A Platform for Measuring Ion Diffusion in Strongly Coupled Plasmas.
Abstract not provided.
Knapp, Patrick↗
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Evolving images of the proton: Hadron physics over the past 40 years
Once upon a time, the world was simple: the proton contained three quarks, two ups and a down. How these give the proton its mass and its spin seemed obvious. Over the past 40 years the proton has become more complicated, and how even these most obvious of its properties is explained in a universe of quarks, antiquarks and gluons remains a challenge. That this should be so should come as no surprise. Quantum chromodynamics, the theory of the strong interaction, is seemingly simple, and its consequences are straightforward in the domain of hard scattering where perturbation theory applies. However, the beauty of the hadron world is its diversity. The existence of hadrons, their properties, and their binding into nuclei do not appear in the Lagrangian of QCD. They all emerge as a result of its strong coupling. Strong coupling QCD creates complex phenomena, much richer than known 40 years ago: a richness that ensures colour confinement and accounts for more than 95% of the mass of the visible Universe. How strong coupling QCD really works requires a synergy between experiment and theory. Furthermore, a very personal view of these fascinating developments in cold QCD is presented.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Properties of the Lambda(1405) Hyperon Studied at CLAS Using Photoproduction
The internal structure of the Lambda(1405) hyperon has remained an unresolved mystery in hadron physics for decades. Observed as a resonance in sigma pi just below the N-Kbar threshold, it is the first excited Lambda state; yet the nature of this resonance, where it belongs in the hierarchy of hyperons, and some of its basic properties, remain unsettled. In previous experiments, the invariant mass spectrum (lineshape) has been observed to be distorted from a simple Breit-Wigner form, and since the 1960's, this has lead to theoretical speculation on the nature of this resonance and the dynamics involved in forming it. Dalitz was among the first to point out that the strong attraction of the N-Kbar channel near threshold could produce a quasi-bound state that can only decay to the below-threshold Sigma pi mode. The otherwise highly successful constituent quark model has difficulties in assigning the Lambda(1405), since naively the mass is calculated to be almost degenerate with the Lambda(1520). In recent years, advances in chiral unitary models have made definite predictions for the line shape of the Lambda(1405), based on a strong coupling approach, to dynamically generate the Lambda(1405) from constituent mesons and baryons. Furthermore, the chiral unitary model predicts that there are two I = 0 poles for the Lambda(1405), one coupling strongly to the Sigma pi decay mode, and the other a narrower resonance that couples more strongly to N-Kbar. The composite nature of the Lambda(1405) has repercussions, such as to the nature of baryon resonances above 1.9 GeV in mass which may decay to Lambda(1405), and also the topic of kaon condensation in the nuclear medium. Past experiments have shown distortions of the line shape of the Lambda(1405), but had statistics too limited to draw strong conclusions. With the CLAS collaboration at Jefferson Lab, we have studied the Lambda(1405) via photoproduction with unprecedented statistics from a proton target. The large multi-particle acceptance of the CLAS detector allows us to measure and compare the lineshapes and differential cross sections of all three decay modes Sigma^+ pi^?,Sigma0pi0, and sigma? pi+ from near the production threshold up to center-of-mass energies of 2.84 GeV. As predicted in the chiral unitary models, the line shapes and differential cross sections of the Lambda(1405) are indeed quite different for each decay channel. This lends support to the idea that the Lambda(1405) has strong dynamical components that distinguish it from other known resonances. In addition, the cross sections of the nearby Sigma(1385) and Lambda(1520) resonances have also been measured, and comparisons to the Lambda(1405) cross section will be shown. Another basic property of the Lambda(1405) that has previously been experimentally unconfirmed is its spin and parity quantum numbers. Past experiments have not shown a conclusive result for the expected spin and parity of JP= 1/2?. In the CLAS experiment we found a substantial polarization of the photoproduced Lambda(1405), which is measured through the daughter Sigma+, and we determined the parity of the parent Lambda(1405) from how this polarization was transferred. Our spin-parity analysis shows that indeed the assignment of 1/2? is correct.
