A New Classification for Axis Dependent Conduction Polarity

ORAL

Abstract

Axis dependent thermopower polarity has been observed in metals. It is usually explained as a multi-band effect with mobility variation of two carrier. Yet the signature of a multi-band system is a large Nernst coefficient, because the Nernst coefficient in multiband systems has a term that expresses the difference between the thermopowers of the two bands. We observe the anisotropic thermopower in single-crystal NaSn2As2, with very small Nernst coefficient, ruling out the two-band explanation. Here we propose a new classification, which is a single-band induced anisotropy, due to a particular shape of the Fermi surface. This model successfully explains the anisotropic behavior of NaSn2As2. Re4Si7 is revisited, which has a positive thermopower along a, b direction and negative thermopower along c-direction. Four coefficients (thermopower, resistivity, Hall coefficient and Nernst coefficient) along 3-orientations are measured from 100 K to 400 K. The Hall coefficients along the three axes are showing the same sign and similar concentration, while the Nernst coefficients are negligibly small compared to the thermopower. This again suggests that the thermopower anisotropy of Re4Si7 should be a single-band effect.

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Presenters

  • Bin He

    Ohio State Univ - Columbus, Department of Mechanical and Aerospace Engineering, The Ohio State University

Authors

  • Bin He

    Ohio State Univ - Columbus, Department of Mechanical and Aerospace Engineering, The Ohio State University

  • Mike Scudder

    Chemistry & Biochemistry, The Ohio State University

  • Yaxian Wang

    Materials Science and Engineering, The Ohio State University, Department of Materials Science and Engineering, The Ohio State University, Materials Science and Engineering , Ohio State Univ - Columbus

  • Maxx Arguilla

    Chemistry, Massachusetts Institute of Technology, Department of Chemistry and Biochemistry, The Ohio State University

  • Nicholas Cultrara

    Chemistry & Biochemistry, The Ohio State University, Department of Chemistry and Biochemistry, The Ohio State University

  • Joshua Goldberger

    Chemistry & Biochemistry, The Ohio State University, Department of Chemistry and Biochemistry, The Ohio State University

  • Wolfgang Windl

    Materials Science and Engineering, The Ohio State University, Department of Materials Science and Engineering, The Ohio State University, Physics, Ohio State Univ - Columbus

  • Joseph P Heremans

    Mechanical and Aerospace Engineering, The Ohio State University, Mechanical and Aerospace Engineering, Ohio State Univ - Columbus, Ohio State Univ - Columbus, Department of Mechanical and Aerospace Engineering, The Ohio State University