A DNA nanostructure consisting of four four-arm junctions oriented with a square aspect ratio was designed and constructed. Programmable self-assembly of 4 x 4 tiles resulted in two distinct lattice morphologies: uniform-width nanoribbons and two-dimensional nanogrids, which both display periodic square cavities. Periodic protein arrays were achieved by templated self-assembly of streptavidin onto the DNA nanogrids containing biotinylated oligonucleotides. On the basis of a two-step metallization procedure, the 4 x 4 nanoribbons acted as an excellent scaffold for the production of highly conductive, uniform-width, silver nanowires.

We report on optical measurements of a two-dimensiona1 electron gas near the metal-insulator transition. We observe the appearance of excitons and negatively charged excitons, X, at the onset of the transition. The fact that these excitons appear at a relatively large average electron density shows that transition is induced by localization of single electrons in the electrostatic potential fluctuations of the remote ionized donors. PACS numbers: 71.30.+h, 71.35.+z, 73.20.Dx, 78.66.Fd Modulation-doped semiconductor quantum well is a heterostructure in which a layer of donors is introduced within the barrier region. The spatial separation between these donors and the two-dimensional electron gas

A novel promising route for creating topological states and excitations is to combine superconductivity and the quantum Hall (QH) effect [1,2] . Despite this potential, signatures of superconductivity in the quantum Hall regime remain scarce [5][6][7][8][9][10][11] , and a superconducting current through a QH weak link has so far eluded experimental observation. Here we demonstrate the existence of a new type of supercurrent-carrying states in a QH region at magnetic fields as high as 2 Tesla. The observation of supercurrent in the quantum Hall regime marks an important step in the quest for exotic topological excitations such as Majorana fermions and parafermions, which may find applications in fault-tolerant quantum computations.1 arXiv:1512.09083v1 [cond-mat.mes-hall] Dec 2015The interplay of the quantum Hall effect with superconductivity is expected to result in novel excitations with non-trivial braiding statistics such as Majorana fermions and non-abelian Majorana anyons [1][2][3][4] . When a quantum Hall region is contacted by two superconducting electrodes, the gapped QH bulk prevents the flow of a supercurrent. However, it was predicted more than 20 years ago that the supercurrent may still be mediated by QH edge states [12] . Due to its chiral nature, a single edge can only conduct charge carriers in one direction, so both edges have to be involved in establishing supercurrent between the two contacts. This situation is fundamentally different from the Josephson junctions made of two-dimensional topological insulators, where each edge can support its own supercurrent [13][14][15][16] . Indeed, contrary to the case of topological insulators, the magnetic field in the QH regime breaks time-reversal symmetry, which is essential for the s-wave pairing of conventional superconductors. Nonetheless, we observe a robust supercurrent in the quantum Hall regime, which we attribute to an unconventional form of Andreev bound states circulating along the perimeter of the QH region and involving electron and hole trajectories separated by several micrometers. We performed transport measurements on four Josephson junctions (J 1−4 ) made of graphene encapsulated in boron nitride and contacted by electrodes made of a molybdenum-rhenium alloy [Fig. 1a] [11] , a type II superconductor with a high upper critical field of H c2 =8 T. The high quality of these heterostructures allowed us to observe Fabry-Perot oscillations of the junctions' resistance and critical current, indicating that the transmission of charge carriers between the contacts is ballistic [17] . The supercurrent is uniformly distributed along the width of the contacts, as evidenced by the regular Fraunhofer pattern [18] measured at small magnetic fields [17] . All junctions demonstrate supercurrent in the QH regime; for consistency, we choose to present data measured on sample J 1 , which has a distance between contacts L = 0.3 µm and a width of the contacts W = 2.4µm (see Figure 1b). Recent preprint reported on the observation of supercurrent ...

We present a DNA nanostructure, the three-helix bundle (3HB), which consists of three double helical DNA domains connected by six immobile crossover junctions such that the helix axes are not coplanar. The 3HB motif presents a triangular cross-section with one helix lying in the groove formed by the other two. By differential programming of sticky-ends, 3HB tiles can be arrayed in two distinct lattice conformations: one-dimensional filaments and two-dimensional lattices. Filaments and lattices have been visualized by high-resolution, tapping mode atomic force microscopy (AFM) under buffer. Their dimensions are shown to be in excellent agreement with designed structures. We also demonstrate an electroless chemical deposition for fabricating metallic nanowires templated on self-assembled filaments. The metallized nanowires have diameters down to 20 nm and display Ohmic current-voltage characteristic.