▎ 摘　　要

We investigate low-energy electronic states and heat capacity of graphene strips. The density of states of graphene is obtained by diagonalizing a lattice Hamiltonian for graphene strips with zigzag and armchair edges, respectively. The modes localized at strip edges in zigzag geometry reveal a peculiar density of states near the zero-energy line. We find that the overall behavior of the heat capacity C-el(T) in graphene is similar to that of a two-level system, and the low-temperature heat capacity shows unconventional behavior of C-el proportional to T-alpha with alpha approximate to 2.2 varying slightly for different choices of various band structure parameters and the width of the strip. Unusual strong enhancement is observed in the heat capacity at low temperatures for zigzag strips, in addition to the T-alpha behavior of the two-dimensional graphene. This enhancement stems from the states localized along the edges in the strips with zigzag terminations.