By Achintya Rao
Sasers developed!
Two groups of scientists have independently developed sound lasers, or sasers, that emit sound waves that are in phase with one another and can be focused in a given direction. The saser, which gets its name from Sound Amplification and Stimulated Emission of Radiation, has been developed by scientists at the University of Nottingham in the UK as well as at the California Institute of Technology (Caltech) in the US.
Both teams developed the sasers at different frequencies, indicating that they could be devised to work over a range of frequencies. In the same way that light has a wave and particle nature, sound can be thought of as having a particle nature represented by “phonons”. The research, published in Physical Review Letters, has been reported in physicsworld.com.
Van der Waals force may hold asteroids together
The Eros asteroid. Photo credit: NASA
Scientists studying the dusty surfaces of asteroids have suggested that the force holding them together might be the very same van der Waals force that is responsible for interactions between atoms and molecules. Daniel Scheeres and his colleagues from the University of Colorado in the US, and Michael Swift from the University of Nottingham in the UK compared all the forces that might hold an asteroid together. The findings were published in the online preprint archive, arXiv.org.
The suggestion, reported in physicsworld.com might sound surprising, but the two potential forces that may act on the particles – gravity and the van der Waals force – behave in different ways. Gravity is proportional to the mass of the particles, where as the van der Waals force changes according to the surface area. Based on their study, the researchers concluded that gravity was not effective in binding the rocks observed in smaller asteroids.
Physicists may have discovered a new phase of liquid hydrogen
Scientists conducting simulations of the molecular-to-atomic transition in liquid hydrogen have found evidence for a previously unknown liquid phase. Isaac Tamblyn from Dalhousie University in Halifax, Canada along with Stanimir A. Bonev also observed some intriguing structural characteristics of liquid hydrogen.
Tamblyn told PhysOrg.com about the simulation, and how it was conducted. They discovered the reasons behind certain characteristics of hydrogen, such as the fact that liquid hydrogen is denser than solid hydrogen. The research and the information obtained, presented in Physical Review Letters, suggest that physicists might have to revise equations of the properties of hydrogen as well as change the planetary models that we currently use.
One step closer to quantum computing
Physicists at the University of Wisconsin-Madison in the US have successfully created a circuit using two rubidium atoms, in an experiment that demonstrates the possibility of using atoms to build quantum computers.
Professors Mark Saffman and Thad Walker were able to take advantage of a seven-millionths-of-a-second window to build a controlled-NOT (C-NOT) gate, a circuit important for quantum computing. The significance of the experiment lies in the use of neutral atoms instead of charged ions that had been used previously. Since atoms do not normally interact with each other as ions do, more of them can be arranged together in a small region. Read the original report on PhysOrg.com.
Strange fluctuating magnetic waves detected in superconductors
The Meissner effect: a magnet levitating over a superconductor. Photo credit: Mai-Linh Doan
Researchers at Brown University in the US and others in France have studied for the first time what happens to electrons of a superconductor that are subjected to a magnetic field. Vesna Mitrovic and colleagues found that electrons in a superconducting material form strange, fluctuating magnetic waves under certain conditions.
It has been known for many years that there exists a relationship between magnetism and superconductivity (see image of Meissner effect), but the reason behind this relationship continued to baffle scientists. The research, mentioned in Science Daily, found that electrons in the superconducting material were tilted at various angles on their imaginary axes, and moved in a repeating pattern resembling waves. Most interestingly, the waves appeared to fluctuate under certain conditions. The scientists now hope to study why these fluctuations occur.
New material may revolutionise all-optical switching and computing
Scientists at Georgia Tech in the US have demonstrated a new class of material using molecules that could help develop all-optical switching devices. These devices would not require the signals to be converted from optical to electrical, then back again. These devices are essential for developing low-power, high-speed communications and computing.
Professors Seth Marder and Joseph Perry told PhysOrg.com about their work, which was reported in the 18 February edition of Science Express.
Cold-welding of gold and silver nanowires observed
Gold nanowires, seen under a Scanning Electron Microscope. Photo credit: Thomas Mårtensson/Kristian Mølhave
Scientists at Rice University in the US have observed cold welding at the nano-scale for the first time. Jun Lou and his team came across this phenomenon by accident, when they were studying the tensile strength of gold nanowires.
The results, reported in Nature Nanotechnology, show that gold and silver nanowires of a thickness between three-billionths and ten-billionths of a metre bond with one another without the application of heat and without a loss of their electrical or mechanical properties. The welded wires never broke at the same spot when the researchers tried to pull them apart, proving the strength of the bonds. Read the original article here.
Crystal tech could give us 3D displays
Researchers at the National University of Singapore have developed a method of controlling the growth of certain crystals that have useful optical properties. Xiaogang Liu and his colleagues used a process called doping where certain “impurities” are intentionally added to a substance for the favourable properties it lends. They successfully used elements from the lanthanide group to dope the crystal, allowing them to adjust the structure, size and light emission spectra of the crystals.
Because of its interesting optical properties, scientists believe that these crystals could be used to develop 3D displays. The discovery was published in Nature and was reported in physicsworld.com.