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The research shows that a spin liquid state exists in Herbertsmithite—a mineral whose atoms form a kagome lattice, named for a simple weaving pattern of repeating triangles well-known in Japan. Kagome lattices are one of the simplest structures believed to possess a spin liquid state, and the new findings, revealed by neutron scattering, indeed show striking evidence for a fundamental prediction of spin liquid physics.


This image depicts magnetic effects within Herbertsmithite crystals, where green regions represent higher scattering of neutrons from NIST's Multi-Angle Crystal Spectrometer (MACS). Scans of typical highly-ordered magnetic materials show only isolated spots of green, while disordered materials show uniform color over the entire sample. The in-between nature of this data shows some order within the disorder, implying the unusual magnetic effects within a spin liquid.
Credit: NIST


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A carbon-nanotube-coated lens that converts light to sound can focus high-pressure sound waves to finer points than ever before. Researchers say it could lead to an invisible knife for noninvasive surgery.

Today focused sound waves blast apart kidney stones and prostate tumors. The tools work primarily by focusing sound waves tightly enough to generate heat.

"A major drawback of current strongly focused ultrasound technology is a bulky focal spot, which is on the order of several millimeters," Baac said. "A few centimeters is typical. Therefore, it can be difficult to treat tissue objects in a high-precision manner, for targeting delicate vasculature, thin tissue layer and cellular texture. We can enhance the focal accuracy 100-fold."

The team was able to concentrate high-amplitude sound waves to a speck just 75 by 400 micrometers (a micrometer is one-thousandth of a millimeter). Their beam can blast and cut with pressure, rather than heat.


With a new technique that uses tightly-focussed sound waves for micro-surgery, University of Michigan engineering researchers drilled a 150-micrometer hole in a confetti-sized artificial kidney stone. Image credit: Hyoung Won Baac


Nature Scientific Reports - Carbon-Nanotube Optoacoustic Lens for Focused Ultrasound Generation and High-Precision Targeted Therapy

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Scanning tunneling microscopy (STM) is routinely employed by physicists and chemists to capture atomic-scale images of molecules on surfaces. Now, an international team led by Christian Joachim and co-workers from the A*STAR Institute of Materials Research and Engineering has taken STM a step further: using it to identify the quantum states within ‘super benzene’ compounds using STM conductance measurements1. Their results provide a roadmap for developing new types of quantum computers based on information localized inside molecular bonds.

To gain access to the quantum states of hexabenzocoronene (HBC) — a flat aromatic molecule made of interlocked benzene rings — the researchers deposited it onto a gold substrate. According to team member We-Hyo Soe, the weak electronic interaction between HBC and gold is crucial to measuring the system’s ‘differential conductance’ — an instantaneous rate of current charge with voltage that can be directly linked to electron densities within certain quantum states.

After cooling to near-absolute zero temperatures, the team maneuvered its STM tip to a fixed location above the HBC target. Then, they scanned for differential conductance resonance signals at particular voltages. After detecting these voltages, they mapped out the electron density around the entire HBC framework using STM. This technique provided real-space pictures of the compound’s molecular orbitals — quantized states that control chemical bonding.


High-resolution microscopy reveals that a benzene-like molecule known as HBC has a quantized electron density around its ring framework (left). Theoretical calculations show that the observed quantum states change with different tip positions (right, upper/lower images, respectively).

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The field of metamaterials involves augmenting materials with specially designed patterns, enabling those materials to manipulate electromagnetic waves and fields in previously impossible ways. Now, researchers from the University of Pennsylvania have come up with a theory for moving this phenomenon onto the quantum scale, laying out blueprints for materials where electrons have nearly zero effective mass.

Their idea was born out of the similarities and analogies between the mathematics that govern electromagnetic waves — Maxwell’s Equations — and those that govern the quantum mechanics of electrons — Schrödinger’s Equations.

On the electromagnetic side, inspiration came from work the two researchers had done on metamaterials that manipulate permittivity, a trait of materials related to their reaction to electric fields. They theorized that, by alternating between thin layers of materials with positive and negative permittivity, they could construct a bulk metamaterial with an effective permittivity at or near zero. Critically, this property is only achieved when an electromagnetic wave passes through the layers head on, against the grain of the stack. This directional dependence, known as anisotropy, has practical applications.

The researchers saw parallels between this phenomenon and the electron transport behavior demonstrated in Leo Esaki’s Nobel Prize-winning work on superlattices in the 1970s: semiconductors constructed out of alternating layers of materials, much like the permittivity-altering metamaterial.

Physical Review B - Transformation electronics: Tailoring the effective mass of electrons

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By the end of 2013, nearly 400,000 plug-in electric vehicles (PEVs) will be dri the worldwide market for e-bicycles will increase at a compound annual growth rate (CAGR) of 7.5% between 2012 and 2018, resulting in global sales of more than 47 million vehicles in 2018. China is anticipated to account for 42 million of these e-bicycles that year, giving it 89% of the total world market. The e-bicycle market is anticipated to generate $6.9 billion in worldwide revenue in 2012, growing to $11.9 billion in 2018.ving on roads around the world.

Sales of electric bicycles in North America will grow by more than 50% in 2013 to more than 158,000 bikes. The world electric bicycle market will grow by 10% to more than 33.6 million units during that year. Almost of the global electric bikes will be in China.

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Arxiv - Experimental signature of programmable quantum annealing (12 pages) This work shows that Dwave Systems adiabatic quantum computing system is leveraging quantum effects for up to 20 milliseconds. Different experiments are needed to calculate the speedup relative to optimal classical systems.

Quantum annealing is a general strategy for solving difficult optimization problems with the aid of quantum adiabatic evolution. Both analytical and numerical evidence suggests that under idealized, closed system conditions, quantum annealing can outperform classical thermalization-based algorithms such as simulated annealing. Do engineered quantum annealing devices effectively perform classical thermalization when coupled to a decohering thermal environment? To address this we establish, using superconducting flux qubits with programmable spin-spin couplings, an experimental signature which is consistent with quantum annealing, and at the same time inconsistent with classical thermalization, in spite of a decoherence timescale which is orders of magnitude shorter than the adiabatic evolution time. This suggests that programmable quantum devices, scalable with current superconducting technology, implement quantum annealing with a surprising robustness against noise and imperfections.

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