Three-Dimensional Topological Insulator in a Magnetic Field: Chiral Side Surface States and Quantized Hall Conductance

Low energy excitation of surface states of a three-dimensional topological insulator (3DTI) can be described by Dirac fermions. By using a tight-binding model, the transport properties of the surface states in a uniform magnetic field is investigated. It is found that chiral surface states parallel to the magnetic field are responsible to the quantized Hall (QH) conductance $(2n+1)\frac{e^2}{h}$ multiplied by the number of Dirac cones. Due to the two-dimension (2D) nature of the surface states, the robustness of the QH conductance against impurity scattering is determined by the oddness and evenness of the Dirac cone number. An experimental setup for transport measurement is proposed

Case Study – Ground Failures and Ruptures in Xian City

Xian city, the most well known ancient city of China for her incredible Terra Cotta Warriers and so forth, has been suffered from ground fracture for years. Surface ruptures and faultings encountered in strips all over the city. Hundreds of buildings were severely destroyed and many of them even have been demolished. Ground failures wide-spread and enlarged from time to time, especially right from Tangshan earthquake of July 28, 1976. Therefore serious concerns and suspicious of being associated with major earthquakes have arosed. Thus it has been a problem of both engineering and social influence. Like many other cities in China and even in the world such as Houston, Texas, USA, surface faulting or surface rupture often caused many guess-works and arguments among different engineers, geologists and seismologists. In turn, many projects either underway or co be undertaken will be seriously lagged out due to discrepancies of different assessment and measures of mitigation. The authors have been deeply involved in surface faulting and ruptures as a background for exploring the mechanism and predicting its possible effects from the engineering point of view. In this paper, the authors introduce their systematic ease study on Xian ground failures towards this end, including site investigations, typical damages assessment, numerical analysis on fracture mechanism, model tests in laboratory and comprehensive evaluations etc. Conclusions were drawn not only for this particular ancient city but also provided a referential real ease for the like in the world