J. K. Freericks

Georgetown University

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Alexander F. Kemper

North Carolina State University

Thomas Devereaux

SLAC National Accelerator Laboratory

V. Zlatić

University of Split

A. M. Shvaika

Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine

H. R. Krishnamurthy

Indian Institute of Science Bangalore

Brian Moritz

SLAC National Accelerator Laboratory

Mark Jarrell

Marshall University

Volodymyr Turkowski

University of Central Florida

Michael A. Sentef

Max Planck Institute for the Structure and Dynamics of Matter

Karlis Mikelsons

NOAA Center for Satellite Applications and Research

Cooperative Institutions

Georgetown University

National Institute of Standards and Technology

Lawrence Berkeley National Laboratory

University of Maryland, College Park

Argonne National Laboratory

University of Colorado Boulder

Joint Quantum Institute

Joint Institute for Laboratory Astrophysics

Oak Ridge National Laboratory

Stanford University

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Thouless energy as a unifying concept for Josephson junctions tuned through the Mott metal-insulator transition

Physical Review B (2006)

A. N. Tahvildar-Zadeh J. K. Freericks Branislav K. Nikolić

The Thouless energy was introduced in the 1970s as a semiclassical energy for electrons diffusing through a finite-sized conductor. It turns out to be an important quantum-mechanical energy scale for many systems ranging from disordered metals to quantum chaos to quantum chromodynamics. In particular, it has been quite successful in describing the properties of Josephson junctions when the barrier is a diffusive normal-state metal. The Thouless energy concept can be generalized to insulating barriers by extracting an energy scale from the two-probe Kubo conductance of a strongly correlated electron system (metallic or insulating) via a generalized definition of the quantum-mechanical level spacing to many-body systems. This energy scale is known to determine the crossover from tunneling to Ohmic (thermally activated) transport in normal tunnel junctions. Here we use it to illustrate how the quasiclassical picture of transport in Josephson junctions is modified as the strongly correlated barrier passes through the Mott transition. Surprisingly, we find the quasiclassical form holds well beyond its putative realm of validity.

Semiclassical physics

Mott insulator

Quantum wire

Kubo formula

10.1103/physrevb.73.184515

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Citations (7)

What do the two times in two-time correlation functions mean for interpreting tr-ARPES?

Journal of Electron Spectroscopy and Related Phenomena (2021)

J. K. Freericks Alexander F. Kemper

Response time

10.1016/j.elspec.2021.147104

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Examining Electron-Boson Coupling Using Time-Resolved Spectroscopy

Physical Review X (2013)

Michael A. Sentef Alexander F. Kemper Brian Moritz J. K. Freericks Zhi‐Xun Shen

Pump-probe spectroscopy based on ultrashort laser pulses is gaining a surging interest as a method for probing electronic dynamics in solid-state materials. But how to make sense of the spectroscopic measurements remains a fundamental challenge. Theorists now report a timely development of a concrete and general understanding of pump-probe spectroscopy studies of electron-phonon coupling.

Electron spectroscopy

10.1103/physrevx.3.041033

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Nonconstant electronic density of states tunneling inversion for A15 superconductors:Nb3Sn

Physical review. B, Condensed matter (2002)

J. K. Freericks Amy Liu Alexander Quandt J. Geerk

We reexamine the tunneling data on A15 superconductors by performing a generalized McMillan-Rowell tunneling inversion that incorporates a nonconstant electronic density of states obtained from band-structure calculations. For ${\mathrm{Nb}}_{3}\mathrm{Sn},$ we find that the fit to the experimental data can be slightly improved by taking into account the sharp structure in the density of states, but it is likely that such an analysis alone is not enough to explain completely the superconducting tunneling characteristics of this material. Nevertheless, the extracted Eliashberg function displays a number of features expected to be present for the highest-quality ${\mathrm{Nb}}_{3}\mathrm{Sn}$ samples.

Density of states

10.1103/physrevb.65.224510

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Relaxation of nonequilibrium populations after a pump: the breaking of Mathiessen's rule

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2017)

J. K. Freericks Omadillo Abdurazakov Alexander F. Kemper

From the early days of many-body physics, it was realized that the self-energy governs the relaxation or lifetime of the retarded Green's function. So it seems reasonable to directly extend those results into the nonequilibrium domain. But experiments and calculations of the response of quantum materials to a pump show that the relationship between the relaxation and the self-energy only holds in special cases. Experimentally, the decay time for a population to relax back to equilibrium and the linewidth measured in a linear-response angle-resolved photoemission spectroscopy differ by large amounts. Theoretically, aside from the weak-coupling regime where the relationship holds, one also finds deviations and additionally one sees violations of Mathiessen's rule. In this work, we examine whether looking at an effective transport relaxation time helps to analyze the decay times of excited populations as they relax back to equilibrium. We conclude that it may do a little better, but it has a fitting parameter for the overall scale which must be determined.

