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This Letter reports measurements of the magnetic field dependence of the resistive critical temperature T c of a regular square network of superconducting aluminum. We find new effects of flux quantization corresonding to both integral (1,2,3,...) and fractional (T>T>T>T>T>T>T) numbers of flux quanta per unit cell of the network. The fractal fine structure of the upper critical-field line is identified as the edge of the Landau-level spectrum for a tight-binding problem on a square lattice.

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We have performed thermal conductance measurements on individual single crystalline silicon suspended nanowires. The nanowires (130 nm thick and 200 nm wide) are fabricated by e-beam lithography and suspended between two separated pads on Silicon On Insulator (SOI) substrate. We measure the thermal conductance of the phonon wave guide by the 3ω method. The cross-section of the nanowire approaches the dominant phonon wave length in silicon which is of the order of 100 nm at 1K. Above 1.3K the conductance behaves as T 3 , but a deviation is measured at the lowest temperature which can be attributed to the reduced geometry.