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Open access

2012-04-23

Open access

Nature Materials 11, 353 (2012). doi:10.1038/nmat3328

Open-access journals are publishing at a pace that is not much faster than some recently launched subscription-based journals. The swiftest and surest route to full open-access publishing is then for funders, institutions and publishers to agree on the conditions for self-archiving in publicly accessible repositories.

Nanoferronics is a winning combination

Manuel Bibes — 2012-04-23

Nanoferronics is a winning combination

Nature Materials 11, 354 (2012). doi:10.1038/nmat3318

Author: Manuel Bibes

Progress in controlling different ferroic orders such as ferromagnetism and ferroelectricity on the nanoscale could offer unprecedented possibilities for electronic applications.

Beaten to action

Joerg Heber — 2012-04-23

Beaten to action

Nature Materials 11, 358 (2012). doi:10.1038/nmat3325

Author: Joerg Heber

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Honey, I shrunk the mask

Christian Martin — 2012-04-23

Honey, I shrunk the mask

Nature Materials 11, 358 (2012). doi:10.1038/nmat3326

Author: Christian Martin

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Close to the edge

Fabio Pulizzi — 2012-04-23

Close to the edge

Nature Materials 11, 358 (2012). doi:10.1038/nmat3323

Author: Fabio Pulizzi

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Optimized for the clinic

Pep Pàmies — 2012-04-23

Optimized for the clinic

Nature Materials 11, 358 (2012). doi:10.1038/nmat3324

Author: Pep Pàmies

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Picking holes

Alison Stoddart — 2012-04-23

Picking holes

Nature Materials 11, 358 (2012). doi:10.1038/nmat3322

Author: Alison Stoddart

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Dendritic polymers: Universal glue for cells

Holger Frey — 2012-04-23

Dendritic polymers: Universal glue for cells

Nature Materials 11, 359 (2012). doi:10.1038/nmat3320

Author: Holger Frey

A dendritic polymer consisting of inversely oriented lipid head groups on a polyvalent polyglycerol scaffold makes an effective reversible biomembrane adhesive that may find use as a tissue sealant and a drug-delivery vehicle.

Ferromagnetic semicondutors: Battle of the bands

Nitin Samarth — 2012-04-23

Ferromagnetic semicondutors: Battle of the bands

Nature Materials 11, 360 (2012). doi:10.1038/nmat3317

Author: Nitin Samarth

Accurate and extensive measurements of the compositional dependence of the Curie temperature brings us one step closer to solving the puzzle of the origin of ferromagnetism in the model ferromagnetic semiconductor (Ga,Mn)As.

Material witness: Material computation

Philip Ball — 2012-04-23

Material witness: Material computation

Nature Materials 11, 362 (2012). doi:10.1038/nmat3321

Author: Philip Ball

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Supercooled liquids: Clearing the water

Austen Angell — 2012-04-23

Supercooled liquids: Clearing the water

Nature Materials 11, 362 (2012). doi:10.1038/nmat3319

Author: Austen Angell

Evidence of a transition between two coexisting liquids of the same composition in a water–glycerol mixture, where glycerol prevents the crystallization of water, provides a unique link to an elusive liquid–liquid transition in pure water.

Spintronics

Fabio Pulizzi — 2012-04-23

Spintronics

Nature Materials 11, 367 (2012). doi:10.1038/nmat3327

Author: Fabio Pulizzi

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New moves of the spintronics tango

Jairo Sinova — 2012-04-23

New moves of the spintronics tango

Nature Materials 11, 368 (2012). doi:10.1038/nmat3304

Authors: Jairo Sinova & Igor Žutić

The ability of spintronics to re-energize itself in directions that germinate new subfields has made it one of the most fertile grounds for basic research aimed at future applications. A brief overview of the connections between five emerging subfields suggests exciting things to come.

Current-induced torques in magnetic materials

Arne Brataas — 2012-04-23

Spin-transfer torque is the rotation that a spin-polarized current induces on the magnetization of the solid it flows through. The way in which currents generate torques in a wide variety of magnetic materials and structures is discussed in this Review, as well as recent state-of-the-art demonstrations of current-induced-torque devices that show great promise for enhancing the functionality of semiconductor devices.

Spin Hall effect devices

Tomas Jungwirth — 2012-04-23

The spin Hall effect is a relativistic spin–orbit coupling phenomenon, which can be used to electrically generate or detect spin currents in non-magnetic systems. This Review discusses the experiments that have established the basic physical understanding of the effect, and the role that several of the spin Hall devices have had in the demonstration of spintronic functionalities and physical phenomena.

Spin caloritronics

Gerrit E. W. Bauer — 2012-04-23

Spin caloritronics focuses on the interaction of electron spins with heat currents. This Review describes newly discovered physical effects that have re-invigorated the field by stimulating further research into understanding the fundamentals of spin–phonon interactions, and providing new avenues to explore to improve current thermoelectric technology.

