Time-Linear Quantum Transport Simulations with Correlated Nonequilibrium Green's Functions

We present a time-linear scaling method to simulate open and correlated quantum systems out of equilibrium. The method inherits from many-body perturbation theory the possibility to choose selectively the most relevant scattering processes in the dynamics, thereby paving the way to the real-time characterization of correlated ultrafast phenomena in quantum transport. The open system dynamics is described in terms of an "embedding correlator" from which the time-dependent current can be calculated using the Meir-Wingreen formula. We show how to efficiently implement our approach through a simple grafting into recently proposed time-linear Green's function methods for closed systems. Electron-electron and electron-phonon interactions can be treated on equal footing while preserving all fundamental conservation laws.

Real-Time GW: Toward an Ab Initio Description of the Ultrafast Carrier and Exciton Dynamics in Two-Dimensional Materials

We demonstrate the feasibility of the time-linear scaling formulation of the GW method [Phys. Rev. Lett. 124, 076601 (2020)PRLTAO0031-900710.1103/PhysRevLett.124.076601] for ab initio simulations of optically driven two-dimensional materials. The time-dependent GW equations are derived and solved numerically in the basis of Bloch states. We address carrier multiplication and relaxation in photoexcited graphene and find deviations from the typical exponential behavior predicted by the Markovian Boltzmann approach. For a resonantly pumped semiconductor we discover a self-sustained screening cascade leading to the Mott transition of coherent excitons. Our results draw attention to the importance of non-Markovian and dynamical screening effects in out-of-equilibrium phenomena.

Floquet Topological Phase of Nondriven p-Wave Nonequilibrium Excitonic Insulators

The nontrivial topology of p-wave superfluids makes these systems attractive candidates in information technology. In this work we report on the topological state of a p-wave nonequilibrium excitonic insulator (NEQ-EI) and show how to steer a nontopological band insulator with bright p excitons toward this state by a suitable laser pulse, thus achieving a dynamical topological phase transition. The underlying mechanism behind the transition is the broken gauge-symmetry of the NEQ-EI which causes self-sustained persistent oscillations of the excitonic condensate and hence a Floquet topological state for high enough exciton densities. We show the formation of Floquet Majorana modes at the boundaries of the open system and discuss unique topological spectral signatures for time-resolved ARPES experiments. We emphasize that the topological properties of a p-wave NEQ-EI arise exclusively from the electron-hole Coulomb interaction as the system is not driven by external fields.

Ultrafast Quantum Interference in the Charge Migration of Tryptophan

Extreme-ultraviolet-induced charge migration in biorelevant molecules is a fundamental step in the complex path leading to photodamage. In this work we propose a simple interpretation of the charge migration recently observed in an attosecond pump-probe experiment on the amino acid tryptophan. We find that the decay of the prominent low-frequency spectral structure with increasing pump-probe delay is due to a quantum beating between two geometrically distinct, almost degenerate charge oscillations. Quantum beating is ubiquitous in these systems, and at least on the few-to-tens of femtosecond time scales, it may dominate over decoherence the line intensities of time-resolved spectra. We also address the experimentally observed phase shift in the charge oscillations of two different amino acids, tryptophan and phenylalanine. Our results indicate that a beyond mean-field treatment of the electron dynamics is necessary to reproduce the correct behavior.

CHEERS: a tool for correlated hole-electron evolution from real-time simulations

We put forward a practical nonequilibrium Green's function (NEGF) scheme to perform real-time evolutions of many-body interacting systems driven out of equilibrium by external fields. CHEERS is a computational tool to solve the NEGF equation of motion in the so called generalized Kadanoff-Baym ansatz and it can be used for model systems as well as first-principles Hamiltonians. Dynamical correlation (or memory) effects are added to the Hartree-Fock dynamics through a many-body self-energy. Applications to time-dependent quantum transport, time-resolved photoabsorption and other ultrafast phenomena are discussed.

