Stability of the U(1) spin liquid with spinon Fermi surface in 2+1 dimensions

We study the stability of the 2+1 dimensional U(1) spin liquid state against proliferation of instantons in the presence of spinon Fermi surface. By mapping the spinon Fermi surface into an infinite set of 1+1 dimensional chiral fermions, it is argued that an instanton has an infinite scaling dimension for any nonzero number of spinon flavors. Therefore, the spin liquid phase is stable against instantons and the non-compact U(1) gauge theory is a good low energy description.Comment: 14 pages, 7 figures, v3) minor corrections, to appear in PR

Low-temperature ion beam mixing of Pt and Si markers in Ge

The mixing of Pt and Si marker atoms in Ge during 750-keV Xe irradiation was measured at temperatures between 6 and 500 K. The low-temperature measurements show that the mixing parameter for Pt is nearly twice that for Si. This result is in strong contradiction to the collisional theory of ion beam mixing. A weak temperature dependence in the mixing is found for both markers

Suppression of Phase Decoherence in a Single Atomic Qubit

We study the suppression of noise-induced phase decoherence in a single atomic qubit by employing pulse sequences. The atomic qubit is composed of a single neutral atom in a far-detuned optical dipole trap and the phase decoherence may originate from the laser intensity and beam pointing fluctuations as well as magnetic field fluctuations. We show that suitable pulse sequences may prolongate the qubit coherence time substantially as comparing to the conventional spin echo pulse.Comment: 4 pages, 3 figure

Fractionalized topological insulators from frustrated spin models in three dimensions

We present a theory of three dimensional fractionalized topological insulators in the form of U(1) spin liquids with gapped fermionic spinons in the bulk and topologically protected gapless spinon surface states. Starting from a spin-1/2 model on a pyrochlore lattice, with frustrated antiferromagnetic and ferromagnetic exchange interactions, we show that decomposition of the latter interactions, within slave-fermion representation of the spins, can naturally give rise to an emergent spin-orbit coupling for the spinons. This stabilizes a fractionalized topological insulators which also have bulk bond spin-nematic order. Finally, we describe the low energy properties of these states.Comment: 10 page