Quantum oscillations, magnetic breakdown and thermal Hall effect in Co₃Sn₂S₂

Abstract

Co3Sn2S2 is a ferromagnetic semi-metal with Weyl nodes in its band structure and a large anomalous Hall effect below its Curie temperature of 177 K. We present a detailed study of its Fermi surface and examine the relevance of the anomalous transverse Wiedemann Franz law to it. We studied Shubnikov-de Haas oscillations along two orientations in single crystals with a mobility as high as cm2 V−1 s−1 subject to a magnetic field as large as ∼60 T. The angle dependence of the frequencies is comparable with density functional theory (DFT) calculations and reveals two types of hole pockets (H1, H2) and two types of electron pockets (E1, E2). An additional unexpected frequency emerges at high magnetic field. We attribute it to magnetic breakdown between the hole pocket H2 and the electron pocket E2, since it is close to the sum of the E2 and H2 fundamental frequencies. By measuring the anomalous thermal and electrical Hall conductivities, we quantified the anomalous transverse Lorenz ratio, which is close to the Sommerfeld ratio () below 100 K and deviates downwards at higher temperatures. This finite temperature deviation from the anomalous Wiedemann–Franz law is a source of information on the distance between the sources and sinks of the Berry curvature and the chemical potential.

Topological charge-entropy scaling in kagome Chern magnet TbMn6Sn6

“…In Ni and Fe, the κ A xy =σ A xy T deviates the Sommerfeld value downwards at higher temperatures due to the inelastic scattering 36,45 . A particular Berry spectrum also causes a suppressed κ A xy =σ A xy T at high temperatures in Mn 3 Ge and Co 3 Sn 2 S 2 37,46 . To the best of our knowledge, TbMn 6 Sn 6 is the first topological magnet that possesses an enhanced κ A xy =σ A xy T ratio at elevated temperatures.…”

Tuning the anomalous Nernst and Hall effects with shifting the chemical potential in Fe-dope and Ni-doped Co$_3$Sn$_2$S$_2$

“…The coexist of ferromagnetism and Kondo effect would need to be further clarified. Since k f = 44 [33] when the residual resistivity is 200 µΩcm, one can exclude Anderson localozation.…”

“…A stoichiometric ratio of Ni, Fe, Co, Sn and S powders was sealed in a quartz tube. We grew high quality single crystals of Co 3−x Ni x Sn 2 S 2 and Co 3−y Fe y Sn 2 S 2 by selfflux method as reported before [31,33]. Shiny crystals were selected by careful mechanical sep-aration after growth.…”

Exchange-biased topological transverse thermoelectric effects in a Kagome ferrimagnet

“…First, it is worth emphasizing that TbMn6Sn6 exhibits large Berry curvature mainly due to massive Dirac bands near K points. The K-point Dirac gap originates from gapping a vertical nodal line along the K-H direction [see Figure 3 Mn3Ge where the Lorenz ratio deviates above 100 K 41,50 . This is because that massive Dirac bands exhibit smoother Berry curvature variation with respect to the Fermi energy, compared to Weyl points.…”