shot noise correlations.
Circuit‐QED: How strong can the coupling between a Josephson junction atom and a transmission line resonator be?*
Authors: Devoret M.H. , Girvin Steven , Schoelkopf Robert 
Published: June 2022

AbstractAfter reviewing the limitation by the fine structure constant α of the dimensionless coupling constant of an hydrogenic atom with a mode of the electromagnetic field in a cavity, we show that the situation presents itself differently for an artificial Josephson atom coupled to a transmission line resonator. Whereas the coupling constant for the case where such an atom is placed inside the dielectric of the resonator is proportional to α1/2, the coupling of the Josephson atom when it is placed in series with the conducting elements of the resonator is proportional to α‐1/2 and can reach values greater than 1.
Nonlinear electrostatics: steps towards a neoclassical electron model
Authors: Delphenich D.H. 
Published: June 2022

AbstractThe equations of electrostatics are presented in pre‐metric form, and it is pointed out that if the origin of the nonlinearity is the constitutive law for the medium then the differential equations themselves remain linear, while the nonlinearity is confined to an algebraic equation. These equations are solved for a general class of electric fields that include the common textbook examples, namely, fields that are adapted to a coordinate vector field. The special forms that they then take for particular electric constitutive laws of quantum origin, namely, the constitutive laws derived from the Born–Infeld and Heisenberg–Euler Lagrangians, are then discussed. Finally, the classical problem of modeling the electron is redefined in light of the established facts of quantum physics.
Planck, units, and modern metrology*
Authors: Flowers Jeff L. , Petley Brian W. 
Published: June 2022

AbstractMax Planck was an early proponent of the use of units based on fundamental constants, his particular system included one involving the Planck constant which emerged from his work on black‐body radiation. In this review we discuss a number of such systems and how they have a strong interplay with modern metrology and the SI system of units.
Rigorous solution of a Hubbard model extended by nearest‐neighbour Coulomb and exchange interaction on a triangle and tetrahedron
Authors: Schumann R. 
Published: June 2022

AbstractThe Hubbard model extended by both nearest‐neighbour (nn) Coulomb correlation and nearest‐neighbour Heisenberg exchange is solved rigorously for a triangle and tetrahedron. All eigenvalues and eigenvectors are given as functions of the model parameters in a closed analytical form. For fixed electron numbers we found a multitude of level crossings, both in the ground state and in the excited states in dependence on the various model parameters. By coupling an ensemble of clusters to an electron bath we get the cluster gas model or the cluster gas approximation, if an extended array of weak‐interacting clusters is considered. The grand‐canonical potential Ω (μ, T, h) and the electron occupation N (μ, T, h) of the related cluster gases were calculated for arbitrary values (attractive and repulsive) of the three interaction constants. For the cluster gases without the additional interactions we found various steps in N (μ, T = 0, h = 0) higher than one. The reason is the degeneration of ground states differing in their electron occupation by more than one electron. For the triangular cluster gas we have one such degeneration point. For the tetrahedral cluster gas two. As a consequence, we do not find areas with one electron in the μ‐U ground‐state phase diagram of the triangular cluster gas or with one, two and five electrons in the case of the tetrahedral cluster gas. The degeneration point of the triangular cluster gas can not be destroyed by an applied magnetic field. This holds also for the lower degeneration point of the tetrahedral cluster gas. Otherwise, the upper degeneration point breaks down at a critical magnetic field hc. The dependence of hc on U shows a maximum for strong on‐site correlation. The influence of nn‐exchange and nn‐Coulomb correlation on the ground‐state phase diagrams is calculated. Whereas antiferromagnetic nn‐exchange breaks the degeneration points of the tetrahedral cluster gas partially only, a repulsive nn‐Coulomb correlation lifts the underlying degeneracies completely. Otherwise both ferromagnetic nn‐exchange and attractive nn‐Coulomb interaction stabilise the degeneration points. The consequences of the cluster gas results for extended cluster arrays are discussed.
A novel approach to Ising problems
Authors: Hoede C. , Zandvliet H.J.W. 
Published: June 2022

