Seminar: Thermo-Spin Transport in Spin Gapless Semiconductor and Weyl Semi-Metal Heusler Alloys

Hari Srikanth

Distinguished University Professor

Florida Institute for Emergent Low-Dimensional Quantum Materials (FIELD-QM)

Department of Physics, University of South Florida, Tampa, FL USA

Humboldt Visiting Professor, AG Farle, Physics Department, University of Duisburg-Essen

Heusler alloy-based spin gapless semiconductors (SGS) with very high Curie temperatures (TC) exhibit zero bandgap in one of the spin channels and a non-zero bandgap in the other spin channel, making them a promising class of materials for tunable spin transport. Our group has recently reported the first experimental observation of Anomalous Nernst Effect (ANE) in polycrystalline quaternary Heusler CoFeCrGa [1] as well as thin films grown on MgO substrates [2]. The results reveal that the ANE originates from asymmetric skew-scattering of charge carriers and the thin films show ANE coefficients nearly two orders of magnitude higher and comparable to that of Weyl semimetal Co2MnGa thin films. In quaternary Heusler Weyl semimetals CoFeVSb, our experiments combining magneto-thermal transport, RF transverse susceptibility and FMR have revealed fascinating topological aspects and the dominance of intrinsic Berry phase due to the presence of Weyl points predicted by DFT calculations [3]. Finally, we present for the first time a novel degree of freedom in the control of macroscopic magnetic properties in Co2MnGa via the modulation of the intrinsic properties of Weyl nodes through structural distortions [3]. Overall, this talk would present key aspects of thermally driven spin currents in Heusler alloys.

“Emergence of asymmetric skew-scattering dominated anomalous Nernst effect in spin gapless semiconductors Co1+xFe1-xCrGa” - Amit Chanda, Deepika Rani, Jadupati Nag, Aftab Alam, KG Suresh, Manh-Huong Phan, Hari Srikanth, Phys. Rev. B 106, 134416(2022)

2.      “Large thermo-spin effects in Heusler alloy-based spin gapless semiconductor thin films” -A. Chanda, Deepika Rani, D. DeTellem, N. Alzahrani, D. A. Arena, S. Witanachchi, Ratnamala Chatterjee, M.H. Phan and Hari Srikanth, ACS Applied Materials & Interfaces15, 53697 (2023)

3.      “Structural manipulation of Weyl nodes in Co2MnGa” -N. Schulz, G. Pantano, D. DeTellem, A. Changa, E. Clements, M. McGuire, A. Markou, C. Felser, D.A. Arena, J. Gayles, M.H. Phan and Hari Srikanth, Advanced Materials (under review, 2024)