10.1117/12.2261872

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Citations (1)

Theoretical description of time‐resolved pump/probe photoemission in TaS₂: a single‐band DFT+DMFT(NRG) study within the quasiequilibrium approximation

physica status solidi (b) (2009)

J. K. Freericks H. R. Krishnamurthy Yizhi Ge Amy Liu Th. Pruschke

In this work, we theoretically examine recent pump/probe photoemission experiments on the strongly correlated charge-density-wave insulator TaS\_2. We describe the general nonequilibrium many-body formulation of time-resolved photoemission in the sudden approximation, and then solve the problem using dynamical mean-field theory with the numerical renormalization group and a bare density of states calculated from density functional theory including the charge-density-wave distortion of the ion cores and spin-orbit coupling We find a number of interesting results: (i) the bare band structure actually has more dispersion in the perpendicular direction than in the two-dimensional planes; (ii) the DMFT approach can produce upper and lower Hubbard bands that resemble those in the experiment, but the upper bands will overlap in energy with other higher energy bands; (iii) the effect of the finite width of the probe pulse is minimal on the shape of the photoemission spectra; and (iv) the quasiequilibrium approximation does not fully describe the behavior in this system.

10.1002/pssb.200881555

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Citations (33)

Computational projects with the Landau-Zener problem in the quantum mechanics classroom

arXiv (Cornell University) (2023)

Livia A. J. Guttieres Marko D. Petrović J. K. Freericks

The Landau-Zener problem, where a minimum energy separation is passed with constant rate in a two-state quantum-mechanical system, is an excellent model quantum system for a computational project. It requires a low-level computational effort, but has a number of complex numerical and algorithmic issues that can be resolved through dedicated work. It can be used to teach computational concepts such as accuracy, discretization, and extrapolation, and it reinforces quantum concepts of time-evolution via a time-ordered product and of extrapolation to infinite time via time-dependent perturbation theory. In addition, we discuss the concept of compression algorithms, which are employed in many advanced quantum computing strategies, and easy to illustrate with the Landau-Zener problem.

10.48550/arxiv.2306.11633

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Nonequilibrium electron and lattice dynamics of strongly correlated Bi ₂ Sr ₂ CaCu ₂ O _8+δ single crystals

Science Advances (2018)

Tatiana Konstantinova J. D. Rameau Alexander H. Reid Omadillo Abdurazakov Lijun Wu

The interplay between the electronic and lattice degrees of freedom in nonequilibrium states of strongly correlated systems has been debated for decades. Although progress has been made in establishing a hierarchy of electronic interactions with the use of time-resolved techniques, the role of the phonons often remains in dispute, a situation highlighting the need for tools that directly probe the lattice. We present the first combined megaelectron volt ultrafast electron diffraction and time- and angle-resolved photoemission spectroscopy study of optimally doped Bi2Sr2CaCu2O8+δ. Quantitative analysis of the lattice and electron subsystems' dynamics provides a unified picture of nonequilibrium electron-phonon interactions in the cuprates beyond the N-temperature model. The work provides new insights on the specific phonon branches involved in the nonequilibrium heat dissipation from the high-energy Cu-O bond stretching "hot" phonons to the lowest-energy acoustic phonons with correlated atomic motion along the <110> crystal directions and their characteristic time scales. It reveals a highly nonthermal phonon population during the first several picoseconds after the photoexcitation. The approach, taking advantage of the distinct nature of electrons and photons as probes, is applicable for studying energy relaxation in other strongly correlated electron systems.

Lattice (music)

10.1126/sciadv.aap7427

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Citations (67)

Focus on conceptual ideas in quantum mechanics for teacher training

arXiv (Cornell University) (2023)

J. K. Freericks

In this work, we describe strategies and provide case-study activities that can be used to examine the properties of superposition, entanglement, tagging, complementarity, and measurement in quantum curricula geared for teacher training. Having a solid foundation in these conceptual ideas is critical for educators who will be adopting quantum ideas within the classroom. Yet they are some of the most difficult concepts to master. We show how one can systematically develop these conceptual foundations with thought experiments on light and with thought experiments that employ the Stern-Gerlach experiment. We emphasize the importance of computer animations in aiding the instruction on these concepts.

Complementarity (molecular biology)

Stern

Conceptual Change

Conceptual framework

Foundation (evidence)

10.48550/arxiv.2305.01108

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First-principles determination of superconducting properties of metals

Physica B Condensed Matter (2000)

J. K. Freericks Sven P. Rudin Amy Liu

Superconducting transition temperature

BCS theory

10.1016/s0921-4526(99)01994-8

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Citations (4)