On the hunt for new and peculiar superconductors

October 31, 2017 by Henrik Möller
On the hunt for new and peculiar superconductors
Annica Black-Schaffer is one of four ERC Starting Grant recipients at Uppsala University. Credit: Mikael Wallerstedt

Annica Black-Schaffer wants to understand unconventional superconductors. The fact that she recently received the prestigious ERC Starting Grant and is a former recipient of grants from the Knut and Alice Wallenberg Foundation is a testament to the interest in her research. One beckoning application is tomorrow's supercomputers.

Superconductors are materials which, at , conduct currents with no resistance and without releasing heat. The phenomenon was discovered in 1911 and now has applications such as MRIs, where the necessary cooling is done with helium.

"What I want is to understand unconventional, rather unusual and their properties and consequences," says Annica Black-Schaffer, senior lecturer and associate professor in materials theory at the Department of Physics and Astronomy.

One example is topological superconductors. Topology in physics is used to describe how a material's properties change and enter different states under different conditions and temperatures, discoveries which gave David Thouless, Duncan Haldane and Michael Kosterlitz the 2016 Nobel Prize in Physics.

Different quantum mechanical wave function

Annica Black-Schaffer explains that in , the quantum mechanical wave function of electrons is different.

"They are superconductors, but they have a metallic condition at the edge or surface. This phenomenon gives rise to majorana fermions which, put simply, are half electrons. An electron is really a fundamental particle that cannot be split up. But in these materials, the electrons have two completely separate parts. It's exactly as if the electron were in two different places at the same time!"

If majorana fermions can also be twisted and caused to change places, then Annica Black-Schaffer and her colleagues may theoretically be on to the solution for a durable quantum computer. In a quantum computer, information is handled in qubits, or quantum bits. A qubit can be a one and zero at the same time, which makes calculations far faster than today's computers, but they are simultaneously much more sensitive to disturbances such as vibrations or temperature changes. The properties of majorana fermions allow a computer to evade this sensitivity.

Mapping properties of materials

She emphasizes that her research is purely theoretical basic research. However, experiments are already underway in several parts of the world, some of which are sponsored by a large software company.

"What we're doing is mapping the properties of the materials and calculating when the appear and under what circumstances."

With initial funding from ERC of SEK 15 million behind her, Annica Black-Schaffer can now continue and also study even more with odd frequency dependencies. Electrons, which otherwise avoid one another due to a negative charge, form pairs under superconductivity.

"But some materials have a time dependence between both of the electrons, and then odd-frequency superconductivity can arise," explains Annica Black-Schaffer.

Theorists and experimentalists

There are many more such which she and her research group now want to discover and study. One new material they have already found is strontium ruthenate, which is a well-known superconductor with very special properties. Another interim goal is to understand in greater depth what odd-frequency superconductors are, and their experimental consequences.

"As theorists, it is exciting to see what experimentalists make of our models in practice. Or the reverse – they can discover a phenomenon that we sink our teeth into, in an effort to explain it!"

Explore further: Spin-polarized surface states in superconductors

Related Stories

Spin-polarized surface states in superconductors

October 26, 2017

When it comes to entirely new, faster, more powerful computers, Majorana fermions may be the answer. These hypothetical particles can do a better job than conventional quantum bits (qubits) of light or matter. Why? Because ...

Scientists explain the theory behind Ising superconductivity

November 23, 2015

Superconductivity is a fascinating quantum phenomenon in which electrons form pairs and flow with zero resistance. However, strong enough magnetic field can break electron pairs and destroy superconductivity. Surprisingly, ...

Majorana highway on a chip

July 7, 2017

The first experimental evidence of a Majorana fermion in Delft 2012 led to a wave of scientific enthusiasm: control such particles are a holy grail in quantum science and technology. Quantum chips based on Majorana fermions ...

Recommended for you

How the Earth stops high-energy neutrinos in their tracks

November 22, 2017

Neutrinos are abundant subatomic particles that are famous for passing through anything and everything, only very rarely interacting with matter. About 100 trillion neutrinos pass through your body every second. Now, scientists ...

Lightning, with a chance of antimatter

November 22, 2017

A storm system approaches: the sky darkens, and the low rumble of thunder echoes from the horizon. Then without warning... Flash! Crash!—lightning has struck.

Quantum internet goes hybrid

November 22, 2017

In a recent study published in Nature, ICFO researchers led by ICREA Prof. Hugues de Riedmatten report an elementary "hybrid" quantum network link and demonstrate photonic quantum communication between two distinct quantum ...

Enhancing the quantum sensing capabilities of diamond

November 22, 2017

Researchers have discovered that dense ensembles of quantum spins can be created in diamond with high resolution using an electron microscopes, paving the way for enhanced sensors and resources for quantum technologies.

Study shows how to get sprayed metal coatings to stick

November 21, 2017

When bonding two pieces of metal, either the metals must melt a bit where they meet or some molten metal must be introduced between the pieces. A solid bond then forms when the metal solidifies again. But researchers at MIT ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

KBK
not rated yet Nov 01, 2017
A half electron by it's nature is temporally indistinct.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.