AbstractIn 2000 Istrail suggested that calculating the partition function of non‐planar Ising models is an NP‐complete problem, implying that these problems are intractable and thus essentially unsolvable. In this note we discuss the validity of this suggestion and introduce the idea of gauging on an exact equation. We illustrate how this method works by applying it to two non‐planar Ising models, namely the 2D model with nearest and weak next nearest neighbor interactions and the anisotropic 3D model.
“… you can't say to anyone to their face: your paper is rubbish.” Max Planck as Editor of theAnnalen der Physik*
Authors: Hoffmann D. 
Published: June 2022

AbstractMax Planck's place in the history of theAnnalen der Physik, which spans some two hundred years, can be characterized as unique. Planck not only published the majority of his own scientific papers in this periodical but was also connected to it personally in various editorial positions. Thus for over half a century, from 1894 until 1947, he contributed decisively toward its promotion as a leading international professional journal of modern physics. This paper documents Planck's diverse relationships with theAnnalen der Physikand analyzes his editorship against the backdrop of the evolving physics in the first quarter of the 20th century.
Ettore Majorana and his heritage seventy years later
Authors: Esposito S. 
Published: June 2022

AbstractThe physicists working in several areas of research know quite well the name of Ettore Majorana, since it is currently associated to fundamental concepts likeMajorana neutrinosin particle physics and cosmology orMajorana fermionsin condensed matter physics. But, probably, very few is known about other substantial contributions of that ingenious scholar, and even less about his personal background. For non specialists, instead, the name of Ettore Majorana is usually intimately related to the fact that he disappeared rather mysteriously on March 26, 1938, just seventy years ago, and was never seen again. The life and the work of this Italian scientist is the object of the present review, which will also offer a summary of the main results achieved in recent times by the historical and scientific researches on his work.
On the construction of Fermi‐Walker transported frames
Authors: Maluf J.W. , Faria F.F. 
Published: June 2022

AbstractWe consider tetrad fields as reference frames adapted to observers that move along arbitrary timelike trajectories in spacetime. By means of a local Lorentz transformation we can transform these frames into Fermi‐Walker transported frames, which define a standard of non‐rotation for accelerated observers. Here we present a simple prescription for the construction of Fermi‐Walker transported frames out of an arbitrary set of tetrad fields.
Pressure driven transport of glassy solid helium in cylindrical nanopores at very low temperature regime
Authors: Kwang‐Hua Chu Z. 
Published: June 2022

AbstractBy using the glassy helium model and boundary perturbation method, we can obtain the velocity fields (as well as the flow rate up to the second order) at very low temperature regime inside the wavy‐rough cylindrical nanopores. Our results show that the velocities of solid helium reported before by many groups could be reproduced by carefully selecting relevant physical parameters.
Coherence theory and coherence phenomena in a closed spin‐1/2 system
Authors: Dannenberg O. 
Published: June 2022

AbstractA simplified Heisenberg spin model is studied in order to examine the idea of decoherence in closed quantum systems. For this purpose, we present a quantifiable definition to quantum coherence Ξ, and discuss in some detail a general coherence theory and its elementary results. As expected, decoherence is understood as a statistical process that is caused by the dynamics of the system, similar to the growth of entropy. It appears that coherence is an important measure that helps to understand quantum properties of a system, e.g., the decoherence time can be derived from the coherence function Ξ(t), but not from the entropy dynamics. Moreover, the concept of decoherence time is applicable in closed and finite systems. However, in most cases, the decay of off‐diagonal elements differs from the usual exp(‐t/τd) behaviour. For concreteness, we report the form of decoherence time τdin a finite Heisenberg model with respect to the number of particles N, density nρ, spatial dimension D and ϵ in a η/rϵ‐type of potential.
Entanglement in a periodic quench
Authors: Eisler V. , Peschel I. 
Published: June 2022

