Quantum discovery: Materials can host D-wave effects with F-wave behaviors
Rice University physicists have shown that immutable topological states, which are highly sought for quantum computing, can be entangled with other, manipulable quantum states in some materials.
“The surprising thing we found is that in a particular kind of crystal lattice, where electrons become stuck, the strongly coupled behavior of electrons in d atomic orbitals actually act like the f orbital systems of some heavy fermions,” said Qimiao Si, co-author of a study about the research in Science Advances.
The unexpected find provides a bridge between subfields of condensed matter physics that have focused on dissimilar emergent properties of quantum materials. In topological materials, for example, patterns of quantum entanglement produce “protected,” immutable states that could be used for quantum computing and spintronics. In strongly correlated materials, the entanglement of billions upon billions of electrons gives rise to behaviors like unconventional superconductivity and the continual magnetic fluctuations in quantum spin liquids.
In the study, Si and co-author Haoyu Hu, a former graduate student in his research group, built and tested a quantum model to explore electron coupling in a “frustrated” lattice arrangement like those found in metals and semimetals that feature “flat bands,” states where electrons become stuck and strongly correlated effects are amplified.
The research is part of an ongoing effort by Si, who won a Vannevar Bush Faculty Fellowship from the Defense Department in July to pursue the validation of a theoretical framework for controlling topological states of matter.
In the study, Si and Hu showed that electrons from d atomic orbitals could become part of larger, molecular orbitals that are shared by several atoms in the lattice. The research also showed that electrons in molecular orbitals could become entangled with other frustrated electrons, producing strongly correlated effects that were very familiar to Si, who has spent years studying heavy fermion materials.
“These are completely d-electron systems,” Si said. “In the d-electron world, it’s like you have a highway with multiple lanes. In the f-electron world, you can think of electrons moving in two tiers. One is like the d-electron highway, and the other is like a dirt road, where movement is very slow.”
Si said f-electron systems host very clean examples of strongly correlated physics, but they aren’t practical for everyday use. More