Magnetoresistance from Fermi Surface Topology

Extremely large non-saturating magnetoresistance has recently been reported for a large number of both topologically trivial and non-trivial materials. Different mechanisms have been proposed to explain the observed magnetotransport properties, yet without arriving to definitive conclusions or portraying a global picture. In this work, we investigate the transverse magnetoresistance of materials by combining the Fermi surfaces calculated from first principles with the Boltzmann transport theory approach relying on the semiclassical model and the relaxation time approximation. We first consider a series of simple model Fermi surfaces to provide a didactic introduction into the charge-carrier compensation and open-orbit mechanisms leading to non-saturating magnetoresistance. We then address in detail magnetotransport in three representative materials: (i) copper, a prototypical nearly free-electron metal characterized by the open Fermi surface that results in an intricate angular magnetoresistance, (ii) bismuth, a topologically trivial semimetal in which very large magnetoresistance is known to result from charge-carrier compensation, and (iii) tungsten diphosphide WP2, a recently discovered type-II Weyl semimetal that holds the record of magnetoresistance in compounds. In all three cases our calculations show excellent agreement with both the field dependence of magnetoresistance and its anisotropy measured at low temperatures. Furthermore, the calculations allow for a full interpretation of the observed features in terms of the Fermi surface topology. These results will help addressing a number of outstanding questions, such as the role of the topological phase in the pronounced large non-saturating magnetoresistance observed in topological materials.Comment: 13 pages, 9 figure

IMPROVING THE PERFORMANCE OF DATA STREAMS IN LOSSY AND LOW-POWER NETWORKS

Presented herein are techniques to enhance the performance of data streams in Connected Grid Mesh (CG-Mesh) networks

NOVEL SECURED INTER-PERSONAL AREA NETWORK GROUP MANAGEMENT IN LOW-POWER AND LOSSY NETWORKS

Low-power and Lossy Network (LLN) environments may comprise, possibly among other things, different personal area networks (PANs) resulting in, for example, node communication challenges across or between PANs. To address these types of challenges, techniques are presented herein that support a novel secure group management method to self-solve the inter-PAN problem that is both low-cost and customer-friendly. Aspects of the techniques presented herein encompass establishing a secure node-to-node (N2N) communication link between involved inter-PAN nodes, automatically looking for the relay neighbors between different PANs (as the inter-PAN node can help with forwarding the local the Routing Protocol for LLN (RPL) messages), automatically propagating the group information and maintaining the local RPL tree between the inter-PAN nodes, etc. Aspects of the techniques presented herein employ, among other things, spreading PAN advertisement (PA) messages with group and hop information to identify a feasible routing path, using the Extensible Authentication Protocol-Tunneled Transport Layer Security (EAP-TTLS) protocol to establish a secure transport tunnel, automatically unicasting a destination-oriented directed acyclic graph (DODAG) Information Solicitation (DIS) message to join the group tree, etc. Under aspects of the techniques presented herein an application server need not know the topology of a network

AN ACCELERATED PEER-TO-PEER (P2P) COMMUNICATION METHOD FACILITATED BY REUSING EXISTING P2P PATHS FOR LOW-POWER AND LOSSY NETWORKS

The Wireless Smart Utility Networks (Wi-SUN) alliance promotes interoperable wireless standards-based solutions for Internet of Things (IoT) deployments, such as distributed automation (DA). For some applications, such as smart utility or smart city applications, it is desirable to provide optimized peer-to-peer (P2P) routing. However, for P2P traffic within a Destination Oriented Directed Acyclic Graph (DODAG), packets either have to be routed through a root in a non-storing mode or through a common ancestor in a storing mode. Techniques herein provide for locally reusing and distributing projected directed advertisement object (P-DAO) tracks. For example, when a node receives a P-DAO track from the root, the node advertises the P-DAO track to its neighbors so that they may reuse the track. Before a node sends a P-DAO request (PDR) to the root, the node first broadcasts a polling to its neighbors to look for an existing P-DAO track that can be reused