Silicon spintronics

Ron Jansen — 2012-04-23

Control of the electron spin as well as its charge is predicted to lead to efficient electronic devices, with potentially new functionalities. Injecting and manipulating spin-polarized carriers in silicon is a natural step towards integrating spintronics with current technology. This Review describes the first encouraging results as well as the open questions and challenges that still remain.

Spintronics and pseudospintronics in graphene and topological insulators

Dmytro Pesin — 2012-04-23

Graphene and topological insulator two-dimensional electron systems are described by massless Dirac equations. Although the two systems have similar Hamiltonians, they are polar opposites in terms of spin–orbit coupling strength. The status of efforts to achieve long spin-relaxation times in weakly spin–orbit-coupled graphene, and large current-induced spin-polarizations in strongly spin–orbit-coupled topological insulator surface states are reviewed in this Progress Article.

Josephson supercurrent through a topological insulator surface state

M. Veldhorst — 2012-02-19

Josephson supercurrent through a topological insulator surface state

Nature Materials 11, 417 (2012). doi:10.1038/nmat3255

Authors: M. Veldhorst, M. Snelder, M. Hoek, T. Gang, V. K. Guduru, X. L. Wang, U. Zeitler, W. G. van der Wiel, A. A. Golubov, H. Hilgenkamp & A. Brinkman

The long-sought yet elusive Majorana fermion is predicted to arise from a combination of a superconductor and a topological insulator. An essential step in the hunt for this emergent particle is the unequivocal observation of supercurrent in a topological phase. Here, direct evidence for Josephson supercurrents in superconductor (Nb)–topological insulator (Bi2Te3)–superconductor electron-beam fabricated junctions is provided by the observation of clear Shapiro steps under microwave irradiation, and a Fraunhofer-type dependence of the critical current on magnetic field. Shubnikov–de Haas oscillations in magnetic fields up to 30 T reveal a topologically non-trivial two-dimensional surface state. This surface state is attributed to mediate the ballistic Josephson current despite the fact that the normal state transport is dominated by diffusive bulk conductivity. The lateral Nb–Bi2Te3–Nb junctions hence provide prospects for the realization of devices supporting Majorana fermions.

Copper ion liquid-like thermoelectrics

Huili Liu — 2012-03-11

Copper ion liquid-like thermoelectrics

Nature Materials 11, 422 (2012). doi:10.1038/nmat3273

Authors: Huili Liu, Xun Shi, Fangfang Xu, Linlin Zhang, Wenqing Zhang, Lidong Chen, Qiang Li, Ctirad Uher, Tristan Day & G. Jeffrey Snyder

Advanced thermoelectric technology offers a potential for converting waste industrial heat into useful electricity, and an emission-free method for solid state cooling. Worldwide efforts to find materials with thermoelectric figure of merit, zT values significantly above unity, are frequently focused on crystalline semiconductors with low thermal conductivity. Here we report on Cu2−xSe, which reaches a zT of 1.5 at 1,000 K, among the highest values for any bulk materials. Whereas the Se atoms in Cu2−xSe form a rigid face-centred cubic lattice, providing a crystalline pathway for semiconducting electrons (or more precisely holes), the copper ions are highly disordered around the Se sublattice and are superionic with liquid-like mobility. This extraordinary ‘liquid-like’ behaviour of copper ions around a crystalline sublattice of Se in Cu2−xSe results in an intrinsically very low lattice thermal conductivity which enables high zT in this otherwise simple semiconductor. This unusual combination of properties leads to an ideal thermoelectric material. The results indicate a new strategy and direction for high-efficiency thermoelectric materials by exploring systems where there exists a crystalline sublattice for electronic conduction surrounded by liquid-like ions.

Gradient-index meta-surfaces as a bridge linking propagating waves and surface waves

Shulin Sun — 2012-04-01

Gradient-index meta-surfaces as a bridge linking propagating waves and surface waves

Nature Materials 11, 426 (2012). doi:10.1038/nmat3292

Authors: Shulin Sun, Qiong He, Shiyi Xiao, Qin Xu, Xin Li & Lei Zhou

The arbitrary control of electromagnetic waves is a key aim of photonic research. Although, for example, the control of freely propagating waves (PWs; refs , , , , , ) and surface waves (SWs; refs , , , ) has separately become possible using transformation optics and metamaterials, a bridge linking both propagation types has not yet been found. Such a device has particular relevance given the many schemes of controlling electromagnetic waves at surfaces and interfaces, leading to trapped rainbows, lensing, beam bending, deflection, and even anomalous reflection/refraction. Here, we demonstrate theoretically and experimentally that a specific gradient-index meta-surface can convert a PW to a SW with nearly 100% efficiency. Distinct from conventional devices such as prism or grating couplers, the momentum mismatch between PW and SW is compensated by the reflection-phase gradient of the meta-surface, and a nearly perfect PW–SW conversion can happen for any incidence angle larger than a critical value. Experiments in the microwave region, including both far-field and near-field characterizations, are in excellent agreement with full-wave simulations. Our findings may pave the way for many applications, including high-efficiency surface plasmon couplers, anti-reflection surfaces, light absorbers, and so on.

