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Title: Crystallographic, electronic, thermal, and magnetic properties of single-crystal SrCo 2As 2

In tetragonal SrCo 2As 2 single crystals, inelastic neutron scattering measurements demonstrated that strong stripe-type antiferromagnetic (AFM) correlations occur at a temperature T = 5 K [W. Jayasekara et al., arXiv:1306.5174] that are the same as in the isostructural AFe 2As 2 (A = Ca, Sr, Ba) parent compounds of high-T c superconductors. This surprising discovery suggests that SrCo 2As 2 may also be a good parent compound for high-T c superconductivity. Here, structural and thermal expansion, electrical resistivity ρ, angle-resolved photoemission spectroscopy (ARPES), heat capacity C p, magnetic susceptibility χ, 75As NMR and neutron diffraction measurements of SrCo 2As 2 crystals are reported together with LDA band structure calculations that shed further light on this fascinating material. The c-axis thermal expansion coefficient α c is negative from 7 to 300 K, whereas α a is positive over this T range. The ρ(T) shows metallic character. The ARPES measurements and band theory confirm the metallic character and in addition show the presence of a flat band near the Fermi energy E F. The band calculations exhibit an extremely sharp peak in the density of states D(E F) arising from a flat d x2-y2 band. A comparison of the Sommerfeld coefficientmore » of the electronic specific heat with χ(T → 0) suggests the presence of strong ferromagnetic itinerant spin correlations which on the basis of the Stoner criterion predicts that SrCo 2As 2 should be an itinerant ferromagnet, in conflict with the magnetization data. The χ(T) does have a large magnitude, but also exhibits a broad maximum at 115 K suggestive of dynamic short-range AFM spin correlations, in agreement with the neutron scattering data. The measurements show no evidence for any type of phase transition between 1.3 and 300 K and we propose that metallic SrCo 2As 2 has a gapless quantum spin-liquid ground state.« less
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [1] ;  [1] ;  [3] ;  [4] ;  [5] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1]
  1. Ames Lab. and Iowa State Univ., Ames, IA (United States). Dept. of Physics and Astronomy
  2. Ames Lab. and Iowa State Univ., Ames, IA (United States). Dept. of Physics and Astronomy; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  3. Univ. of Missouri, Columbia, MO (United States). Missouri Research Reactor
  4. State Univ. of New York (SUNY), Plattsburgh, NY (United States)
  5. Russian Academy of Sciences, Urals Div., Ekaterinburg (Russian Federation). Inst. of Metal Physics
Publication Date:
Grant/Contract Number:
AC02-07CH11358
Type:
Accepted Manuscript
Journal Name:
Physical Review. B, Condensed Matter and Materials Physics
Additional Journal Information:
Journal Volume: 88; Journal Issue: 1; Journal ID: ISSN 1098-0121
Publisher:
American Physical Society (APS)
Research Org:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
OSTI Identifier:
1127239