MIT physicists have taken a step toward understanding the puzzling nature of high-temperature superconductors, materials that conduct electricity with no resistance at temperatures well above absolute zero.
If superconductors could be made to work at temperatures as high as room temperature, they could have potentially limitless applications. But first, scientists need to learn much more about how such materials work.
Using a new method, the MIT team made a surprising discovery that may overturn theories about the state of matter in which superconducting materials exist just before they start to superconduct. The findings are reported in the February issue of Nature Physics.
Understanding high-temperature superconductors is one of the biggest challenges in physics today, according to Eric Hudson, MIT assistant professor of physics and senior author of the paper.
Most superconductors only superconduct at temperatures near absolute zero, but about 20 years ago, it was discovered that some ceramics can superconduct at higher temperatures (but usually still below 100 Kelvin, or -173 Celsius).
Such high-temperature superconductors are now beginning to be used for many applications, including cell-phone base stations and a demo magnetic-levitation train. But their potential applications could be much broader.
"If you could make superconductors work at room temperature, then the applications are endless," said Hudson.
Superconductors are superior to ordinary metal conductors such as copper because current doesn't lose energy as wasteful heat as it flows through them, thus allowing larger current densities. Once a current is set in motion in a closed loop of superconducting material, it will flow forever.
In the Nature Physics study, the MIT researchers looked at a state of matter that superconductors inhabit just above the temperature at which they start to superconduct.
When a material is in a superconducting state, all electrons are at the same energy level. The range of surrounding, unavailable electron energy levels is called the superconducting gap. It is a critical component of superconduction, because it prevents electrons from scattering, thus eliminating resistance and allowing the unimpeded flow of current.
Just above the transition temperature when a material starts to superconduct, it exists in a state called the pseudogap. This state of matter is not at all well understood, said Hudson.
The researchers decided to investigate the nature of the pseudogap state by studying the properties of electron states that were believed to be defined by the characteristics of superconductors: the states surrounding impurities in the material.
It had already been shown that natural impurities in a superconducting material, such as a missing or replaced atom, allow electrons to reach energy levels that are normally within the superconducting gap, so they can scatter. This can be observed using scanning tunneling microscopy (STM).
The new MIT study shows that scattering by impurities occurs when a material is in the pseudogap state as well as the superconducting state. That finding challenges the theory that the pseudogap is only a precursor state to the superconductive state, and offers evidence that the two states may coexist.
This method of comparing the pseudogap and superconducting state using STM could help physicists understand why certain materials are able to superconduct at such relatively high temperatures, said Hudson.
"Trying to understand what the pseudogap state is is a major outstanding question," he said.
Lead author of the paper is Kamalesh Chatterjee, a graduate student in physics. MIT physics graduate students Michael Boyer and William Wise are also authors of the paper, along with Takeshi Kondo of the Ames Laboratory at Iowa State University and T. Takeuchi and H. Ikuta of Nagoya University, Japan.
The research was funded by the National Science Foundation and the Research Corporation. Written by Anne Trafton, MIT News Office
Elizabeth A. Thomson | MIT News Office
Magnetic nano-imaging on a table top
20.04.2018 | Georg-August-Universität Göttingen
New record on squeezing light to one atom: Atomic Lego guides light below one nanometer
20.04.2018 | ICFO-The Institute of Photonic Sciences
University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.
Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.
Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.
Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...
Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.
The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...
Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.
Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...
In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...
13.04.2018 | Event News
12.04.2018 | Event News
09.04.2018 | Event News
20.04.2018 | Physics and Astronomy
20.04.2018 | Interdisciplinary Research
20.04.2018 | Physics and Astronomy