IMAGE: Qimiao Si is Professor of Physics and Astronomy Harry C. and Olga K. Wiess at Rice University and director of the Rice Center for Quantum Materials. view more
Credit: Photo by Jeff Fitlow / Rice University
HOUSTON – (Jan. 25, 2021) – There might not have been a new theory that could explain how superconductivity arose abnormally in a diverse set of compounds without the physics of Qimiao Si and Emilian Nica have chosen a different name for their 2017 model of orbital-Select superconductivity.
In a study published this month in Stuthan Quantum npj, Si of Rice University and Nica of Arizona State University argue that abnormal superconductivity in some iron-based and heavy-fermion-based materials arises from a common phenomenon known as “multiorbital singlet pairing.”
In superconductors, electrons form pairs and flow effortlessly. Physicists cannot fully explain how pairs form in unconventional superconductors, where quantum forces cause strange behaviors. Heavy fermions, another quantum material, produce electrons that are likely to be thousands of times larger than normal electrons.
Si and Nica proposed the idea of selective pairs within atomic orbitals in 2017 to explain abnormal superconductivity in alkaline iron selenides. The following year, they applied the orbital-selective model in the heavy fermion material in which abnormal superconductivity was first demonstrated in 1979.
They considered naming the model after a related mathematical phrase made famous by quantum pioneer Wolfgang Pauli, but chose d + da to call it. The name refers to mathematical wave functions that describe quantum states.
“It’s like you have a pair of electrons dancing together,” said Si, Harry C. of Rice and Olga K. Wiess Professor of Physics and Astronomy. “You can identify that dance with s-wave, p-wave and d-wave channels, and d + d refers to two types of e-wave that connect to each other in one.”
In the year following the launch of the d + d module, Si gave many speeches about the work and found that audience members often found the name confused with “d + id,” state name. another couple that physicists have been debating for more than a quarter of a year.
“People would come up to me after a speech and say, ‘Your theory about d + id is very interesting,’ and they meant that as a suggestion, but it happened so often and it bothered me,” said Si, who also runs the Rice Center for Quantum Products (RCQM).
In mid-2019, Si and Nica met over lunch while visiting the Los Alamos National Laboratory, and began sharing stories of the d + d versus d + id upheaval.
“That sparked a debate over whether d + da could be meaningful to d + id in a meaningful way, and we realized it wasn’t a joke,” said Nica.
The link included d + d twin states and those that made famous when the Nobel laureate discovered the superfluidity of helium-3.
“There are two types of superfluid pair states of molten helium-3, one called grade B and the other grade grade A,” Nica said. “Imperially, grade B is similar to our d + d, while level A is almost like d + id.”
The symbolism became more interesting when discussing mathematics. Physicists use matrix calculations to describe the quantum pair states in helium-3, and this is also true for the d + d model.
“You have a number of different ways to set up that matrix, and we realized that our d + d matrix for the orbital space was like a different form of the d + id matrix that describes a pair of helium-3s instead of spinning, “Nica said.
Si said the associations with helium-3 superfluid twin states have helped advance a fuller description of twin states in both iron-based and heavy-fermion superconductors.
“As Emil and I talked more, we realized that the quarterly schedule for superconducting parking was not infinite,” Si said, referring to the chart that physics uses to real-time paired states. to arrange.
“We use symmetry – such as surface or spin arrangements, or whether time moves against an equal back-up, which is a payback balance – to put twin states on “It was our announcement that d + id would be found on the existing list. You can use the seasonal chart to build it. But d + d, you can’t. It is longer than the seasonal table, because the table does not include orbitals. “
Si said orbitals are important for describing the behavior of materials such as iron-based superconductors and heavy fermions, where “there is a very strong role in electron-electron interconnection.”
“According to our work, the index needs to be expanded to include orbital indexes,” Si said.
The research was supported by a start-up grant from Arizona State University, the Department of Energy (DE-SC0018197), the Welch Foundation (C-1411) and the National Science Foundation (PHY-1607611).
RCQM is a multidisciplinary research effort that leverages the strengths and global partnerships of more than 20 Rice research organizations.
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Links and resources:
DOI an Stuthan Quantum npj paper: 10.1038 / s41535-020-00304-3
A copy of the paper can be found at: https: /
Rice Center for Quantum Products: https: /
High resolution IMAGES is available for download at:
http: // bit.
CAPTION: “Levitation of magnet on top of superconductor 2” by Jubobroff, Fbouquet, LPS is licensed under CC BY-SA 3.0.
http: // news.
CAPAL: Qimiao Si is Professor of Physics and Astronomy Harry C. and Olga K. Wiess at Rice University and director of the Rice Center for Quantum Materials. (Photo by Jeff Fitlow / Rice University)
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CAPTION: Emilian Nica is a graduate research scholar in physics at Arizona State University. (Image courtesy of E. Nica)
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