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Title: Hybridization gap and dual nature of the heavy-fermion compound UPd 2Al 3 via quasiparticle scattering spectroscopy

Abstract

We present results from point-contact spectroscopy of the antiferromagnetic heavy-fermion superconductor UPd 2Al 3 : Conductance spectra are taken from single crystals with two major surface orientations as a function of temperature and magnetic field and analyzed using a theory of cotunneling into an Anderson lattice. Spectroscopic signatures are clearly identified, including the distinct asymmetric double-peak structure arising from the opening of a hybridization gap when a coherent heavy-Fermi liquid is formed. Both the hybridization gap, found to be 7.2 ± 0.3 meV at 4 K, and the conductance enhancement above a flat background decrease upon increasing temperature. While the hybridization gap is extrapolated to remain finite up to ~28 K, close to the temperature around which the magnetic susceptibility displays a broad peak, the conductance enhancement vanishes at ~18 K, slightly above the antiferromagnetic transition temperature (T N ≈ 14 K) . This rapid decrease of the conductance enhancement is understood as a consequence of the junction drifting away from the ballistic regime due to increased scattering off magnons associated with the localized U 5 f electrons. This shows that while the hybridization gap opening is not directly associated with the antiferromagnetic ordering, its visibility in the conductance ismore » greatly affected by the temperature-dependent magnetic excitations. Our findings are not only consistent with the 5 f dual-nature picture in the literature but also shed new light on the interplay between the itinerant and localized electrons in UPd 2Al 3 .« less

Authors:
 [1];  [2];  [2];  [2];  [3]; ORCiD logo [3]; ORCiD logo [3]; ORCiD logo [3];  [2]
  1. Illinois Wesleyan Univ., Bloomington, IL (United States); Univ. of Illinois, Urbana-Champaign, IL (United States). Dept. of Physics and Materials Research Lab.
  2. Univ. of Illinois, Urbana-Champaign, IL (United States). Dept. of Physics and Materials Research Lab.
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Science (SC). Basic Energy Sciences (BES) (SC-22); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1369187
Alternate Identifier(s):
OSTI ID: 1351928
Report Number(s):
LA-UR-16-28194
Journal ID: ISSN 2469-9950; TRN: US1702655
Grant/Contract Number:
AC52-06NA25396
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 95; Journal Issue: 16; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY

Citation Formats

Jaggi, N. K., Mehio, O., Dwyer, M., Greene, L. H., Baumbach, Ryan E., Tobash, Paul H., Bauer, Eric Dietzgen, Thompson, Joe David, and Park, W. K.. Hybridization gap and dual nature of the heavy-fermion compound UPd2Al3 via quasiparticle scattering spectroscopy. United States: N. p., 2017. Web. doi:10.1103/PhysRevB.95.165123.
Jaggi, N. K., Mehio, O., Dwyer, M., Greene, L. H., Baumbach, Ryan E., Tobash, Paul H., Bauer, Eric Dietzgen, Thompson, Joe David, & Park, W. K.. Hybridization gap and dual nature of the heavy-fermion compound UPd2Al3 via quasiparticle scattering spectroscopy. United States. doi:10.1103/PhysRevB.95.165123.
Jaggi, N. K., Mehio, O., Dwyer, M., Greene, L. H., Baumbach, Ryan E., Tobash, Paul H., Bauer, Eric Dietzgen, Thompson, Joe David, and Park, W. K.. Mon . "Hybridization gap and dual nature of the heavy-fermion compound UPd2Al3 via quasiparticle scattering spectroscopy". United States. doi:10.1103/PhysRevB.95.165123. https://www.osti.gov/servlets/purl/1369187.
@article{osti_1369187,
title = {Hybridization gap and dual nature of the heavy-fermion compound UPd2Al3 via quasiparticle scattering spectroscopy},
author = {Jaggi, N. K. and Mehio, O. and Dwyer, M. and Greene, L. H. and Baumbach, Ryan E. and Tobash, Paul H. and Bauer, Eric Dietzgen and Thompson, Joe David and Park, W. K.},
abstractNote = {We present results from point-contact spectroscopy of the antiferromagnetic heavy-fermion superconductor UPd2Al3 : Conductance spectra are taken from single crystals with two major surface orientations as a function of temperature and magnetic field and analyzed using a theory of cotunneling into an Anderson lattice. Spectroscopic signatures are clearly identified, including the distinct asymmetric double-peak structure arising from the opening of a hybridization gap when a coherent heavy-Fermi liquid is formed. Both the hybridization gap, found to be 7.2 ± 0.3 meV at 4 K, and the conductance enhancement above a flat background decrease upon increasing temperature. While the hybridization gap is extrapolated to remain finite up to ~28 K, close to the temperature around which the magnetic susceptibility displays a broad peak, the conductance enhancement vanishes at ~18 K, slightly above the antiferromagnetic transition temperature (T N ≈ 14 K) . This rapid decrease of the conductance enhancement is understood as a consequence of the junction drifting away from the ballistic regime due to increased scattering off magnons associated with the localized U 5 f electrons. This shows that while the hybridization gap opening is not directly associated with the antiferromagnetic ordering, its visibility in the conductance is greatly affected by the temperature-dependent magnetic excitations. Our findings are not only consistent with the 5 f dual-nature picture in the literature but also shed new light on the interplay between the itinerant and localized electrons in UPd2Al3 .},
doi = {10.1103/PhysRevB.95.165123},
journal = {Physical Review B},
number = 16,
volume = 95,
place = {United States},
year = {Mon Apr 17 00:00:00 EDT 2017},
month = {Mon Apr 17 00:00:00 EDT 2017}
}

