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Giant anomalous Nernst effect and quantum-critical scaling in a ferromagnetic semimetal
Sakai A.a,b, Mizuta Y.P.c,d, Nugroho A.A.a,e, Sihombing R.a,e, Koretsune T.b,d, Suzuki M.-T.b,d, Takemori N.d, Ishii R.a, Nishio-Hamane D.a, Arita R.b,d, Goswami P.f,g, Nakatsuji S.a,b
a Institute for Solid State Physics, University of Tokyo, Kashiwa, Japan
b CREST, Japan Science and Technology Agency (JST), Kawaguchi, Japan
c Faculty of Mathematics and Physics, Kanazawa University, Kanazawa, Japan
d Center for Emergent Matter Science (CEMS), RIKEN, Hirosawa, Wako, Japan
e Faculty of Mathematics and Natural Sciences, Bandung Institute of Technology, Bandung, Indonesia
f Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, United States
g Department of Physics and Astronomy, Northwestern University, Evanston, United States
[vc_row][vc_column][vc_row_inner][vc_column_inner][vc_separator css=”.vc_custom_1624529070653{padding-top: 30px !important;padding-bottom: 30px !important;}”][/vc_column_inner][/vc_row_inner][vc_row_inner layout=”boxed”][vc_column_inner width=”3/4″ css=”.vc_custom_1624695412187{border-right-width: 1px !important;border-right-color: #dddddd !important;border-right-style: solid !important;border-radius: 1px !important;}”][vc_empty_space][megatron_heading title=”Abstract” size=”size-sm” text_align=”text-left”][vc_column_text]© 2018, The Author(s). In conducting ferromagnets, an anomalous Nernst effect—the generation of an electric voltage perpendicular to both the magnetization and an applied temperature gradient—can be driven by the nontrivial geometric structure, or Berry curvature, of the wavefunction of the electrons 1,2 . Here, we report the observation of a giant anomalous Nernst effect at room temperature in the full-Heusler ferromagnet Co 2 MnGa, an order of magnitude larger than the previous maximum value reported for a magnetic conductor 3,4 . Our numerical and analytical calculations indicate that the proximity to a quantum Lifshitz transition between type-I and type-II magnetic Weyl fermions 5–7 is responsible for the observed –Tlog(T) behaviour, with T denoting the temperature, and the enhanced value of the transverse thermoelectric conductivity. The temperature dependence of the thermoelectric response in experiments and numerical calculations can be understood in terms of a quantum critical-scaling function predicted by the low-energy effective theory over more than a decade of temperatures. Moreover, the observation of an unsaturated positive longitudinal magnetoconductance, or chiral anomaly 8–10 , also provides evidence for the existence of Weyl fermions 11,12 in Co 2 MnGa.[/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”Author keywords” size=”size-sm” text_align=”text-left”][vc_column_text]Analytical calculation,Geometric structure,Lifshitz transition,Magnetic conductors,Numerical calculation,Quantum critical scaling,Temperature dependence,Thermoelectric response[/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”Indexed keywords” size=”size-sm” text_align=”text-left”][vc_column_text][/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”Funding details” size=”size-sm” text_align=”text-left”][vc_column_text]This work was supported by CREST (JPMJCR15Q5) by Japan Science and Technology Agency, by Grants-in-Aid for Scientific Research (grant numbers 16H02209, 25707030), by Grants-in-Aid for Scientific Research on Innovative Areas “J-Physics” (grant numbers 15H05882 and 15H05883) and Program for Advancing Strategic International Networks to Accelerate the Circulation of Talented Researchers (grant number R2604) from the Japanese Society for the Promotion of Science. P.G. was supported by JQI-NSF-PFC and LPS-MPO-CMTC (at the University of Maryland) and start-up funds from the Northwestern University. The use of the facilities of the Materials Design and Characterization Laboratory at the Institute for Solid State Physics is appreciated.[/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”DOI” size=”size-sm” text_align=”text-left”][vc_column_text]https://doi.org/10.1038/s41567-018-0225-6[/vc_column_text][/vc_column_inner][vc_column_inner width=”1/4″][vc_column_text]Widget Plumx[/vc_column_text][/vc_column_inner][/vc_row_inner][/vc_column][/vc_row][vc_row][vc_column][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][/vc_column][/vc_row]