A new topological insulator breaks symmetry, and that's a good thing

A new topological insulator breaks symmetry, and that's a good thing: Most topological insulators operate as either a p-type or n-type material on both top and bottom surfaces. But BiTeCl is asymmetric: p-type on its top surface and n-type on its bottom. This means the edges of the material could function as p-n junctions – or even many microscopic p-n junctions layered on top of each other. Even better, when the material is placed in a magnetic field, these p-n junctions develop unique edge channels that can conduct electricity with zero resistance, Chen said – and this opens all sorts of possibilities.

Moreover, this unique type of material can demonstrate many other phenomena. For instance, placing it in a static electric field can induce useful magnetic properties in the material, a phenomenon known as the topological magneto-electric effect, first predicted by theorist Shoucheng Zhang of the Stanford Institute for Materials and Energy Sciences and his group. You could even use an electric charge to induce magnetic monopoles – theorized magnets that have just one pole, north or south, rather than the usual two – and then use this exotic magnetic state to do practical work, such as storing information on a hard drive, Chen said. "This is very bizarre," he said, "because people have never found magnetic monopoles as fundamental particles."

Physicists Net Fractal Butterfly: Scientific American

Physicists Net Fractal Butterfly: Scientific American: ...the pattern describes the behavior of electrons in extreme magnetic fields...

...It was known at the time that electrons under the influence of a magnetic field would race around in circles. But Hofstadter found that in theory, if the electrons were confined inside a crystalline atomic lattice, their motion would become complicated. As the magnetic field was cranked up, the energy levels that define the motion of electrons would split again and again. When represented on a graph, those energy levels revealed a pattern that looked like a butterfly — and continued to do so, even when zoomed in to infinitely small scales...

 In May, researchers reported that they had stacked a single sheet of graphene, in which carbon atoms are arranged like a honeycomb, on top of a sheet of honeycombed boron nitride. The layers create a repeating pattern that provides a larger target for magnetic fields than the hexagons in each material — effectively magnifying the field.

Topology: The Secret Ingredient In The Latest Theory of Everything

Topology: The Secret Ingredient In The Latest Theory of Everything: Today, Wen combines topology, symmetry and quantum mechanics in a new theory that predicts the existence of new states of matter, unifies various puzzling phenomena in solid state physics and allows the creation artificial vacuums populated with artificial photons and electrons...

Xiao-Gang Wen's approach is to explore the properties of matter when the topological links between particles become much more general and complex. He generalises these links, thinking of them as strings that can connect many  particles together. In fact, he considers the way many strings can form net-like structures that have their own emergent properties...
That makes string nets a kind of "quantum ether" through which electromagnetic waves travel. That's a big claim.

Physicists induce high-temperature superconductivity in semiconductor with Scotch tape

Physicists induce high-temperature superconductivity in semiconductor with Scotch tape: "Typically, junctions between semi-conductors and superconductors were made by complex material growth procedures and fabricating devices with features smaller than a human hair," explains Burch. "However the cuprates have a completely different structure and complex chemical make-up that simply can't be incorporated with a normal semiconductor."

So instead, the team used Scotch poster tape and glass slides to place high-temperature superconductors in proximity with a special type of semi-conductor known as a topological insulator.

Materials scientists develop topological insulator with a switch

Materials scientists develop topological insulator with a switch: ...Cui’s group formed the compound into six-sided nanoplates whose properties could be controlled by switching a separate electrical current on and off; that’s the gating part. Flipping the switch one way caused the compound to behave as an n-type material – one in which electricity is conducted by negatively-charged electrons. Flipping the switch the other way turned the compound into a p-type material, in which positively charged “holes” carried the current...