AbstractWe consider a chain of free electrons with periodically switched dimerization and study the entanglement entropy of a segment with the remainder of the system. We show that it evolves in a stepwise manner towards a value proportional to the length of the segment and displays in general slow oscillations. For particular quench periods and full dimerization an explicit solution is given. Relations to equilibrium lattice models are pointed out.
Strings in strongly correlated electron systems
Authors: Fulde P. , Pollmann F. 
Published: June 2022

AbstractIt is shown that strongly correlated electrons on frustrated lattices like pyrochlore, checkerboard or kagomè lattice can lead to the appearance of closed and open strings. They are resulting from nonlocal subsidiary conditions which propagating strongly correlated electrons require. The dynamics of the strings is discussed and a number of their properties are pointed out. Some of them are reminiscent of particle physics.
Electronic structure calculations for inhomogeneous systems: Interfaces, surfaces, and nanocontacts
Authors: Schwingenschlögl U. , Schuster C. 
Published: June 2022

AbstractThe article gives an introduction into the application of density functional theory (DFT) to inhomogeneous systems. To begin with, we describe the interplay of specific materials at interfaces, resulting in structure relaxation and modifications of the chemical bonding. We address interfaces between YBa2Cu3O7 and a normal metal, in order to quantify the intrinsic interface charge transfer into the superconductor. Moreover, we study the internal interfaces in a V6O13 battery cathode and the effects of ion incorporation during the charging and discharging process. The second part of the article deals with the influence of surfaces on the nearby electronic states. Here, we investigate a LaAlO3/SrTiO3 heterostructure in a thin film geometry. We particularly explain the experimental dependence of the electronic states at the heterointerface on the surface layer thickness. Afterwards, surface relaxations are studied for both the clean Ge(001) surface and for self‐assembled Pt nanowires on Ge(001). In the third part, we turn to atomic and molecular contacts. We compare the properties of prototypical Al nanocontact geometries, aiming at insight into the chemical bonding and the occupation of the atomic orbitals. Finally, the local electronic structure of a benzene‐1,4‐dithiol molecule between two Au electrodes is discussed as an example for a molecular bridge.
Proof of a decomposition theorem for symmetric tensors on spaces with constant curvature
Authors: Straumann N. 
Published: June 2022

AbstractIn cosmological perturbation theory a first major step consists in the decomposition of the various perturbation amplitudes into scalar, vector and tensor perturbations, which mutually decouple. In performing this decomposition one uses – beside the Hodge decomposition for one‐forms – an analogous decomposition of symmetric tensor fields of second rank on Riemannian manifolds with constant curvature. While the uniqueness of such a decomposition follows from Gauss' theorem, a rigorous existence proof is not obvious. In this note we establish this for smooth tensor fields, by making use of some important results for linear elliptic differential equations.
Special relativity in the 21st century*
Authors: Cacciatori S. , Gorini V. , Kamenshchik A. 
Published: June 2022

AbstractThis paper, which is meant to be a tribute to Minkowski's geometrical insight, rests on the idea that the basic observed symmetries of spacetime homogeneity and of isotropy of space, which are displayed by the spacetime manifold in the limiting situation in which the effects of gravity can be neglected, leads to a formulation of special relativity based on the appearance of two universal constants: a limiting speedcand a cosmological constant Λ which measures a residual curvature of the universe, which is not ascribable to the distribution of matter‐energy. That these constants should exist is an outcome of the underlying symmetries and is confirmed by experiments and observations, which furnish their actual values. Specifically, it turns out on these foundations that the kinematical group of special relativity is the de Sitter groupdS(c, Λ) =SO(1,4). On this basis, we develop at an elementary classical and, hopefully, sufficiently didactical level the main aspects of the theory of special relativity based onSO(1,4) (de Sitter relativity). As an application, we apply the formalism to an intrinsic formulation of point particle kinematics describing both inertial motion and particle collisions and decays.
Perfect electromagnetic conductor medium
Authors: Sihvola A. , Lindell I.V. 
Published: June 2022