Moriya, Kei↗
Effects of Coulomb coupling on friction in strongly magnetized plasmas
The friction force on a test particle traveling through a plasma that is both strongly coupled and strongly magnetized is studied using molecular dynamics simulations. In addition to the usual stopping power component aligned antiparallel to the velocity, a transverse component that is perpendicular to both the velocity and Lorentz force is observed. This component, which was recently discovered in weakly coupled plasmas, is found to increase in both absolute and relative magnitude in the strongly coupled regime. Strong coupling is also observed to induce a third component of the friction force in the direction of the Lorentz force. These first-principles simulations reveal novel physics associated with collisions in strongly coupled, strongly magnetized, plasmas that are not predicted by existing kinetic theories. The effect is expected to influence macroscopic transport in a number of laboratory experiments and astrophysical plasmas.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Microwave-driven coherent operation of a semiconductor quantum dot charge qubit
An intuitive realization of a qubit is an electron charge at two well-defined positions of a double quantum dot. The qubit is simple and has the potential for high-speed operation because of its strong coupling to electric fields. But, charge noise also couples strongly to this qubit, resulting in rapid dephasing at all but one special operating point called the ‘sweet spot’. In previous studies d.c. voltage pulses have been used to manipulate semiconductor charge qubits but did not achieve high-fidelity control, because d.c. gating requires excursions away from the sweet spot. Here, by using resonant a.c. microwave driving we achieve fast (greater than gigahertz) and universal single qubit rotations of a semiconductor charge qubit. The Z-axis rotations of the qubit are well protected at the sweet spot, and we demonstrate the same protection for rotations about arbitrary axes in the X–Y plane of the qubit Bloch sphere. We characterize the qubit operation using two tomographic approaches: standard process tomography and gate set tomography. Moreover, both methods consistently yield process fidelities greater than 86% with respect to a universal set of unitary single-qubit operations.
77 NANOSCIENCE AND NANOTECHNOLOGY↗
Tunable exciton-polaritons emerging from WS 2 monolayer excitons in a photonic lattice at room temperature
Engineering non-linear hybrid light-matter states in tailored lattices is a central research strategy for the simulation of complex Hamiltonians. Excitons in atomically thin crystals are an ideal active medium for such purposes, since they couple strongly with light and bear the potential to harness giant non-linearities and interactions while presenting a simple sample-processing and room temperature operability. We demonstrate lattice polaritons, based on an open, high-quality optical cavity, with an imprinted photonic lattice strongly coupled to excitons in a WS 2 monolayer. We experimentally observe the emergence of the canonical band-structure of particles in a one-dimensional lattice at room temperature, and demonstrate frequency reconfigurability over a spectral window exceeding 85 meV, as well as the systematic variation of the nearest-neighbour coupling, reflected by a tunability in the bandwidth of the p-band polaritons by 7 meV. The technology presented in this work is a critical demonstration towards reconfigurable photonic emulators operated with non-linear photonic fluids, offering a simple experimental implementation and working at ambient conditions.
36 MATERIALS SCIENCE↗
An Alternative View of the Dynamical Origin of the P11 Nucleon Resonances: Results from the Excited Baryon Analysis Center
We present an alternative interpretation for the dynamical origin of the P{sub 11} nucleon resonances, which results from the dynamical coupled-channels analysis at Excited Baryon Analysis Center of Jefferson Lab. The results indicate the crucial role of the multichannel reaction dynamics in determining the N* spectrum. An understanding of the spectrum and structure of the excited nucleon (N*) states is a fundamental challenge in the hadron physics. The N* states, however, couple strongly to the meson-baryon continuum states and appear only as resonance states in the {gamma}N and {pi}N reactions. One can expect from such strong couplings that the (multichannel) reaction dynamics will affect significantly the N* states and cannot be neglected in extracting the N* parameters from the data and giving physical interpretations. It is thus well recognized nowadays that a comprehensive study of all relevant meson production reactions with {pi}N,{eta}N,{pi}{pi}N,KY, {hor_ellipsis} final states is necessary for a reliable extraction of the N* parameters. To address this challenging issue, the Excited Baryon Analysis Center (EBAC) of Jefferson Lab has been conducting the comprehensive analysis of the world data of {gamma}N,{pi}N {yields} {pi}N,{eta}N,{pi}{pi}N,KY, {hor_ellipsis} reactions systematically, covering the wide energy and kinematic regions. The analysis is pursued with a dynamical coupled-channels (DCC) model, the EBAC-DCC model, within which the unitarity among relevant meson-baryon channels, including the three-body {pi}{pi}N channel, is fully taken into account.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Cavity QED with an ultracold ensemble on a chip: Prospects for strong magnetic coupling at finite temperatures
We study the nonlinear dynamics of an ensemble of cold trapped atoms with a hyperfine transition magnetically coupled to a resonant microwave cavity mode. Despite the minute single-atom coupling, one obtains strong coupling between collective hyperfine qubits and microwave photons, enabling coherent transfer of an excitation between the long-lived atomic qubit state and the mode. Evidence of strong coupling can be obtained from the cavity transmission spectrum even at finite thermal photon number. The system makes it possible to study further prominent collective phenomena such as superradiant decay of an inverted ensemble or the building of a narrowband stripline micromaser locked to an atomic hyperfine transition.
