Follow Antia Botanaprofessor of physics at Arizona State University.
The quantum phenomena that Antia Botana studies occur on the smallest known scale and can only be discovered obliviously by physical experiments. Botana uses computer simulations to make predictions, help explain experiments, and infer the behavior and dynamics of materials like infinite nickel.
“As theorists, we often fail to predict new superconductors,” she said.
In 2021, however, she experienced the highlight of her early career. Working with experimentalist Julia Mundy at Harvard University, she discovered a new type of superconducting material — four-layer nickel. They reported their findings in Natural materials.
“It was one of the best moments of my life,” Botana recalls. “I was flying back from Spain, and I received a text from collaborator Julia Mundy while I was on leave. When I see the resistivity drop to 0 – nothing better than that”.
Botanica has been chosen as 2022 Sloan Researcher. Her research is supported by a CAREER AWARDS from the National Science Foundation (NSF).
Electronic phase diagram and structural description of layered nickels. A: Graph phase diagram for the electronic phases of coke (top) and nickel (bottom). B: Crystal structures of five-layer nickel in the Nd6Ni5O16 Ruddlesden – Popper phase (left) and Nd6Ni5O12 reduced square planar phase (right), depicted at the same scale. Image credit: Botanica et al
“GS. Botana is one of the most influential theorists in the field of unusual superconductivity, especially layered nickels that have received tremendous interest from the condensed matter and materials community,” said Serdar Ogut. , said program director of the Materials Research Department at National Science. Establish. “I expect that her pioneering theoretical studies, in collaboration with leading experimentalists in the US, will continue to push the boundaries, leading to the discovery of superconducting materials. novel and uncovering the underlying mechanisms that may one day pave the way for room-temperature superconductivity. ”
Superconductivity is the phenomenon that occurs when electrons form pairs rather than moving in isolation, repelling all magnetism and allowing electrons to move without loss of energy. Developing room-temperature superconductors will enable lossless power transmission and faster, cheaper quantum computers. The study of these materials is the domain of condensed matter theory.
“We try to understand what are called quantum materials – materials where everything classical we learned during college disintegrates and no one understands why they do these things. fun they do,” Botana joked.
She started investigating nickellargely, to better understand cuprate – a copper oxide-based superconductor first discovered in 1986. Thirty years on, the mechanism underlying the superconductivity in these materials remains controversial. acrimonious.
Botanica approaches the problem by looking at materials that look like cups. “Copper and nickel are right next to each other on the periodic table,” she said. “This is an obvious thing to do, so people have been looking at nickel for a long time without success.”
But then, in 2019, a team from Stanford discovered superconductivity in nickel, although it has been ‘doped,’ or chemically altered to improve its electronic properties. “The material they found in 2019 is part of a larger family, which is what we wanted because it allows us to compare cups in a better way,” she said.
Botanica’s discovery in 2021 builds on that foundation, using an undoped form of nickel with a unique, flat, multi-layered structure. She decided to investigate this particular form of nickel – a rare-earth, five-fold, square-shaped nickel – based on intuition.
“Having played with many different materials over the years, that is the kind of intuition that people who study electronic structures develop,” she said. “I’ve seen that over the years with my mentors.”
Identifying another form of superconducting nickel allows researchers to find similarities and differences between nickels and between nickel and coke. To date, the more nickels studied, the more cuprate they resemble.
“The phase diagram looks pretty similar. The electron pairing mechanism seems to be the same,” Botana said, “but this is an unresolved question. “
Conventional superconductors exhibit s-wave coupling – electrons can pair in any direction and can be stacked, so the wave is a sphere. On the other hand, nickel is capable of displaying d-wave pairing, which means that a cloud-like quantum wave depicts paired electrons shaped like a four-leaf clover. Another important difference is the degree of overlap of oxygen and transition metals in these materials. Cuprat exhibits a large ‘super-exchanger’ – the material exchanges electrons in the copper atom via an oxygen-containing pathway, rather than directly.
“We think that might be one of the factors that governs superconductivity and causes nickel’s lower critical temperature,” she said. “We can find a way to optimize that feature.”
Botana and colleagues Kwan-Woo Lee, Michael R. Norman, Victor Pardo and Warren E. Pickett described some of these differences in a review paper for Boundaries in Physics in February 2022.
FINDING THE ROOT CAUSE OF SUPER PERFORMANCE
Write in Physical Assessment X In March 2022, Botana and colleagues from Brookhaven National Laboratory and Argonne National Laboratory further investigated the role of oxygen states in low valence nickel, La4Ni3O8. Using computational and experimental methods, they compared the material with a similar electron-filled prototype cup. This work is unique in that it directly measures the energy of the Nickel-Oxygen hybrid state.
They found that although more energy is needed to transfer the charge, nickel retains a sizable superexchange capacity. They concluded that both the “Coulomb interaction” (the attraction or repulsion of particles or objects because they carry electricity) and the transfer of charge should be considered when explaining the properties of nickel.
The quantum phenomena that Botana studied occur on the smallest known scale and can only be discovered obliquely by physical experiment (as in Physical Review X paper). Botana uses computer simulations to make predictions, help explain experiments, and infer the behavior and dynamics of materials like infinite nickel.
Her research uses Density functional theoryor DFT – a computational means of solving the Schrödinger equation describing the wave function of a quantum mechanical system – as well as a newer, more precise branch called dynamic mean field theory can handle closely correlated electrons.
To conduct her research, Botana uses the Texas Advanced Computing Center (TACC) Stampede2 supercomputer – the second fastest at any university in the US – as well as machines at Arizona State University. Even on the world’s fastest supercomputers, studying quantum materials is not a simple matter.
“If I see a problem with too many atoms, I say, ‘I can’t study that. “Twenty years ago, a few atoms might have looked like too much.” But more powerful supercomputers are allowing physicists to study larger, more complex systems – like nickel – and add tools, like moving average field theory, that can better capture the behavior micro-quantum.
Botana says, despite living in the Golden Age of Discovery, the field of condensed matter physics still doesn’t get the reputation it deserves.
“Your phone or computer would be unusable without research into condensed matter physics – from the screen to the battery, to the tiny camera. It is important for the public to understand that even if it is basic research, and even if researchers do not know how it will be used later, this type of documentary research is still very important. important “.
Source: TACC
