2,877 research outputs found
Metallization and Spin Fluctuations in Cu-doped Lead Apatite
An electronic structure and magnetic properties analysis of the recently
proposed Cu-doped lead apatite is performed. We show that electronic structures
of differently Cu-substituted structures are characterized by localized
molecular Cu-O bands at or near the Fermi level. The Cu substitutions can
happen at both Pb1 and Pb2 sites, leading to metallic and semiconducting states
differently. The electronic states in these bands are highly unstable
magnetically and form clusters of rigidly ferromagnetically coupled magnetic
moments on Cu and neighboring oxygen atoms with a total moment of about 1
. The ground state of uniformly Cu-doped lead apatite appears to be
magnetic and semiconducting. The non-uniform distribution of two Cu atoms at
the nearest Pb2 sites leads to an antiferromagnetic semiconducting state with
formation energy close to uniformly distributed Cu configurations. The
inclusion of quantum spin fluctuations confirms the stability of magnetic Cu-O
clusters. Our calculations revealed the absence of the long-range magnetic
order between uniformly distributed Cu-O clusters, creating the spin glass type
of system
Local Cyber-physical Attack with Leveraging Detection in Smart Grid
A well-designed attack in the power system can cause an initial failure and
then results in large-scale cascade failure. Several works have discussed power
system attack through false data injection, line-maintaining attack, and
line-removing attack. However, the existing methods need to continuously attack
the system for a long time, and, unfortunately, the performance cannot be
guaranteed if the system states vary. To overcome this issue, we consider a new
type of attack strategy called combinational attack which masks a line-outage
at one position but misleads the control center on line outage at another
position. Therefore, the topology information in the control center is
interfered by our attack. We also offer a procedure of selecting the vulnerable
lines of its kind. The proposed method can effectively and continuously deceive
the control center in identifying the actual position of line-outage. The
system under attack will be exposed to increasing risks as the attack
continuously. Simulation results validate the efficiency of the proposed attack
strategy.Comment: Accepted by IEEE SmartGridComm 201
Coexistence of type-II Dirac point and weak topological phase in Pt 3 Sn
Intriguing topological phases may appear in both insulating and semimetallic states. Topological insulators exhibit topologically nontrivial band inversion, while topological Dirac/Weyl semimetals show “relativistic” linear band crossings. Here, we report an unusual topological state of Pt3Sn, where the two topological features appear simultaneously. Based on first-principles calculations, we show that Pt3Sn is a three-dimensional weak topological semimetal with topologically nontrivial band inversion between the valence and conduction bands, where the band structure also possesses type-II Dirac points at the boundary of two electron pockets. The formation of the Dirac points can be understood in terms of the representations of relevant symmetry groups and the compatibility relations. The topological surface states appear in accordance with the nontrivial bulk band topology. The unique coexistence of the two distinct topological features in Pt3Sn enlarges the material scope in topological physics, and is potentially useful for spintronics
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