Lasers could produce much sought-after band gaps in graphene

Lasers could produce much sought-after band gaps in graphene: In a new study, Foa Torres and his coauthors have addressed this problem. By analyzing the way that a laser field interacts with electrons in graphene, the researchers have predicted that shining a mid-infrared laser on graphene can produce band gaps in its electronic structure. Further, the researchers predict that the band gaps could be tuned by controlling the laser polarization. As Foa Torres explained, the key to how polarized light "opens up" band gaps in graphene involves electrons interacting with the laser field.
“Imagine an electron moving, say from left to right, into a region illuminated by the laser field,” he said. “Then what happens is that the electron interacts with the radiation by absorbing or emitting photons. This interaction leads to the electron being reflected or backscattered, as it would have hit a wall: the band gap. In contrast with usual band gaps, this one is dynamically produced by the laser.”

Physicists demonstrate coveted 'spin-orbit coupling' in atomic gases

Physicists demonstrate coveted 'spin-orbit coupling' in atomic gases: One of the most important phenomena in quantum physics, spin-orbit coupling describes the interplay that can occur between a particle's internal properties and its external properties. In atoms, it usually describes interactions that only occur within an atom: how an electron's orbit around an atom's core (nucleus) affects the orientation of the electron's internal bar-magnet-like "spin." In semiconductor materials such as gallium arsenide, spin-orbit coupling is an interaction between an electron's spin and its linear motion in a material...

In their experiment, researchers trapped and cooled a gas of about 200,000 rubidium-87 atoms down to 100 nanokelvins, 3 billion times colder than room temperature. The researchers selected a pair of energy states, analogous to the "spin-up" and "spin-down" states in an electron, from the available atomic energy levels. An atom could occupy either of these "pseudospin" states. Then researchers shined a pair of lasers on the atoms so as to change the relationship between the atom's energy and its momentum (its mass times velocity), and therefore its motion. This created spin-orbit coupling in the atom: the moving atom flipped between its two "spin" states at a rate that depended upon its velocity.
"This demonstrates that the idea of using laser light to create spin-orbit coupling in atoms works.

First observation of particles that are their own antiparticles could be on its way

First observation of particles that are their own antiparticles could be on its way: The device proposed by Onoda and his colleagues offers deliberate control over Majorana particles within a topological insulator that they hope will make them accessible to experiments. Their device consists of a surface of a superconducting topological insulator attached to two magnetic sections. The magnetic fields of the two magnets point in opposite directions. The researchers predict that, along the interface between the magnets, a periodic chain of magnetic field lines form in the superconducting topological insulator. Each of these magnetic field lines could accommodate a Majorana particle.
Once their existence is proved, Majorana particles could also enable extremely stable new forms of computing based on quantum physics, says Onoda.

Topologist Predicts New Form of Matter� - Technology Review

Topologist Predicts New Form of Matter� - Technology Review: "And topology is about to extend its influence, if Baas has his way. He points out that Borromean rings are just the simplest example of an entire periodic table of topological structures. And if it's possible to make Efimov states that are equivalent to Borromean rings, then it ought to be possible to make the others too.

This family of stuff will be a new state of matter that is governed by news rules, a kind of 'Efimov physics'.

How might this stuff behave? That isn't yet clear but Baas raises an interesting possibility. The deep and unworldly link between particles in Efimov states is remarkably similar to quantum entanglement."

Scientists find unusual electrons that go with the flow

Scientists find unusual electrons that go with the flow: Normally, electron flow in materials is impeded by imperfections -- seemingly slight edges and rifts act like cliffs and crevasses in this microscopic world, blocking electrons in their path. Recent theories, however, predict that electrons on the surface of some compounds containing elements such as antimony can be immune to such disruptions in their flow. The connectivity in their flow, Yazdani said, stems from a special form of electron wave that seemingly alters the pattern of flow around any imperfection.

Physics on the edge

Just a few years ago, no one thought that materials could both insulate and conduct at the same time in this way. “This is a new state of matter — in condensed-matter physics this is the highest goal”

http://www.sciencenews.org/view/feature/id/58909/title/Physics_on_the_edge