Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Soundproofing with quantum physics

06.07.2015

Doughnuts, electric current and quantum physics - this will sound like a weird list of words to most people, but for Sebastian Huber it is a job description.

ETH-professor Huber is a theoretical physicist who, for several years now, has focused his attention on so-called topological insulators, i.e., materials whose ability to conduct electric current originates in their topology.


A doughnut can be turned into a coffee cup by pulling, stretching and molding. Topologically speaking, therefore, doughnuts and coffee cups are identical.

Credit: Sebastian Huber / ETH Zurich

The easiest way to understand what "topological" means in this context is to imagine how a doughnut can be turned into a coffee cup by pulling, stretching and moulding - but without cutting it. Topologically speaking, therefore, doughnuts and coffee cups are identical, and by applying the same principle to the quantum mechanical wave function of electrons in a solid one obtains the phenomenon of the topological insulator.

This is advanced quantum physics, highly complex and far removed from everyday experience. Nevertheless, professor Huber and his collaborators have now managed to make these abstract ideas very concrete and even to come up with a possible application in engineering by cutting red tape, as it were, and involving colleagues from different disciplines all the way through the ETH.

From quanta to mechanics

In the beginning, Sebastian Huber asked a simple question: is it possible to apply the principle of a topological insulator to mechanical systems? Normally, quantum physics and mechanics are two separate worlds.

In the quantum world particles can "tunnel" through barriers and reinforce or cancel each other as waves, whereas everyday mechanics deals with falling bodies or the structural analysis of bridges. Huber and his colleagues realized, however, that the mathematical formulas describing the quantum properties of a topological insulator can be rearranged to look exactly like those of a well-known mechanical system - an array of swinging pendulums.

In particular, just like their quantum mechanical counterparts the mechanical formulas predicted so-called edge states. In such states an electric current (or, in the case of pendulums, a mechanical vibration) flows along the edges of the material, while inside the system nothing happens. "From a theoretical point of view that was a beautiful result", says Huber, "but, of course, it is easier to convince people if you also show it in practice."

No sooner said than done, together with technicians at the ETH Huber and his student built a mechanical model consisting of 270 pendulums that are arranged in a rectangular lattice and connected by small springs. Two of those pendulums can be mechanically excited, meaning that they can be shaken back and forth with a particular frequency and strength.

Little by little, the spring couplings cause the other pendulums to start swinging as well. Eventually, for a particular excitation frequency the physicists saw what they had been hoping for: the pendulums inside the rectangle stood still, whereas those along the edge vibrated rhythmically, causing a "wave" to flow around the rectangle. In other words, the coupled pendulums did, indeed, behave just like a topological insulator.

Robotic arms and lenses for sound

What started out as a pipe dream and a nice gimmick for professor Huber could soon become a useful tool. The mechanical edge states of the coupled pendulums, it turns out, are so robust - "topologically protected", in technical language - that they persist if the array of pendulums is disordered and even if a part of the rectangle is removed.

Such properties would be interesting, for instance, in sound and vibration insulation, which is important in various areas such as industrial production, where robot arms have to place objects precisely and without jittering. Moreover, one can imagine materials that convey sound in one direction only, or others that focus sound like a lens.

"Such applications are very challenging, but still realistic", says Chiara Daraio, ETH-professor for mechanics and materials. Of course, the mechanical systems would first have to shrink considerably - Huber's pendulums are, after all, half a metre long and weigh half a kilo. The engineers are already building a new device that works without pendulums and that will only be a few centimetres in size.

###

Literature reference

Süsstrunk R, Huber SD: Observation of phononic helical edge states in a mechanical topological insulator. Science 2015, 349: 47-50, doi: 10.1126/science.aab0239

Media Contact

Dr. Sebastian Huber
sehuber@ethz.ch

 @ETH_en

http://www.ethz.ch/index_EN 

Dr. Sebastian Huber | EurekAlert!

More articles from Physics and Astronomy:

nachricht NASA detects solar flare pulses at Sun and Earth
17.11.2017 | NASA/Goddard Space Flight Center

nachricht Pluto's hydrocarbon haze keeps dwarf planet colder than expected
16.11.2017 | University of California - Santa Cruz

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>