Ultrafast Charge Migration in XUV Photoexcited Phenylalanine: A First-Principles Study Based on Real-Time Nonequilibrium Green's Functions

The early-stage density oscillations of the electronic charge in molecules irradiated by an attosecond XUV pulse takes place on femto- or subfemtosecond time scales. This ultrafast charge migration process is a central topic in attoscience because it dictates the relaxation pathways of the molecular structure. A predictive quantum theory of ultrafast charge migration should incorporate the atomistic details of the molecule, electronic correlations, and the multitude of ionization channels activated by the broad-bandwidth XUV pulse. We propose a first-principles nonequilibrium Green's function method fulfilling all three requirements and apply it to a recent experiment on the photoexcited phenylalanine amino acid. Our results show that dynamical correlations are necessary for a quantitative overall agreement with the experimental data. In particular, we are able to capture the transient oscillations at frequencies 0.15 and 0.30 PHz in the hole density of the amine group as well as their suppression and the concomitant development of a new oscillation at frequency 0.25 PHz after ∼14 fs.

Dynamical formation and manipulation of Majorana fermions in driven quantum wires in contact with a superconductor

Controlling the dynamics of Majorana fermions (MF) subject to time-varying driving fields is of fundamental importance for the practical realization of topological quantum computing. In this work we study how it is possible to dynamically generate and maintain the topological phase in cold-atom nanowires after the temporal variation of the Hamiltonian parameters. Remarkably we show that for a sudden quench the system can never relax toward a state exhibiting fully developed MF, independently of the initial and final Hamiltonians. Only for sufficiently slow protocols the system behaves adiabatically, and the topological phase can be reached. Finally we address the crucial question of how "adiabatic" a protocol must be in order to manipulate the MF inside the topological phase without deteriorating their Majorana character.

Insight on hole-hole interaction and magnetic order from dichroic auger-photoelectron coincidence spectra

The absence of sharp structures in the Auger line shapes of partially filled bands has severely limited the use of electron spectroscopy in magnetic crystals and other correlated materials. By a novel interplay of experimental and theoretical techniques we achieve a combined understanding of the photoelectron, Auger, and Auger-photoelectron coincidence spectra (APECS) of the antiferromagnetic CoO. A recently discovered dichroic effect in angle resolved (DEAR) APECS reveals a complex pattern in the Auger line shape, which is here explained in detail, labeling the final states by their total spin. Since the dichroic effect exists in the antiferromagnetic state but vanishes at the Néel temperature, the DEAR-APECS technique detects the phase transition from its local effects, thus providing a unique tool to observe and understand magnetic correlations where the usual methods are not applicable.

Correlation-induced memory effects in transport properties of low-dimensional systems

We demonstrate the remnant presence of initial correlations in the steady-state electrical current jS flowing between low-dimensional interacting leads. The leads are described as Luttinger liquids and electrons can tunnel via a quantum point contact. We derive an analytic result for the time-dependent current and show that ground-state correlations have a large impact on the relaxation and long-time behavior. In particular, the I-V characteristic is not reproduced by quenching the interaction in time. We further present a universal formula of jS for an arbitrary sequence of interaction quenches and it is established that jS is history dependent for nonsmooth switching process.

Unconventional quasiparticle lifetime in graphene

We address the question of how large can the lifetime of electronic states be at low energies in graphene, below the scale of the optical phonon modes. For this purpose, we study the many-body effects at the K point of the spectrum, which induce a strong coupling between electron-hole pairs and out-of-plane phonons. We show the existence of a soft branch of hybrid states below the electron-hole continuum when graphene is close to the charge neutrality point, leading to an inverse lifetime proportional to the cube of the quasiparticle energy. This implies that a crossover should be observed in transport properties, from such a slow decay rate to the lower bound given at very low energies by the decay into acoustic phonons.

The fibrinolytic system components are increased in systemic sclerosis and modulated by Alprostadil (alpha1 ciclodestryn)

OBJECTIVES

To evaluate urokinase plasminogen activator (u-PA), urokinase plasminogen activator soluble receptor (su-PAR), plasminogen activator inhibitor 1 (PAI-1) and tissue plasminogen activator (t-PA) plasma levels in SSc patients (pts) versus healthy controls and their modulation by intravenous alphacyclodestrine (Alprostadil).

METHODS

Plasma levels of u-PA, su-PAR, PAI-1 and t-PA were measured in 40 SSc (34 lSSc and 6 dSSc) pts and in 30 healthy controls. In SSc, blood was drawn before and after 3 consecutive daily of Alprostadil infusion (60 mg in 250 cc NaCl 0.9%).

