1,812 research outputs found
Physical phase space of lattice Yang-Mills theory and the moduli space of flat connections on a Riemann surface
It is shown that the physical phase space of \g-deformed Hamiltonian
lattice Yang-Mills theory, which was recently proposed in refs.[1,2], coincides
as a Poisson manifold with the moduli space of flat connections on a Riemann
surface with handles and therefore with the physical phase space of
the corresponding -dimensional Chern-Simons model, where and are
correspondingly a total number of links and vertices of the lattice. The
deformation parameter \g is identified with and is an
integer entering the Chern-Simons action.Comment: 12 pages, latex, no figure
Nuclear Polarization in Quantum Point Contacts in an In-Plane Magnetic Field
Nuclear spin polarization is typically generated in GaAs quantum point
contacts (QPCs) when an out-of-plane magnetic field gives rise to
spin-polarized quantum Hall edge states, and a voltage bias drives transitions
between the edge states via electron-nuclear flip-flop scattering. Here, we
report a similar effect for QPCs in an in-plane magnetic field, where currents
are spin polarized but edge states are not formed. The nuclear polarization
gives rise to hysteresis in the d.c. transport characteristics, with relaxation
timescales around 100 seconds. The dependence of anomalous QPC conductance
features on nuclear polarization provides a useful test of their
spin-sensitivity.Comment: 5 page
Computational Design of Flexible Electride with Nontrivial Band Topology
Electrides, with their excess electrons distributed in crystal cavities playing the role of anions, exhibit a variety of unique electronic and magnetic properties. In this work, we employ the first-principles crystal structure prediction to identify a new prototype of A3B electride in which both interlayer spacings and intralayer vacancies provide channels to accommodate the excess electrons in the crystal. This A3B type of structure is calculated to be thermodynamically stable for two alkaline metals oxides (Rb3O and K3O). Remarkably, the unique feature of multiple types of cavities makes the spatial arrangement of anionic electrons highly flexible via elastic strain engineering and chemical substitution, in contrast to the previously reported electrides characterized by a single topology of interstitial electrons. More importantly, our first-principles calculations reveal that Rb3O is a topological Dirac nodal line semimetal, which is induced by the band inversion at the general electronic k momentums in the Brillouin zone associated with the intersitial electric charges. The discovery of flexible electride in combining with topological electronic properties opens an avenue for electride design and shows great promises in electronic device applications
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