74 ATOMIC AND MOLECULAR PHYSICS↗
Intrinsic bulk viscosity of the one-component plasma
The intrinsic bulk viscosity of the one-component plasma (OCP) is computed and analyzed using equilibrium molecular dynamics simulations and the Green-Kubo formalism. It is found that bulk viscosity exhibits a maximum at Γ ≈ 1, corresponding to the condition that the average kinetic energy of particles equals the potential energy at the average interparticle spacing. The weakly coupled and strongly coupled limits are analyzed and used to construct a model that captures the full range of coupling strengths simulated: Γ ≈ 10 –2 –10 2 . Simulations are also run of the Yukawa one-component plasma (YOCP) in order to understand the impact of electron screening. It is found that electron screening leads to a smaller bulk viscosity due to a reduction in the excess heat capacity of the system. Bulk viscosity is shown to be at least an order of magnitude smaller than shear viscosity in both the OCP and YOCP. The generalized frequency-dependent bulk viscosity coefficient is also analyzed. This is found to exhibit a peak near twice the plasma frequency in strongly coupled conditions, which is associated with the oscillatory decay observed in the bulk viscosity autocorrelation function. As a result, the generalized shear and bulk viscosity coefficients are found to have a similar magnitude for ω ≳ 2ω p at strongly coupled conditions.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Investigating SU(3) with Nf=8 fundamental fermions at strong renormalized coupling
Lattice simulations have observed a novel strong coupling symmetric mass generation (SMG) phase for the SU(3) gauge system with $N_f=8$ fundamental fermions (represented by two sets of staggered fields) at very large renormalized coupling ($g^2_{GF} \gtrsim 25$). The results of Phys.Rev.D 106 (2022) 014513 suggest that the SMG phase is separated from the weak coupling, conformal phase by a continuous phase transition, implying that the SMG phase exists in the continuum limit. To scrutinize these findings, we are generating a set of large volume zero temperature ensembles using nHYP improved staggered fermions with additional Pauli-Villars fields to tame gauge field fluctuations. We consider the low-lying meson spectrum and verify the existence of the SMG phase. Based on a finite size scaling analysis we predict that the phase transition between the strong and weak coupling phases is likely governed by a merged fixed point that is ultraviolet in the strong coupling but infrared in the weak coupling side. This finding suggests that the SU(3) 8-flavor system sits at the opening of the conformal window
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Non-Abelian duality and confinement: From N = 2 to N = 1 supersymmetric QCD
Not Available
Shifman, M.↗
Strong Coulomb coupling influences ion and neutral temperatures in atmospheric pressure plasmas
Molecular dynamics simulations are used to model ion and neutral temperature evolution in partially-ionized atmospheric pressure plasma at different ionization fractions. Results show that ion–ion interactions are strongly coupled at ionization fractions as low as 10 –5 and that the temperature evolution is influenced by effects associated with the strong coupling. Specifically, disorder-induced heating is found to rapidly heat ions on a timescale of the ion plasma period (~10 s ps) after an ionization pulse. This is followed by the collisional relaxation of ions and neutrals, which cools ions and heats neutrals on a longer (~ns) timescale. Slight heating then occurs over a much longer (~100 s ns) timescale due to ion-neutral three-body recombination. An analytic model of the temperature evolution is developed that agrees with the simulation results. Finally, a conclusion is that strong coupling effects are important in atmospheric pressure plasmas.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Influences of Quantum Mechanically Mixed Electronic and Vibrational Pigment States in 2D Electronic Spectra of Photosynthetic Systems: Strong Electronic Coupling Cases
In 2D electronic spectroscopy studies, long-lived quantum beats have recently been observed in photosynthetic systems, and several theoretical studies have suggested that the beats are produced by quantum mechanically mixed electronic and vibrational states. Concerning the electronic-vibrational quantum mixtures, the impact of protein-induced fluctuations was examined by calculating the 2D electronic spectra of a weakly coupled dimer with the Franck-Condon active vibrational modes in the resonant condition. This analysis demonstrated that quantum mixtures of the vibronic resonance are rather robust under the influence of the fluctuations at cryogenic temperatures, whereas the mixtures are eradicated by the fluctuations at physiological temperatures. However, this conclusion cannot be generalized because the magnitude of the coupling inducing the quantum mixtures is proportional to the inter-pigment electronic coupling. In this paper, we explore the impact of the fluctuations on electronic-vibrational quantum mixtures in a strongly coupled dimer with an off-resonant vibrational mode. Toward this end, we calculate energy transfer dynamics and 2D electronic spectra of a model dimer that corresponds to the most strongly coupled bacteriochlorophyll molecules in the Fenna-Matthews-Olson complex in a numerically accurate manner. The quantum mixtures are found to be robust under the exposure of protein-induced fluctuations at cryogenic temperatures, irrespective of the resonance. At 300 K, however, the quantum mixing is disturbed more strongly by the fluctuations, and therefore, the beats in the 2D spectra become obscure even in a strongly coupled dimer with a resonant vibrational mode. Further, the overall behaviors of the energy transfer dynamics are demonstrated to be dominated by the environment and coupling between the 0 0 vibronic transitions as long as the Huang-Rhys factor of the vibrational mode is small. Finally, the electronic-vibrational quantum mixtures do not necessarily play a significant role in electronic energy transfer dynamics despite contributing to the enhancement of long-lived quantum beating in the 2D spectra.
