Large spin Hall and spin Nernst effects in Dirac nodal line semimetals XCuYAs (X=Zr, Hf; Y=Si, Ge)

Babu Baijnath Prasad^1,2*, Guang-Yu Guo^1,3

¹Department of Physics and Center for Theoretical Physics, National Taiwan University, Taipei 10617, Taiwan
²Nano Science and Technology Program, Taiwan International Graduate Program, Academia Sinica, Taipei 11529, Taiwan
³Physics Division, National Center for Theoretical Sciences, Hsinchu 30013, Taiwan

* Presenter:Babu Baijnath Prasad, email:babubaijnathprasad@gmail.com

XCuYAs (X=Zr, Hf; Y= Si, Ge) compounds have unique physical properties ranging from p-type transparent semiconductors to iron-based superconductors. So, we have studied the electronic structure, spin Hall and spin Nernst effects in these compounds based on DFT calculations. First, we have found the nonsymmorphic symmetry-protected Dirac line nodes along the Brillouin zone boundary A-M and X-R for the XCuYAs compounds having low density of states near the Fermi level. Second, the spin Hall and spin Nernst conductivities in some of these compounds are found to be large, e.g., the SHC and SNC (at room temperature) of HfCuGeAs are found to be as large as -514 (ћ/e)(S/cm) and -0.73 (ћ/e)(A/m-K), respectively. Also, the magnitude and sign of the SHC and SNC can be tuned via changing either applied electric field direction, spin current direction or by chemical doping or gating. A detailed analysis of the band-decomposed and k-resolved spin Berry curvatures reveals the origin of the such large values of SHC and SNC among these set of materials. Spin-orbit coupling gapped Dirac points near the Fermi level as well as gapless Dirac line nodes are the main source of origin for the XCuYAs compounds in exhibiting large spin Hall and spin Nernst conductivities which makes it a suitable candidate for the possible applications in spintronics and spin caloritronics.

Reference :-
1. Babu Baijnath Prasad and Guang-Yu Guo*, Tunable spin Hall and spin Nernst effects in Dirac line-node semimetals XCuYAs (X=Zr, Hf; Y=Si, Ge); arXiv:2007.15303 (2020).

Keywords: First-principles calculations, Electronic structure, Topological materials, spin Hall effect, spin Nernst effect