Rice University physicists, in a study led by Skimmion, have connected two subfields of quantum physics by demonstrating that specific immutable topological states critical to quantum computing can be intertwined with variable quantum states in certain materials. This discovery enables potential operations at significantly higher temperatures, offering huge functional prospects.
Rice University physicists have demonstrated that the immutable topological states highly sought after in quantum computing can be entangled with other manipulated quantum states in certain materials.
"The surprising thing we found is that in a special lattice where electrons are trapped, the strongly coupled behavior of electrons in d atomic orbitals actually behaves like the f orbital systems of some heavy fermions," said the authors of a related study in Science Advances.
This unexpected discovery provides a bridge between subfields of condensed matter physics that focus on different emergent properties of quantum materials. For example, in topological materials, quantum entangled patterns produce "protected", immutable states that can be used in quantum computing and spintronics. The entanglement of billions of electrons in strongly correlated materials can produce behaviors such as unconventional superconductivity and sustained magnetic fluctuations in quantum spin liquids.
In the study, Shi Qimiao and co-author Haoyu Hu, a former graduate student in his research group, built and tested a quantum model to explore electron coupling in "frustrated" lattice arrangements, like those found in metals and semimetals with "flat-band" characteristics, suggesting that electrons become stuck and strong correlation effects are amplified.
The research is part of an ongoing effort by Skimmion, who was awarded the U.S. Department of Defense's prestigious Vannevar Bush Faculty Fellowship in July, to validate theoretical frameworks for controlling topological states of matter.
In this study, Shi Qimiao and Hu Haoyu showed that electrons from d atomic orbitals can become part of larger molecular orbitals shared by multiple atoms in the crystal lattice. The research also shows that electrons in molecular orbitals may become entangled with other frustrated electrons, creating strong correlation effects, which is very familiar to Si, which has studied heavy fermion materials for many years.
"These are completely d-electronic systems," Schimiao said. "In the world of d-electrons, it's like there's a multi-lane highway. In the world of f-electrons, you can think of electrons moving in two layers. One is like a d-electron highway, and the other is like a dirt road, moving very slowly."
Si says f-electronic systems have very clear physical examples of strong correlations, but they are not suitable for everyday use.
“This dirt road is too far from the highway,” he said. "Highway effects are very small, which means tiny energy scales and very low physical temperatures. That means you need to get to temperatures around 10 Kelvin to see the effects of coupling. That's not the case in the delectronic world. On multi-lane highways, things are coupling very efficiently."
Even if the frequency band is flat, the coupling efficiency still exists. Si likened it to one lane of a highway becoming as inefficient and slow as a dirt road.
"Even though it has become a dirt road, it still shares status with the other lanes because they all come from the D-track," Si said. "It's actually a dirt road, but it's more coupled, and that translates into physics at higher temperatures. That means I can have all the exquisite physics based on f electrons, for which I have well-defined models and a lot of intuition from years of research, but instead of having to go to 10 Kelvin, I can work at, say, 200 Kelvin, maybe even 300 Kelvin, or room temperature. So from a functional perspective, it's very promising."