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Back in 2008, a surprising discovery was made and it revealed that iron-based materials have a high-temperature superconductivity. The uncovering of this property astounded scientists, as it had long been believed that iron hindered superconductivity due to competition between the dynamic formation of electron pairs and the static ordering of electron spins.
High Temperature Superconductors
Traditional high temperature superconductors are based on copper, and research into this material and its properties have been an intense point of interest over the last two decades since their discovery. While the research has been fruitful, there have been many experimentally relevant problems left unsolved, mostly those relating to surpassing the superconducting critical temperature. The discovery of iron as a high-temperature superconductor has opened the door to re-exploring these problems with new material with different superconducting dynamics.
Since this critical discovery, an explosion of studies worldwide has taken place in order to explore the fundamental mechanisms of iron as a high temperature superconductor, in order to gain an understanding of how it works and ultimately, what its real world applications may be. Given that iron has a relatively high critical temperature as well as high field properties, a vast amount of studies have been conducted which focus on uncovering the potential applications of iron-based materials used as superconductors.
The New Iron Age
This revelation has led to what has been coined ‘the new iron age’, due to the elevated interest in research into iron leading to rapid developments into the use of it as a superconductor. Much time and money is currently being invested in projects that dive into the workings of iron as a superconductor. For example, a team at Cornell University have built a custom Spectroscopic Imaging Scanning Tunneling Microscope in order to use it to investigate electron-activity within iron-based superconductors, to gain an understanding of how they work.
One key focus of this research is to figure out a way to get the superconductor to work at room temperature. Currently, the research is very expensive and energy consuming, as conditions to study the materials must be lower than -100 degrees Celsius. This also brings the problem that superconductors are looked on as a way to transmit electricity in order to save on energy, but the cooling they require would use up more energy than it would be saving, making it not economically viable.
In addition, there are other questions which remain unanswered. Scientists know that the total spin of the Fe ion is either 1 or 2 because it has six electrons in the 3d orbitals. However, the SDW magnetic moment has been observed not to match up using a strong correlation model. There needs to be a new model developed to understand the magnetism of iron superconductors.
Spin-Density Wave and Superconductivity
Further to this, researchers are looking to understand whether the spin-density wave and superconductivity compete with one another, or if they coexist. They are also looking to find out whether, as in the cuprates (copper-based superconductors), a pseudogap phase exists above the superconducting state of these materials. Answering these questions will allow scientists to understand not only iron-based superconductors, but it will also reveal the relationship between kinetic energy and interaction energy in condensed-matter physics in general and this is what will propel the new Iron Age.
The exploration will continue into the future, as scientists strive to understand the full capabilities of iron as a superconductor. As we have seen it may hold the key to many important problems, but before then, scientists must work hard to research several areas in particular which are still without a full understanding.
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