It is a conventional wisdom that the helical edge states of quantum spin Hall (QSH) insulator are particularly stable due to topological protection time-reversal symmetry. Here, we report first experimental observation an edge-dependent (pseudo-)spin effect by employing two Kekule electric circuits with molecule-zigzag and partially-bearded edges, where chirality circulating current in unit cel...

In this paper the Clar covering polynomial of a hexagonal system is introduced. In fact it is a kind of F polynomial [4] of a graph, and can be calculated by recurrence relations. We show that the number of aromatic sextets (in a Clar formula), the number of Clar formulas, the number of Kekule structures and the first Herndon number for any Kekulean hexagonal system can be easily obtained by it...

The conditions required for a formal biradical to exist in a zwitterionic form in the ground state are discussed following the recent experimental observation of zwitterionic structure in the ground state of a quinoid molecule (di-tert-butyl derivative of 2,5-diamino-1,4-benzoquinonediimine, I). A unique characteristic of molecules of this class is the fact that they may be considered as being ...

7 ABSTRACT: Vibrational frequencies can be measured and calculated with 8 high precision. Therefore, they are excellent tools for analyzing the electronic 9 structure of a molecule. In this connection, the properties of the local 10 vibrational modes of a molecule are best suited. A new procedure is described, 11 which utilizes local CC stretching force constants to derive an aromaticity 12 ind...