2D electronic spectra↗
Strong environmental coupling in a Josephson parametric amplifier
We present a lumped-element Josephson parametric amplifier designed to operate with strong coupling to the environment. In this regime, we observe broadband frequency dependent amplification with multi-peaked gain profiles. We account for this behavior using the “pumpistor” model which allows for frequency dependent variation of the external impedance. Using this understanding, we demonstrate control over the complexity of gain profiles through added variation in the environment impedance at a given frequency. With strong coupling to a suitable external impedance, we observe a significant increase in dynamic range, and large amplification bandwidth up to 700 MHz giving near quantum-limited performance.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Transport Properties of Magnetized High-Energy Density Plasma (Final Project Report)
This report summarizes results of project DE-SC0016159 "Transport Properties of Magnetized High-Energy-Density Plasma,'' which ran from 7/15/2016 - 7/14/2021. The primary objectives of the work, as stated in the original proposal, were to develop a theory that describes transport coefficients in magnetized high energy density plasmas and to test the theory with molecular dynamics (MD) simulations. The science challenge is that strong ion coupling, strong magnetization of electrons, and partial degeneracy of electrons, cause the system to be in a regime that is not well described by current theory. The particular processes that were to be investigated include: ion stopping power, diffusion, electron-ion temperature relaxation, thermal conduction and viscosity. All of the primary research objectives were accomplished during the course of this work. In addition, some unexpected results were discovered along the way that led to new and productive research directions. This work resulted in 17 publications in well-respected peer-reviewed journals (primarily Physics of Plasmas and Physical Review E), and 2 more are being prepared for publication. A few of these were selected as Editor's Picks and one was published as a Rapid Communication. Highlights of the research results include: Transport phase space: The first identification of the parameter space that defines fundamental transport regimes in terms of the Coulomb coupling and magnetization parameters. Mean force kinetic theory: Systematic derivation of a kinetic theory for strongly coupled plasmas based on a new expansion parameter of the BBGKY hierarchy. This provided the derivation of a theory that we had previously posed phenomenologically, and also revealed a new term that captures the equation of state properties at all coupling strengths. Transverse friction force: Discovery that the friction force on a test charge in a strongly magnetized plasma includes a component that is perpendicular to the motion of the test charge in the plane defined by the velocity and magnetic field vectors. Gyrofriction force: Discovery that the friction force on a test charge in a plasma that is both strongly magnetized and strongly coupled includes a component of the force in the direction of the Lorentz force. Kinetic theory for warm dense matter: Extension of the mean force kinetic theory to include partial electron degeneracy, so that it applies to warm dense matter.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Strong cooperative coupling of pressure-induced magnetic order and nematicity in FeSe
A hallmark of the iron-based superconductors is the strong coupling between magnetic, structural and electronic degrees of freedom. However, a universal picture of the normal state properties of these compounds has been confounded by recent investigations of FeSe where the nematic (structural) and magnetic transitions appear to be decoupled. Here, using synchrotron-based high-energy x-ray diffraction and time-domain Mossbauer spectroscopy, we show that nematicity and magnetism in FeSe under applied pressure are indeed strongly coupled. Distinct structural and magnetic transitions are observed for pressures between 1.0 and 1.7 GPa and merge into a single first-order transition for pressures ≳1.7 GPa, reminiscent of what has been found for the evolution of these transitions in the prototypical system Ba(Fe 1–x Co x ) 2 As 2 . Lastly, our results are consistent with a spin-driven mechanism for nematic order in FeSe and provide an important step towards a universal description of the normal state properties of the iron-based superconductors.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