Monday, January 25, 2010

^{75} As NMR study of single crystals of the heavily overdoped pnictide superconductors Ba_{1−x} K_{x} Fe_{2} As_{2} ( x=0.7 and 1)

from Recent Articles in Phys. Rev. B We performed 75As NMR studies on two overdoped high-quality Ba1−xKxFe2As2 (x=0.7 and 1.0) single crystals. In the normal states, we found a dramatic increase in the spin-lattice relaxation (1/75T1) from the x=0.7 to the x=1.0 samples. In KFe2As2, the ratio of 1/75T1TKn2, where 75Kn is the Knight shift, increases as temperature drops. These results indicate the existence of another type of spin fluctuations in KFe2As2 which is accustomed to being treated as a simple Fermi liquid. In the superconducting state, the temperature scalings of 1/75T1 below Tc in the overdoped samples are significantly different from those in the under or optimally doped ones. A power-law scaling behavior 1/75T1TT0.5 is observed, which indicates universal strong low-energy excitations in the overdoped hole-type superconductors.

Quantum interface between light and nuclear spins in quantum dots

from Recent Articles in Phys. Rev. B The coherent coupling of flying photonic qubits to stationary matter-based qubits is an essential building block for quantum-communication networks. We show how such a quantum interface can be realized between a traveling-wave optical field and the polarized nuclear spins in a singly charged quantum dot strongly coupled to a high-finesse optical cavity. By adiabatically eliminating the electron a direct effective coupling is achieved. Depending on the laser field applied, interactions that enable either write-in or read-out are obtained.

nhomogeneous nuclear spin flips: Feedback mechanism between electronic states in a double quantum dot and the underlying nuclear spin bath

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