KCo 2 As 2 : A new portal for the physics of high-purity metals

Journal Article · Fri Jul 01 00:00:00 UTC 2022 · Physical Review Materials

DOI: https://doi.org/10.1103/physrevmaterials.6.075001 · OSTI ID:1874806

Pandey, Abhishek  ^[1]; Liu, Y.  ^[2]; Samal, Saroj L. ^[3]; Kushnirenko, Yevhen ^[4]; Kaminski, A. ^[4]; Singh, David Joseph  ^[5]; Johnston, David C.  ^[4]

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1. Ames Lab., and Iowa State Univ., Ames, IA (United States); Univ. of the Witwatersrand, Johannesburg (South Africa)
2. Ames Lab., and Iowa State Univ., Ames, IA (United States); Ecole Polytechnique Federale Lausanne (EPFL) (Switzerland)
3. Ames Lab., and Iowa State Univ., Ames, IA (United States); National Institute of Technology, Rourkela (India)
4. Ames Lab., and Iowa State Univ., Ames, IA (United States)
5. Univ. of Missouri, Columbia, MO (United States)

High-quality single crystals of KCo₂As₂ with the body-centered tetragonal ThCr₂Si₂ structure were grown using KAs self flux. Structural, magnetic, thermal, and electrical transport properties were investigated. No clear evidence for any phase transitions was found in the temperature range 2–300 K. The in-plane electrical resistivity ρ versus temperature T is highly unusual, showing a T⁴ behavior below 30 K and an anomalous positive curvature up to 300 K, which is different from the linear behavior expected from the Bloch-Grüneisen theory for electron scattering by acoustic phonons. This positive curvature has been previously observed in the in-plane resistivity of high-conductivity layered delafossites such as PdCoO₂ and PtCoO₂. The in-plane ρ(T → 0) = 0.36μΩ cm of KCo₂As₂ is exceptionally small for this class of compounds. The material also exhibits a magnetoresistance at low T which attains a value of about 40% at T = 2 K and magnetic field H = 80 kOe. The magnetic susceptibility χ of KCo₂As₂ is isotropic and about an order of magnitude smaller than the values for the related compounds SrCo₂As₂ and BaCo₂As₂. The χ increases above 100 K, which is found from our first-principles calculations to arise from a sharp peak in the electronic density of states just above the Fermi energy E_F. Heat capacity C_p(T) data at low T yield an electronic density of states N(E_F) that is about 36% larger than predicted by the first-principles theory. The C_p(T) data near room temperature suggest the presence of excited optic vibration modes, which may also be the source of the positive curvature in ρ(T). Angle-resolved photoemission spectroscopy measurements are compared with the theoretical predictions of the band structure and Fermi surfaces. In conclusion, our results show that KCo₂As₂ provides a new avenue for investigating the physics of high-purity metals.

• Research Organization: Ames Laboratory (AMES), Ames, IA (United States); University of Missouri, Columbia, MO (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division
• OSTI ID: 1874806
• Report Number(s): IS-J-10,839
• Journal Information: Physical Review Materials, Journal Name: Physical Review Materials Journal Issue: 7 Vol. 6; ISSN 2475-9953
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English