Achieving complete absorption of visible light with a minimal amount of material is highly desirable for many applications, including solar energy conversion to fuel and electricity, where benefits in conversion efficiency and economy can be obtained. On a fundamental level, it is of great interest to explore whether the ultimate limits in light absorption per unit volume can be achieved by capitalizing on the advances in metamaterial science and nanosynthesis. Here, we combine block copolymer lithography and atomic layer deposition to tune the effective optical properties of a plasmonic array at the atomic scale. Critical coupling to the resulting nanocomposite layer is accomplished through guidance by a simple analytical model and measurements by spectroscopic ellipsometry. Thereby, a maximized absorption of light exceeding 99% is accomplished, of which up to about 93% occurs in a volume-equivalent thickness of gold of only 1.6 nm. This corresponds to a record effective absorption coefficient of 1.7 × 10(7) cm(-1) in the visible region, far exceeding those of solid metals, graphene, dye monolayers, and thin film solar cell materials. It is more than a factor of 2 higher than that previously obtained using a critically coupled dye J-aggregate, with a peak width exceeding the latter by 1 order of magnitude. These results thereby substantially push the limits for light harvesting in ultrathin, nanoengineered systems.

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We describe a magnetic recording media composed of antiferromagnetically coupled (AFC) magnetic recording layers as an approach to extend areal densities of longitudinal media beyond the predicted superparamagnetic limit. The recording medium is made up of two ferromagnetic layers separated by a nonmagnetic layer whose thickness is tuned to couple the layers antiferromagnetically. For such a structure, the effective areal moment density (Mrt) of the composite structure is the difference between the ferromagnetic layers allowing the effective magnetic thickness to scale independently of the physical thickness of the media. Experimental realizations of AFC media demonstrate that thermally stable, low-Mrt media suitable for high-density recording can be achieved.

International audienceElectron-beam ͑E-beam͒ directed assembly, which combines the long-range phase and placement registration of e-beam lithography with the sharp dot size and spacing uniformity of block copolymer self assembly, is considered highly promising for fabricating templates that meet the tight magnetic specifications required for write synchronization in bit patterned media magnetic recording systems. In our study, we show that this approach also yields a narrower magnetic switching field distribution ͑SFD͒ than e-beam patterning or block copolymer self-assembly alone. We demonstrate that the pattern uniformity, i.e., island diameter and placement distributions are also important for achieving tight magnetic SFDs. Bit patterned media ͑BPM͒ magnetic recording systems at densities in excess of 1 Tb/ in 2 require an extremely tight lithographic bit placement accuracy and a narrow size distribution of less than 5% in order to achieve good write synchronization between the recording head and the patterned media. 1 Nanoimprint technology with master molds fabricated via e-beam directed assembly of block copolymer films is considered a very promising cost-effective approach for creating highly uniform magnetic dot patterns over large areas. 2,3 In addition to the tight lithographic specifications for BPM, a narrow switching field distribution ͑SFD͒ of the magnetic dots is critical to ensure exact bit addressability without overwriting adjacent bits

Quantum phase is not a direct observable and is usually determined by interferometric methods. We present a method to map complete electron wave functions, including internal quantum phase information, from measured single-state probability densities. We harness the mathematical discovery of drum-like manifolds bearing different shapes but identical resonances, and construct quantum isospectral nanostructures possessing matching electronic structure but divergent physical structure. Quantum measurement (scanning tunneling microscopy) of these "quantum drums" [degenerate two-dimensional electron states on the Cu(111) surface confined by individually positioned CO molecules] reveals that isospectrality provides an extra topological degree of freedom enabling robust quantum state transplantation and phase extraction.Comment: Published 8 February 2008 in Science; 13 page manuscript (including 4 figures) + 13 page supplement (including 6 figures); supplementary movies available at http://mota.stanford.ed