Topologically Charged Nodal Surface Identified with Acoustic Metacrystal 

Our new research on semimetal with topologically charged nodal surface is published in Science Advances, entitled “Experimental demonstration of acoustic semimetal with topologically charged nodal surface”.

This paper proposes, for the first time, the concept of topologically charged nodal surface, and shows that such an object can be implemented in a tight-binding model as well as a suitably designed 3D phononic crystal that works for acoustic waves. Furthermore, we have experimentally measured the acoustic analogue of “Femi-arcs” for the topologically-protected surface states, which serves as an evidence for the nonzero charge possessed by the nodal surface. Strikingly different from those well-known Weyl semimetals where the surface state arcs are pinned to the Weyl points, here the end of the arcs depend sensitively on the surface truncation of the acoustic semimetal.

Our work indicates that topologically charged objects in a band structure is not restricted to 0D, and points to abundant unexplored features of the novel phenomena associated with the topological charges such as chiral anomaly and negative magnetoresistance in condensed matter systems. 

Fig. 1. A 3D phononic crystal designed with a charged nodal surface. 

For  full text:

https://advances.sciencemag.org/content/6/8/eaav2360.abstract

May 2020