Nernst Effect of High-Mobility Weyl Electrons in NdAlSi Enhanced by a Fermi Surface Nesting Instability
R. Yamada, Takuya Nomoto, Atsushi Miyake, Toshihiro Terakawa, Akiko Kikkawa, Ryotaro Arita, Masashi Tokunaga, Y. Taguchi, Yoshinori Tokura, Max Hirschberger
Abstract
The thermoelectric Nernst effect of solids converts heat flow to beneficial electronic voltages. Here, using a correlated topological semimetal with high carrier mobility <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>μ</a:mi></a:math> in the presence of magnetic fluctuations, we demonstrate an enhancement of the Nernst effect close to a magnetic phase transition. A magnetic instability in NdAlSi modifies the carrier relaxation time on “hot spots” in momentum space, causing a strong band filling dependence of <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>μ</c:mi></c:math>. We quantitatively derive electronic band parameters from a novel two-band analysis of the Nernst effect <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mrow><e:msub><e:mi>S</e:mi><e:mrow><e:mi>x</e:mi><e:mi>y</e:mi></e:mrow></e:msub></e:mrow></e:math>, in good agreement with quantum oscillation measurements and band calculations. While the Nernst response of NdAlSi behaves much like conventional semimetals at high temperatures, an additional contribution <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mrow><g:mi mathvariant="normal">Δ</g:mi><g:msub><g:mi>S</g:mi><g:mrow><g:mi>xy</g:mi></g:mrow></g:msub></g:mrow></g:math> from electronic correlations appears just above the magnetic transition. Our work demonstrates the engineering of the relaxation time, or the momentum-dependent self-energy, to generate a large Nernst response independent of a material’s carrier density, i.e., for metals, semimetals, and semiconductors with large <j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline"><j:mi>μ</j:mi></j:math>. Published by the American Physical Society 2024