Topic
Quadrupole
About: Quadrupole is a research topic. Over the lifetime, 14614 publications have been published within this topic receiving 261495 citations. The topic is also known as: quadrapole & electric quadrupole.
Papers published on a yearly basis
Papers
More filters
TL;DR: In this paper, a review of available information on molecular quadrupole and higher moments is presented and a theorem is proved which shows that only one independent scalar quantity is required to determine a molecular electric multipole tensor of rank p for molecules with an n-fold axis of symmetry where p < n.
Abstract: A summary and critical review of available information on molecular quadrupole and higher moments is presented. A theorem is also proved which shows that only one independent scalar quantity is required to determine a molecular electric multipole tensor of rank p for molecules with an n-fold axis of symmetry where p < n.
733 citations
TL;DR: This work demonstrates experimentally a member of this predicted class of materials—a quantized quadrupole topological insulator—produced using a gigahertz-frequency reconfigurable microwave circuit, and provides conclusive evidence of a unique form of robustness against disorder and deformation, which is characteristic of higher-order topologicalinsulators.
Abstract: The theory of electric polarization in crystals defines the dipole moment of an insulator in terms of a Berry phase (geometric phase) associated with its electronic ground state. This concept not only solves the long-standing puzzle of how to calculate dipole moments in crystals, but also explains topological band structures in insulators and superconductors, including the quantum anomalous Hall insulator and the quantum spin Hall insulator, as well as quantized adiabatic pumping processes. A recent theoretical study has extended the Berry phase framework to also account for higher electric multipole moments, revealing the existence of higher-order topological phases that have not previously been observed. Here we demonstrate experimentally a member of this predicted class of materials-a quantized quadrupole topological insulator-produced using a gigahertz-frequency reconfigurable microwave circuit. We confirm the non-trivial topological phase using spectroscopic measurements and by identifying corner states that result from the bulk topology. In addition, we test the critical prediction that these corner states are protected by the topology of the bulk, and are not due to surface artefacts, by deforming the edges of the crystal lattice from the topological to the trivial regime. Our results provide conclusive evidence of a unique form of robustness against disorder and deformation, which is characteristic of higher-order topological insulators.
701 citations
TL;DR: Equal efficiencies can be reached simultaneously by adapting z-filter principles to MQMAS and to decrease dispersion signals in order to enhance the resolution using zNMR.
694 citations
01 Jan 1987
TL;DR: In this article, the reduced electric quadrupole transition probability, B(E2)up-arrow, from the ground state to the first-excited 2/sup +/ state of even-even nuclides are given in Table I.
Abstract: Adopted values for the reduced electric quadrupole transition probability, B(E2)up-arrow, from the ground state to the first-excited 2/sup +/ state of even-even nuclides are given in Table I. Values of tau, the mean life of the 2/sup +/ state, E, the energy, and ..beta../sub 2/, the quadrupole deformation parameter, are also listed there. The ratio of ..beta../sub 2/ to the value expected from the single-particle model is presented. The intrinsic quadrupole moment, Q/sub O/, is deduced from the B(E2)up-arrow value. The product E x B(E2)up-arrow is expressed as a precentage of the energy-weighted total and isoscalar E2 sum-rule strengths.
670 citations