Knight shift and spin-echo decay time of YBa{sub 2}Cu{sub 4}O{sub 8} and YBa{sub 2}Cu{sub 3}O{sub 7} in the superconducting state

Journal Article · Fri Mar 01 04:00:00 EST 1996 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.53.5915· OSTI ID:282821

Pines, D; Wrobel, P ^[1]

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1. University of Illinois at Urbana-Champaign, Department of Physics, Loomis Laboratory of Physics, 1110 West Green Street, Urbana, Illinois 61801 (United States)

We report on calculations of the Knight shift and spin-echo decay time, {ital T}{sub 2{ital G}}, in the superconducting state which are based on a nearly antiferromagnetic Fermi-liquid description of the spin-fluctuation spectrum, in which a single spin component is responsible for the dynamic spin behavior and the magnetic interaction between the planar quasiparticles brings the system close to antiferromagnetic behavior. The dynamic spin susceptibility is described by a random-phase-approximation-like expression, with a restoring force which is unchanged from the normal state, and an irreducible particle-hole susceptibility which reflects the {ital d}{sub {ital x}{sup 2}{minus}{ital y}{sup 2}} symmetry of the gap parameter and a quasiparticle Fermi surface consistent with photoemission experiments. We obtain a quantitative fit to the Knight shift results for YBa{sub 2}Cu{sub 4}O{sub 8} with a {ital d}{sub {ital x}{sup 2}{minus}{ital y}{sup 2}} strong coupling gap of maximum magnitude 2.8{ital k}{sub {ital BT}}{sub {ital c}}, and show that quantitative agreement with the recent measurements of {ital T}{sub 2{ital G}} by Corey {ital et al}. may be obtained with this {ital d}{sub {ital x}{sup 2}-{ital y}{sup 2}} pairing state and a quite substantial antiferromagnetic enhancement ({approximately}140) of the static {open_quote}{open_quote}band structure{close_quote}{close_quote} spin susceptibility at wave vectors in the vicinity of {bold Q}=({pi},{pi}). We demonstrate that the experimental results of Corey {ital et al}. rule out an anisotropic {ital s}-wave state. Analogous calculations for the Knight shift of YBa{sub 2}Cu{sub 3}O{sub 7} suggest that the {ital d}{sub {ital x}{sup 2}-{ital y}{sup 2}} strong coupling gap possesses a maximum magnitude, 2.6{ital k}{sub {ital BT}}{sub {ital c}}, and on this basis, we predict a reduction in {ital T}{sup -1}{sub 2{ital G}} of some 5% for the smaller antiferromagnetic enhancement ({approximately}38) expected for this system.

• OSTI ID: 282821
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 9 Vol. 53; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ANTIFERROMAGNETISM
BARIUM OXIDES
COPPER OXIDES
ENERGY GAP
HIGH-TC SUPERCONDUCTORS
KNIGHT SHIFT
MAGNETIC SUSCEPTIBILITY
S WAVES
SPIN ECHO
STRONG-COUPLING MODEL
YTTRIUM OXIDES