Active forces in confluent cell monolayers
Activity pulses induce spontaneous flow reversals in viscoelastic environments
An active torque dipole across tissue layers drives avian left-right symmetry breaking
An ideal Weyl semimetal induced by magnetic exchange
Abstract:
Weyl semimetals exhibit exceptional quantum electronic transport due to the presence of topologically-protected band crossings called Weyl nodes. The nodes come in pairs with opposite chirality, but their number and location in momentum space is otherwise material specific. Following the initial discoveries there is now a need for better material realizations, ideally comprising a single pair of Weyl nodes located at or very close to the Fermi level and in an energy window free from other overlapping bands. Here we propose the layered intermetallic EuCd$_2$As$_2$ to be such a system. We show that Weyl nodes in EuCd$_2$As$_2$ are magnetically-induced via exchange coupling, emerging when the Eu spins are aligned by a small external magnetic field. The identification of EuCd$_2$As$_2$ as a model magnetic Weyl semimetal, evidenced here by ab initio calculations, photoemission spectroscopy, quantum oscillations and anomalous Hall transport measurements, opens the door to fundamental tests of Weyl physics.Anomalous gapped boundaries between surface topological orders in higher-order topological insulators and superconductors with inversion symmetry
Physical Review B: Condensed Matter and Materials Physics American Physical Society