16,674 research outputs found
Translation invariant topological superconductors on lattice
In this paper we introduce four Z_2 topological indices zeta_k=0,1 at
k=(0,0), (0,pi), (pi, 0), (pi, pi) characterizing 16 universal classes of 2D
superconducting states that have translation symmetry but may break any other
symmetries. The 16 classes of superconducting states are distinguished by their
even/odd numbers of fermions on even-by-even, even-by-odd, odd-by-even, and
odd-by-odd lattices. As a result, the 16 classes topological superconducting
states exist even for interacting systems. For non-interacting systems, we find
that zeta_k is the number of electrons on k=(0,0), (0,pi), (pi, 0), or (pi,pi)
orbitals (mod 2) in the ground state. For 3D superconducting states with only
translation symmetry, there are 256 different types of topological
superconductors.Comment: 4 pages, RevTeX
Quantum Field Theory Description of Tunneling in the Integer Quantum Hall Effect
We study the tunneling between two quantum Hall systems, along a quasi
one-dimensional interface. A detailed analysis relates microscopic parameters,
characterizing the potential barrier, with the effective field theory model for
the tunneling. It is shown that the phenomenon of fermion number
fractionalization is expected to occur, either localized in conveniently
modulated barriers or in the form of free excitations, once lattice effects are
taken into account. This opens the experimental possibility of an observation
of fractional charges with internal structure, close to the magnetic length
scale. The coupling of the system to external gauge fields is performed,
leading us to the exact quantization of the Hall conductivity at the interface.
The field theory approach is well supported by a numerical diagonalization of
the microscopic Hamiltonian.Comment: 34 pages, PUPT-1468. (3 figures available upon resquest to the
authors at [email protected] or [email protected]
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An effective frame breaking policy for dynamic framed slotted aloha in RFID
The tag collision problem is considered as one of the critical issues in RFID system. To further improve the identification efficiency of an UHF RFID system, a frame breaking policy is proposed with dynamic framed slotted aloha algorithm. Specifically, the reader makes effective use of idle, successful, and collision statistics during the early observation phase to recursively determine the optimal frame size. Then the collided tags in each slot will be resolved by individual frames. Simulation results show that the proposed algorithm achieves a better identification performance compared with the existing Aloha-based algorithms
Macroscopic Quantum Tunneling Effect of Z2 Topological Order
In this paper, macroscopic quantum tunneling (MQT) effect of Z2 topological
order in the Wen-Plaquette model is studied. This kind of MQT is characterized
by quantum tunneling processes of different virtual quasi-particles moving
around a torus. By a high-order degenerate perturbation approach, the effective
pseudo-spin models of the degenerate ground states are obtained. From these
models, we get the energy splitting of the ground states, of which the results
are consistent with those from exact diagonalization methodComment: 25 pages, 14 figures, 4 table
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