RESULTS

In SSc su-PAR basal levels were higher than controls (7.48 +/- 2.5 vs 4.69 +/- 0.4 ng/ml; p = 0.001) and were significantly reduced by Alprostadil (5.93 +/- 1.7; p = 0.002), but remain higher than controls (p = 0.03). u-PA basal levels were higher than controls (3.78 +/- 1.5 vs 1.29 +/- 0.3 ng/ml; p < 0.001) and were reduced by Alprostadil (2.39 +/- 1.7; p < 0.001) to control levels. SSc PAI-1 basal levels were lower than controls (31.60 +/- 7.7 vs 48.30 +/- 6.8 ng/ml; p < 0.001) and increased by Alprostadil (34.66 +/- 5.4; p = 0.04), but lower than controls (p < 0.001). SSc t-PA basal levels were higher in respect to controls (1645.81 +/- 792.7 vs 571.95 +/- 75.5 pg/ml; p < 0.0001) and reduced by Alprostadil (1318.06 +/- 603.5; p = 0.04), but still higher than controls (p = 0.001).

CONCLUSION

Fibrinolysis were increased in SSc. Infusions of Alprostadil modulate u-PA, su-PAR, PAI-1 and t-PA, restoring near normal levels. In SSc, fibrinolysis system may become a potential target for new therapies.

An economic evaluation of the JNC hypertension guidelines using data from a randomized controlled trial. Joint National Committee

BACKGROUND

We wanted to determine the clinical cost of managing hypertension when following the Joint National Committee on Hypertension (JNC) guidelines, including drug therapy, the cost of monitoring for and treating side effects, compliance, and the cost of switching after therapeutic failures.

METHODS

The base-case analysis considers antihypertensive agents from four therapeutic classes that were recently evaluated in a large randomized trial: enalapril, amlodipine, acebutolol, and chlorthalidone. Clinical evaluation, therapy, and monitoring for hypertension are modeled with an incidence-based Markov model. Clinical inputs include agent efficacy, side effects, and compliance with dosing schedules. JNC-recommended clinical and laboratory monitoring schedules are followed for each agent. Switches between classes occur for therapeutic failures. Drug and medical care costs are valued in 1995 US dollars.

RESULTS

Although patients whose hypertension was initially treated with amlodipine achieved control more readily than patients who were given the other agents, the initial costs to achieve and maintain hypertension control were lowest for chlorthalidone ($641), followed by acebutolol ($920), amlodipine ($946), and enalapril ($948). Maintenance costs were lowest for chlorthalidone. For all agents except chlorthalidone, drug costs were the largest component of overall costs, followed by the costs of office visits, laboratory monitoring, and switching between classes for therapeutic failures.

CONCLUSIONS

By following JNC guidelines, a slightly higher percentage of patients will achieve hypertension control with a newer class calcium channel blocker (amlodipine) but at a substantially higher cost than with a generic diuretic (chlorthalidone).

Pharmaceutical sciences' manpower supply and internal rate of return

A pharmacy student has many career options upon graduation. These options include graduate education in one of the pharmaceutical sciences and a retail pharmacy position. The attractive salaries offered by chain pharmacies play an important role in the recent graduate's career decision-making process. The purpose of this study is to provide a comparative assessment of the internal rate of return (IRR) for different pharmaceutical science career options as related to chain-store pharmacist earnings. Additionally, this study analyzes the effect of the IRR on the applicant pool size and composition for graduate study in pharmaceutical sciences. Income/age profiles were developed using public domain income data derived from salary surveys sponsored by professional associations. Based on these income/age profiles, IRRs were estimated for the pharmaceutical science disciplines, clinical pharmacy, pharmaceutics, medicinal chemistry, and pharmacy administration, and further differentiated for industry versus academic careers. The IRRs are the highest for Pharm.D.'s in academic careers (16.0%), followed by pharmaceutical scientists employed by pharmaceutical industry (8.13%). The IRR of pharmaceutical scientists in academia is lower than the return of other financial investment vehicles. Other authors have established a relationship between the IRR of a profession and a rise or decline in the applicant pool. The IRRs calculated here imply that this association can also be observed for the pharmaceutical scientist applicant pool. Low IRRs should result in a declining applicant pool. However, the last decade has shown an increase of 66% in the number of Ph.D.'s granted, while the percentage of Ph.D.'s granted to nonpharmacists or non-Americans has not increased significantly over the same time period.(ABSTRACT TRUNCATED AT 250 WORDS)