A super-oscillatory lens optical microscope for subwavelength imaging

Edward T. F. Rogers — 2012-03-25

A super-oscillatory lens optical microscope for subwavelength imaging

Nature Materials 11, 432 (2012). doi:10.1038/nmat3280

Authors: Edward T. F. Rogers, Jari Lindberg, Tapashree Roy, Salvatore Savo, John E. Chad, Mark R. Dennis & Nikolay I. Zheludev

The past decade has seen an intensive effort to achieve optical imaging resolution beyond the diffraction limit. Apart from the Pendry–Veselago negative index superlens, implementation of which in optics faces challenges of losses and as yet unattainable fabrication finesse, other super-resolution approaches necessitate the lens either to be in the near proximity of the object or manufactured on it, or work only for a narrow class of samples, such as intensely luminescent or sparse objects. Here we report a new super-resolution microscope for optical imaging that beats the diffraction limit of conventional instruments and the recently demonstrated near-field optical superlens and hyperlens. This non-invasive subwavelength imaging paradigm uses a binary amplitude mask for direct focusing of laser light into a subwavelength spot in the post-evanescent field by precisely tailoring the interference of a large number of beams diffracted from a nanostructured mask. The new technology, which—in principle—has no physical limits on resolution, could be universally used for imaging at any wavelength and does not depend on the luminescence of the object, which can be tens of micrometres away from the mask. It has been implemented as a straightforward modification of a conventional microscope showing resolution better than λ/6.

Liquid–liquid transition without macroscopic phase separation in a water–glycerol mixture

Ken-ichiro Murata — 2012-03-18

The plausible existence of a liquid–liquid transition (LLT) pre-empted by crystallization in supercooled water has long been debated. So far, indications of such a ‘hidden’ LLT have been found in nanoconfined water and in the amorphous polymorphism of ice. Now, the finding of an isocompositional LLT in a water–glycerol mixture where glycerol prevents water crystallization suggests a new link to an elusive LLT in pure water.

Controlling the Curie temperature in (Ga,Mn)As through location of the Fermi level within the impurity band

M. Dobrowolska — 2012-02-19

Controlling the Curie temperature in (Ga,Mn)As through location of the Fermi level within the impurity band

Nature Materials 11, 444 (2012). doi:10.1038/nmat3250

Authors: M. Dobrowolska, K. Tivakornsasithorn, X. Liu, J. K. Furdyna, M. Berciu, K. M. Yu & W. Walukiewicz

Infrared metamaterial phase holograms

Stéphane Larouche — 2012-03-18

Infrared metamaterial phase holograms

Nature Materials 11, 450 (2012). doi:10.1038/nmat3278

Authors: Stéphane Larouche, Yu-Ju Tsai, Talmage Tyler, Nan M. Jokerst & David R. Smith

Sparsity-based single-shot subwavelength coherent diffractive imaging

A. Szameit — 2012-04-01

Sparsity-based single-shot subwavelength coherent diffractive imaging

Nature Materials 11, 455 (2012). doi:10.1038/nmat3289

Authors: A. Szameit, Y. Shechtman, E. Osherovich, E. Bullkich, P. Sidorenko, H. Dana, S. Steiner, E. B. Kley, S. Gazit, T. Cohen-Hyams, S. Shoham, M. Zibulevsky, I. Yavneh, Y. C. Eldar, O. Cohen & M. Segev

A silica sol–gel design strategy for nanostructured metallic materials

Scott C. Warren — 2012-03-18

A silica sol–gel design strategy for nanostructured metallic materials

Nature Materials 11, 460 (2012). doi:10.1038/nmat3274

Authors: Scott C. Warren, Matthew R. Perkins, Ashley M. Adams, Marleen Kamperman, Andrew A. Burns, Hitesh Arora, Erik Herz, Teeraporn Suteewong, Hiroaki Sai, Zihui Li, Jörg Werner, Juho Song, Ulrike Werner-Zwanziger, Josef W. Zwanziger, Michael Grätzel, Francis J. DiSalvo & Ulrich Wiesner

Polyvalent choline phosphate as a universal biomembrane adhesive

Xifei Yu — 2012-03-18

Polyvalent choline phosphate as a universal biomembrane adhesive

Nature Materials 11, 468 (2012). doi:10.1038/nmat3272

Authors: Xifei Yu, Zonghua Liu, Johan Janzen, Irina Chafeeva, Sonja Horte, Wei Chen, Rajesh K. Kainthan, Jayachandran N. Kizhakkedathu & Donald E. Brooks