Journal Article:
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  • We have performed neutron critical scattering experiments on the heavy-fermion superconductor UPd{sub 2}Al{sub 3} above the N{acute e}el temperature in order to characterize the short-ranged correlations associated with the magnetic ordering. The magnetic correlation length along the hexagonal {ital c} axis is longer than that in the basal plane, suggesting that the antiferromagnetic interaction along the {ital c} axis is stronger than the ferromagnetic one in the basal plane. This antiferromagnetic correlation is discussed in connection with the pairing mechanism of the superconductivity. We also find that the magnetic fluctuations exhibit the two-length scales reminiscent of features observed in Tbmore » and Ho. {copyright} {ital 1996 The American Physical Society.}« less
  • The temperature dependence of the Hall resistivity of thin epitaxial UPd[sub 2]Al[sub 3] films with low defect densities is investigated. It shows a minimum at 6 K for fields up to 12 T. This feature is attributed to the superposition of a coherence-derived low-temperature Hall coefficient and a skew-scattering contribution. Further implications on the Hall effect in the coherence regime of Kondo lattices are discussed.
  • The authors report experimental results of electrical resistivity, de Haas-van Alphen effect, specific heat and thermal expansion of UPd{sub 2}Al{sub 3}. The nominal composition is denoted by the formula of UPd{sub 2+x}Al{sub 3+y}. Samples with the composition of UPd{sub 2}Al{sub 3.03} and UPd{sub 2.02}Al{sub 3.03} reveal de Haas-van Alphen oscillations of the magnetic susceptibility. An anomaly is observed in the superconducting phase in the temperature dependence of the specific heat and thermal expansion of UPd{sub 2}Al{sub 3.03}. The relation between the sample quality and the appearance of the anomaly is discussed.
  • We present bulk properties (resistivity, specific heat, and susceptibility) of the quasiternary system UPd{sub 2}(Al{sub 1{minus}x}Ga{sub x}){sub 3} and derive the superconducting and magnetic phase diagrams. For low Ga substitution (x{le}0.25) a complete suppression of superconductivity is found, while the magnetic properties are hardly affected. For larger x the magnetic transition temperature T{sub N} gradually decreases, and the mass enhancement of the electrons increases, until at x=0.8{endash}0.9 a crystallographic transition takes place from the PrNi{sub 2}Al{sub 3} to the BaB{sub 2}Pt{sub 3} lattice. At the structural transition T{sub N} discontinuously increases, while the electronic specific heat {gamma} grows smoothly throughmore » the transition. We discuss the relationship between the alloying parameter x and the magnetic ordering and electronic hybridization, respectively. The strong suppression of the superconductivity in UPd{sub 2}Al{sub 3} with Ga suggests an unconventional mechanism of superconductivity, most probably related to spin fluctuations mediating the pairing. {copyright} {ital 1997} {ital The American Physical Society}« less