skip to main content

Title: Migdal–Eliashberg superconductivity in a Kondo lattice

We apply the Migdal–Eliashberg theory of superconductivity to heavy-fermion and mixed valence materials. Specifically, we extend the Anderson lattice model to a case when there exists a strong coupling between itinerant electrons and lattice vibrations. Using the saddle-point approximation, we derive a set of coupled nonlinear equations which describe competition between the crossover to a heavy-fermion or mixed-valence regimes and conventional superconductivity. We find that superconductivity at strong coupling emerges on par with the development of the many-body coherence in a Kondo lattice. Superconductivity is gradually suppressed with the onset of the Kondo screening and for strong electron-phonon coupling the Kondo screening exhibits a characteristic re-entrant behavior. Even though for both weak and strong coupling limits the suppression of superconductivity is weaker in the mixed-valence regime compared to the local moment one, superconducting critical temperature still remains nonzero. In the weak coupling limit the onset of the many body coherence develops gradually, in the strong coupling limit it emerges abruptly in the mixed valence regime while in the local moment regime thef-electrons remain effectively decoupled from the conduction electrons. Possibility of experimental realization of these effects in Ce-based compounds is also discussed.

more » « less
Author(s) / Creator(s):
Publisher / Repository:
IOP Publishing
Date Published:
Journal Name:
Journal of Physics: Condensed Matter
Medium: X Size: Article No. 325602
Article No. 325602
Sponsoring Org:
National Science Foundation
More Like this
  1. The Kondo lattice is one of the classic examples of strongly correlated electronic systems. We conduct a controlled study of the Kondo lattice in one dimension, highlighting the role of excitations created by the composite fermion operator. Using time-dependent matrix product state methods, we compute various correlation functions and contrast them with both large-N mean-field theory and the strong-coupling expansion. We show that the composite fermion operator creates long-lived, charge-e and spin-1/2 excitations, which cover the low-lying single-particle excitation spectrum of the system. Furthermore, spin excitations can be thought to be composed of such fractionalized quasiparticles with a residual interaction which tend to disappear at weak Kondo coupling.

    <supplementary-material><permissions><copyright-statement>Published by the American Physical Society</copyright-statement><copyright-year>2024</copyright-year></permissions></supplementary-material></sec> </div> <a href='#' class='show open-abstract' style='margin-left:10px;'>more »</a> <a href='#' class='hide close-abstract' style='margin-left:10px;'>« less</a> </div><div class="clearfix"></div> </div> </li> <li> <div class="article item document" itemscope itemtype=""> <div class="item-info"> <div class="title"> <a href="" itemprop="url"> <span class='span-link' itemprop="name">Symmetry of magnetic correlations in spin-triplet superconductor UTe2</span> </a> </div> <div> <strong> <a class="misc external-link" href="" target="_blank" title="Link to document DOI">  <span class="fas fa-external-link-alt"></span></a> </strong> </div> <div class="metadata"> <span class="authors"> <span class="author" itemprop="author">Butch, Nicholas P.</span> <span class="sep">; </span><span class="author" itemprop="author">Ran, Sheng</span> <span class="sep">; </span><span class="author" itemprop="author">Saha, Shanta R.</span> <span class="sep">; </span><span class="author" itemprop="author">Neves, Paul M.</span> <span class="sep">; </span><span class="author" itemprop="author">Zic, Mark P.</span> <span class="sep">; </span><span class="author" itemprop="author">Paglione, Johnpierre</span> <span class="sep">; </span><span class="author" itemprop="author">Gladchenko, Sergiy</span> <span class="sep">; </span><span class="author" itemprop="author">Ye, Qiang</span> <span class="sep">; </span><span class="author" itemprop="author">Rodriguez-Rivera, Jose A.</span> </span> <span class="year">( <time itemprop="datePublished" datetime="2022-04-05">April 2022</time> , npj Quantum Materials) </span> </div> <div style="cursor: pointer;-webkit-line-clamp: 5;" class="abstract" itemprop="description"> <title>Abstract

    The temperature dependence of the low-energy magnetic excitations in the spin-triplet superconductor UTe2was measured via inelastic neutron scattering in the normal and superconducting states. These excitations have a peak instensity at 4 meV, follow the Brillouin zone edges near the crystallographic b-axis, obey the paramagnetic structural symmetry, and track the temperature evolution of the heavy fermion bulk magnetic susceptibility. Thus, the imaginary part of the dynamic susceptibility follows the behavior of interband correlations in a hybridized Kondo lattice with an appropriate characteristic energy. These excitations are a lower-dimensional analog of phenomena observed in other Kondo lattice materials, such that their presence is not necessarily due to dominance of ferromagnetic or antiferromagnetic correlations. The onset of superconductivity alters the magnetic excitations noticeably on the same energy scales, suggesting that these changes originate from additional electronic structure modification.

    more » « less
  2. Novel electronic phenomena frequently form in heavy-fermions because of the mutual localized and itinerant nature of f -electrons. On the magnetically ordered side of the heavy-fermion phase diagram, f -moments are expected to be localized and decoupled from the Fermi surface. It remains ambiguous whether Kondo lattice can develop inside the magnetically ordered phase. Using spectroscopic imaging with scanning tunneling microscope, complemented by neutron scattering, x-ray absorption spectroscopy, and dynamical mean field theory, we probe the electronic states in antiferromagnetic USb 2 . We visualize a large gap in the antiferromagnetic phase within which Kondo hybridization develops below ~80 K. Our calculations indicate the antiferromagnetism and Kondo lattice to reside predominantly on different f -orbitals, promoting orbital selectivity as a new conception into how these phenomena coexist in heavy-fermions. Finally, at 45 K, we find a novel first order–like transition through abrupt emergence of nontrivial 5 f -electronic states that may resemble the “hidden-order” phase of URu 2 Si 2 . 
    more » « less
  3. Lisesivdin, Sefer Bora (Ed.)

    In this work, a new canonical transformation for the Anderson lattice Hamiltonian with f–f electron coupling was developed, which was further used to identify a new Kondo lattice Hamiltonian. Different from the single impurity Kondo effect, the resulted new Kondo lattice Hamiltonian only includes the spin-flip scattering processes between conduction electrons and f-electrons, while the normal process of non-spin-flip scattering is absent in this Hamiltonian, under the second order approximation. The new Kondo lattice Hamiltonian may be used to study some anomalous physical properties in some Kondo lattice intermetallic compounds.

    more » « less
  4. Abstract

    Two-dimensional (2D) metals can host gapless plasmonic excitations that strongly couple to electrons and thus may significantly affect superconductivity. To investigate the dynamical interplay of the electron–electron and electron–phonon interactions in the theory of 2D superconductivity, we apply a full momentum- and frequency-dependent one-loop theory treating electron–phonon, electron–plasmon, and phonon–plasmon coupling with the same accuracy. We tune the strength of the Coulomb interaction by varying the external screeningεextto the layered superconductor and find three distinct regions. At weak screening, superconductivity is mediated by plasmons. In the opposite limit conventional electron–phonon interactions dominate. In between, we find a suppressed superconducting state. Our results show that even in conventional electron–phonon coupled layered materials, superconductivity can be significantly enhanced by the electron–plasmon coupling in a manner that can be controlled by the external screening.

    more » « less