AbstractThis article presents a review of a novel concept in electromagnetics, the Perfect Electromagnetic Conductor (PEMC). In the Minkowskian representation of the material response to electromagnetic fields, PEMC corresponds to the axion part of the constitutive tensor. From the electrical engineering point of view, PEMC is a generalization of the perfect electric conductor (PEC) and perfect magnetic conductor (PMC) materials which are useful concepts as ideal boundaries in the modeling of electromagnetic problems. PEMC is characterized by a pseudoscalar, admittance‐type parameterM, with limits 1/M→ (PEC) andM→ (PMC). This paper discusses how the PECM medium as a boundary or in particulate form generalizes earlier known electromagnetic problems (reflection, scattering, materials modeling, waveguides, resonators, image principles). The main effect of PEMC boundary is to rotate the polarization plane of the reflected electric field vector. Also practical realization aspects of a PEMC medium are discussed in the paper.
The Weinberg‐Witten theorem on massless particles: an essay
Authors: Loebbert F. 
Published: June 2022

AbstractIn this essay we deal with the Weinberg‐Witten theorem [1] which imposes limitations on massless particles. First we motivate a classification of massless particles given by the Poincaré group as the symmetry group of Minkowski spacetime. We then use the fundamental structure of the background in the form of Poincaré covariance to derive restrictions on charged massless particles known as the Weinberg‐Witten theorem. We address possible misunderstandings in the proof of this theorem motivated by several papers on this topic. In the last section the consequences of the theorem are discussed. We treat it in the context of known particles and as a constraint for emergent theories.
Vacuum driven accelerated expansion*
Authors: Broda B. , Bronowski P. , Ostrowski M. , Szanecki M. 
Published: June 2022

AbstractIt has been shown that an improved estimation of the quantum vacuum energy can yield not only theoretically acceptable but also experimentally realistic results. Our idea consists in a straightforward extraction of the gravitationally interacting part of the full quantum vacuum energy by means of gauge transformations. The implementation of this idea has been performed, in the background of a Friedmann‐Lemaître‐Robertson‐Walker geometry, by means of the euclidean version of the effective action formalism, in the language of Schwinger's proper time and Seeley‐DeWitt's heat kernel expansion.
Comment to “No‐go result for supersymmetric gauge theories in the causal approach”, by D. R. Grigore and G. Scharf (previous article: Ann. Phys. (Berlin) 17, 864 (2008))
Authors: Sibold K. 
Published: June 2022

AbstractFulfilling a request of the editor I try to put the aforementioned paper into perspective of relevant results obtained before. In particular I point out that supersymmetry of the S‐operator in cases where it exists is not necessarily in danger. Local couplings reveal however that some composite operators undergo a breaking of their supercovariance, a fact which has been established by Elisabeth Kraus.
Symanzik's method applied to fractional quantum Hall edge states
Authors: Blasi A. , Ferraro D. , Maggiore N. , Magnoli N. , Sassetti M. 
Published: June 2022

AbstractThe method of separability, introduced by Symanzik, is applied in order to describe the effect of a boundary for a fractional quantum Hall liquid in the Laughlin series. An Abelian Chern‐Simons theory with plane boundary is considered and the Green functions both in the bulk and on the edge are constructed, following a rigorous, perturbative, quantum field theory treatment. We show that the conserved boundary currents find an explicit interpretation in terms of the continuity equation with the electron density satisfying the Tomonaga‐Luttinger commutation relation.
Approximate record length constraints for experimental identification of dynamical fractals
Authors: Fleming S.W. 
Published: June 2022

AbstractThe ambiguity that can exist, for short datasets, between the observational power spectra of dynamical fractals and low‐order linear memory processes is demonstrated and explained. It is argued that it could be broadly useful to have a highly practical rule‐of‐thumb for assessing whether a data record is sufficiently long to permit distinguishing the two types of processes, and if it is not, to produce an approximate estimate of the amount of additional data that would be required to do so. Such an expression is developed using the AR(1) process as a loose benchmark. Various aspects of the technique are successfully tested using synthetic time series generated by a range of prescribed models, and its application and relevance to observational datasets is then demonstrated using examples from mathematical ecology (wild steelhead population size), geophysics (river flow volume), and econophysics (stock price volatility).