PT  - JOURNAL ARTICLE
AU  - Xiao, Meng
AU  - Ye, Liping
AU  - Qiu, Chunyin
AU  - He, Hailong
AU  - Liu, Zhengyou
AU  - Fan, Shanhui
TI  - Experimental demonstration of acoustic semimetal with topologically charged nodal surface
AID  - 10.1126/sciadv.aav2360
DP  - 2020 Feb 01
TA  - Science Advances
PG  - eaav2360
VI  - 6
IP  - 8
4099  - http://advances.sciencemag.org/content/6/8/eaav2360.short
4100  - http://advances.sciencemag.org/content/6/8/eaav2360.full
SO  - Sci Adv2020 Feb 01; 6
AB  - Weyl points are zero-dimensional band degeneracy in three-dimensional momentum space that has nonzero topological charges. The presence of the topological charges protects the degeneracy points against perturbations and enables a variety of fascinating phenomena. It is so far unclear whether such charged objects can occur in higher dimensions. Here, we introduce the concept of charged nodal surface, a two-dimensional band degeneracy surface in momentum space that is topologically charged. We provide an effective Hamiltonian for this charged nodal surface and show that such a Hamiltonian can be implemented in a tight-binding model. This is followed by an experimental realization in a phononic crystal. The measured topologically protected surface arc state of such an acoustic semimetal reproduces excellently the full-wave simulations. Creating high-dimensional charged geometric objects in momentum space promises a broad range of unexplored topological physics.