Abstract
Materials with non-trivial band topology have attracted enormous attention in recent years due to their unique physical properties and potential applications in quantum computation. After the discovery of topological insulators, many semimetals were also found to possess non-trivial band topology, such as Dirac and Weyl semimetals. To date, most of the discovered topological semimetals are materials with weak electronic correlations, so it is desirable to find topological semimetals with strong electronic correlations. In our previous work, we found that YbPtBi is a promising Kondo Weyl semimetal candidate. At high temperature, electronic structure calculations show that pairs of triply degenerate points can be found, which is supported by angle resolved photonemission spectroscopy (ARPES) measurements. In an external magnetic field, these points are split into pairs of Weyl nodes, and the presence of Weyl fermions is revealed by the angle dependent magnetotransport measurements. However, at low temperatures when the electronic structure are strongly influenced by band hybridization, the results of heat capacity measurements suggest a nodal thermal excitation, which is evidence for the presence of Weyl Kondo semimetal phase in YbPtBi. This is further supported by the observation of a topological Hall effect in Hall resistivity measurements. Here we present a study of the sample dependence of the properties of YbPtBi. The relationship between the carrier density and negative longitudinal magnetoresistance (MR) clearly suggests the presence of the chiral anomaly and can be consistently explained based on the band structure. The analysis of the Hall resistivity reveals a strong signal of an anomalous Hall effect at low temperature, which may arise from the complex Berry curvature in momentum space. These results further suggest that YbPtBi is a potential platform for studying the properties of Weyl fermions in the presence of strong electronic correlations.
Highlights
EXPERIMENTAL METHODSSingle crystals of YbPtBi were prepared using a Bi self flux
Since the discovery of topological insulators,[1,2,3] much attention has been paid to non-trivial band topology in solid state materials
Theoretical studies showed that topological semimetallic phases can appear in strongly correlated materials,[6,7] and since these can often be more readily tuned, it is proposed that these materials can be ideal platforms for studying the properties of Dirac/Weyl fermions with the presence of strong electronic correlations, and for realizing topological quantum phase transitions and other related phenomena.[6,7]
Summary
Single crystals of YbPtBi were prepared using a Bi self flux. We have presented seven samples, labeled Sa to Sg, which have different carrier densities. Note that Sg is S13 in Ref. 8, while Se corresponds to S11. For the samples Sa to Sd, the Bi-flux used for the single crystal growth was systematically reduced. To further decrease the carrier density, an increasing ratio of gold doping is used for Se to Sg with a maximum starting amount of 5%, keeping the Bi content unchanged. The magnetotransport was measured in a Quantum Design Physical Property Measurement System (PPMS) using a sample rotator and a 9 T superconducting magnet. To apply the standard four probe method for the measurements, four Pt wires were attached to the samples using silver paint
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