Signatures of the Magnetic Entropy in the Thermopower Signals in Nanoribbons of the Magnetic Weyl Semimetal Co₃Sn₂S₂

Abstract

Weyl semimetals exhibit interesting electronic properties due to their topological band structure. In particular, large anomalous Hall and anomalous Nernst signals are often reported, which allow for a detailed and quantitative study of subtle features. We pattern single crystals of the magnetic Weyl semimetal Co 3 Sn 2 S 2 into nanoribbon devices using focused ion beam cutting and optical lithography. This approach enables a very precise study of the galvano-and thermomagnetic transport properties. Indeed, we found interesting features in the temperature dependency of the anomalous Hall and Nernst effects. We present an analysis of the data based on the Mott relation and identify in the Nernst response signatures of magnetic fluctuations enhancing the anomalous Nernst conductivity at the magnetic phase transition.

Generic Seebeck effect from spin entropy

“…35 Thermoelectricity enhancement recently found in some magnetic ion-doped semiconductors [36][37][38] may share the same origins, yielding a practical way to further optimize current thermoelectric materials. Likewise, a spin-entropy contribution is also expected in transverse thermoelectricity, i.e., the Nernst effect, as recently discussed for a magnetic semimetal Co 3 Sn 2 S 2 by Geishendorf et al 39 Unlike MnSi, the transport and static spin entropy may generally deviate from a quantitative scaling because the magnetic d bands may not be the only active bands responsible for transport, or are rather localized as in a magnetic insulator. In the latter case, a m may reduce to zero despite a large S m .…”

Cubic Hafnium Nitride: A Novel Topological Semimetal Hosting a 0-Dimensional (0-D) Nodal Point and a 1-D Topological Nodal Ring

“…For nodal point semimetals, the most studied members among them are Weyl and Dirac semimetals. Weyl semimetals (Hosur and Qi, 2013;Soluyanov et al, 2015;Zheng et al, 2016;Lin et al, 2017;Zhang M. et al, 2018;Bedoyapinto et al, 2020;Geishendorf et al, 2020;Thakur et al, 2020) possess twofold degenerate 0-D Weyl nodes, which are protected by inversion (P) or time-reversal (T) symmetries. However, Dirac semimetals (Chen et al, 2015;Gong et al, 2017;Yuan et al, 2017;Zhang X. et al, 2018;Jing and Heine, 2019) host quadruple-degenerate 0-D Dirac points, and these massless Dirac points are protected by the crystalline symmetry.…”

On the Onsager-Casimir reciprocal relations in a tilted Weyl semimetal

“…Co 3 Sn 2 S 2 is a magnetic Weyl semimetal [14][15][16]. The interplay of band topology and magnetism gives rise to a number of unusual phenomena, attracting intensive research interest [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. A very recent experiment has uncovered a chirality-dependent Hall effect that is antisymmetric in both the in-plane magnetic field and the magnetization [11].…”