Physical properties of noncentrosymmetric superconductor Ru7_7B3_3

Transition metal boride Ru$_7$B$_3$ was found to be a noncentrosymmetric superconductor with $T_{C}$ equal to 3.3 K. Superconducting and normal state properties of Ru$_7$B$_3$ were determined by a self-consistent analysis through resistivity($\rho_{xx}$ and $\rho_{xy}$), specific heat, lower critical field measurement and electronic band structure calculation. It is found that Ru$_7$B$_3$ belongs to an s-wave dominated single band superconductor with energy gap 0.5 meV and could be categorized into type II superconductor with weak electron-phonon coupling. Unusual 'kink' feature is clearly observed in field-broadening resistivity curves, suggesting the possible mixture of spin triplet induced by the lattice without inversion symmetry.Comment: 11 pages, 16 figures. submitted to Phys. Rev.

Bis(dimethyl­ammonium) 2,2′-(1,3,6,8-tetra­oxo-2,7-diaza­pyrene-2,7-di­yl)diacetate

The asymmetric unit of title compound, 2C2H8N+·C18H8N2O8 2−, comprises one crystallographically independent dimethyl­ammonium cation and half of a 2,2′-(1,3,6,8-tetra­oxo-2,7-diaza­pyrene-2,7-di­yl)diacetate dianion. The anion lies on an inversion centre and the two carboxyl­ate groups are in trans positions based on the naphthaleneteracarb­oxy­lic diimide group. The crystal packing is stabilized by N—H⋯O hydrogen bonds between cations and anions, as well as by π–π inter­actions between the naph­thaleneteracarb­oxy­lic diimide groups [centroid–centroid distance = 4.812 (3) Å]

Coexistence of directed momentum current and ballistic energy diffusion in coupled non-Hermitian kicked rotors

We numerically investigate the quantum transport in a coupled kicked rotors with the $\mathcal{PT}$-symmetric potential. We find that the spontaneous $\mathcal{PT}$-symmetry breaking of wavefunctions emerges when the amplitude of the imaginary part of the complex potential is beyond a threshold value, which can be modulated by the coupling strength effectively. In the regime of the $\mathcal{PT}$-symmetry breaking, the particles driven by the periodical kicks move unidirectionally in momentum space, indicating the emergence of a directed current. Meanwhile, with increasing the coupling strength, we find a transition from the ballistic energy diffusion to a kind of the modified ballistic energy diffusion where the width of the wavepacket also increases with time in a power law. Our findings suggest that the decoherence effect induced by the interplay between the inter-particle coupling and the non-Hermitian driving potential is responsible for these particular transport behaviors.Comment: 8 pages, 7 figure