Thermal chiral (gravitational) anomaly in antiferromagnetic topological Weyl semimetal NdAlSi

A chiral anomaly in condensed matter violates the chiral current conservation when an electric field (or thermal gradient) is applied parallel to a magnetic field. As a consequence, charge and energy pumping occurs between Weyl points of opposite chirality [1,2]. Here we report the emergence of such an effect in the antiferromagnetic Weyl semimetal NdAlSi, in which inversion as well as time-reversal symmetry are broken [3]. We observe that at low temperatures and in the high magnetic field, the electrical conductivity increases as a result of the chiral magnetic effect. Remarkably, the corresponding thermal conductivity also increases accordingly, providing experimental evidence for the thermal chiral (gravitational) anomaly in NdAlSi. Our results indicate that the chiral anomaly in Weyl semimetals significantly affects their properties on various levels.

References:

1. [1]. Vu, D., Zhang, W., Sahin, C. et al. Thermal chiral anomaly in the magnetic-field induced ideal Weyl phase of Bi_1-xSb_x. Nat. Mater. 20, 1531 (2021)
   
   [2]. Gooth, J., Niemann, A., Meng, T. et al. Experimental signatures of the mixed axial–gravitational anomaly in the Weyl semimetal NbP. Nature 547, 327 (2017).
   
   [3]. Gaudet, J., Yang, HY., Baidya, S. et al. Weyl-mediated helical magnetism in NdAlSi. Nat. Mater. 20, 1656 (2021)