Physicists at MIT have made a groundbreaking discovery that sheds light on the transition of certain superconductors into a superconducting state. Their findings provide fresh insights that could enhance existing superconductors and pave the way for the discovery of unconventional ones.
The researchers focused on iron selenide (FeSe), a two-dimensional material known for its high-temperature superconductivity. Unlike other iron-based superconductors, iron selenide undergoes a unique transition involving a collective shift in the orbital energy of atoms, rather than their spins. This discovery introduces new possibilities for uncovering unconventional superconductors.
Superconductivity is observed when certain materials undergo a structural shift, known as a “nematic transition,” under specific conditions, typically at extremely low temperatures. This transition enables the flow of electrons without any resistance, offering various practical applications. Understanding the driving force behind this transition is crucial for improving current superconductors and identifying new ones.
The MIT team identified the key mechanism behind the nematic transition in a specific class of superconductors, which contradicts the previously assumed understanding. While scientists believed that coordinated shifts in magnetic spins drive the transition in iron-based superconductors, the researchers found that iron selenide undergoes a collective shift in orbital energy instead. This subtle but significant distinction presents a fresh avenue for realizing superconducting states.
The study, published in the journal Nature Materials on June 22, involved extensive research on iron selenide. By physically stretching ultrathin samples of the material, the team observed a coordinated shift in the atoms’ orbitals. This shift indicated a clear mechanism of nematicity and the emergence of superconductivity. The researchers used ultrabright X-rays to track the movement of atoms and the behavior of electrons in each sample.
Iron selenide’s behavior stands out among other materials, as it lacks coordinated magnetic behavior despite exhibiting the highest transition temperature among iron-based superconductors. Understanding the origin of nematicity in iron selenide requires a detailed examination of electron arrangements around iron atoms and the consequences of atomic stretching.
The researchers emphasized that their study challenges the prevailing consensus on the driving force behind nematicity and highlights the existence of different underlying physics for spin and orbital nematicity. They anticipate a continuum of materials that bridge the two categories, which could offer promising avenues for discovering new superconductors.
The research was supported by the Department of Energy, the Air Force Office of Scientific Research, and the National Science Foundation. The findings hold significant potential for the development of real-world applications, such as more efficient MRI machines and high-speed, magnetically levitating trains.
Frequently Asked Questions (FAQs) about superconductivity
What did the MIT physicists discover about superconductivity in iron selenide?
The MIT physicists discovered a new mechanism for superconductivity in iron selenide. Unlike other iron-based superconductors, the transition in iron selenide involves a collective shift in atoms’ orbital energy, rather than their spins. This finding challenges previous assumptions and opens up possibilities for unconventional superconductors.
How does the nematic transition contribute to superconductivity?
Under certain conditions, materials undergo a structural shift called a nematic transition, which can unlock superconducting behavior. This transition allows electrons to flow without resistance. Physicists believe that understanding the driving force behind the nematic transition is essential for improving existing superconductors and discovering new ones.
What distinguishes iron selenide from other superconductors?
Iron selenide stands out because it exhibits a nematic transition without coordinated magnetic behavior. Unlike other iron-based superconductors, its transition involves a collective shift in orbital energy rather than spins. Additionally, iron selenide has the highest transition temperature among iron-based superconductors, making it a promising candidate for practical applications.
How did the MIT researchers make their discovery?
The MIT researchers studied ultrathin samples of iron selenide, physically stretching them to mimic the structural stretching during a nematic transition. By using ultrabright X-rays, they tracked the movement of atoms and the behavior of electrons. They observed a coordinated shift in the atoms’ orbitals, indicating a clear mechanism of nematicity and the emergence of superconductivity.
What are the implications of this discovery?
The discovery challenges the consensus about the driving force behind nematicity in superconductors. It suggests that there are different underlying physics for spin and orbital nematicity, expanding the possibilities for finding new superconducting materials. The findings have the potential to enhance current superconductors and open doors to unconventional superconductivity applications in various fields.
More about superconductivity
- MIT News: Physicists Discover a New Switch for Superconductivity
- Nature Materials: Spontaneous orbital polarization in the nematic phase of FeSe