When layers of “magic-angle” graphene (bottom) come in contact with layers of specific shifts metals, it causes a phenomenon called spin-orbit coupling in the graphene layers. Magic-angle graphene has triggered rather a stir in physics in recent years. To do that, Li and his team interfaced magic-angle graphene with a block of tungsten diselenide, a material that has strong spin-orbit coupling. Aligning the stack precisely causes spin-orbit coupling in the graphene. The group discovered that the magnetic homes of magic-angle graphene can be controlled with both external electrical fields and magnetic fields.
” Magnetism and superconductivity are generally at opposite ends of the spectrum in condensed matter physics, and its uncommon for them to appear in the very same material platform,” stated Jia Li, an assistant teacher of physics at Brown and senior author of the research study. “Yet weve revealed that we can produce magnetism in a system that initially hosts superconductivity. This gives us a brand-new method to study the interplay between superconductivity and magnetism, and provides amazing brand-new possibilities for quantum science research study.”
Magic-angle graphene has triggered quite a stir in physics recently. Graphene is a two-dimensional material made of carbon atoms arranged in a honeycomb-like pattern. Single sheets of graphene are intriguing by themselves– displaying remarkable product strength and incredibly efficient electrical conductance. Things get even more interesting when graphene sheets are stacked. Electrons begin to connect not only with other electrons within a graphene sheet, but likewise with those in the adjacent sheet. Changing the angle of the sheets with regard to each other changes those interactions, triggering fascinating quantum phenomena like superconductivity.
This brand-new research adds a new wrinkle– spin-orbit coupling– to this currently interesting system. Spin-orbit coupling is a state of electron habits in certain products in which each electrons spin– its tiny magnetic moment that points either up or down– becomes connected to its orbit around the atomic nucleus.
” We understand that spin-orbit coupling triggers a broad range of interesting quantum phenomena, but its not typically present in magic-angle graphene,” said Jiang-Xiazi Lin, a postdoctoral researcher at Brown and the studys lead author. “We wanted to introduce spin-orbit coupling, and after that see what impact it had on the system.”
To do that, Li and his group interfaced magic-angle graphene with a block of tungsten diselenide, a material that has strong spin-orbit coupling. Lining up the stack specifically induces spin-orbit coupling in the graphene. From there, the team probed the system with external electrical currents and magnetic fields.
The experiments revealed that an electrical current flowing in one direction across the material in the existence of an external magnetic field produces a voltage in the instructions perpendicular to the present. That voltage, understood as the Hall result, is the telltale signature of an intrinsic magnetic field in the material.
Much to the research study teams surprise, they showed that the magnetic state could be managed using an external electromagnetic field, which is oriented either in the aircraft of the graphene or out-of-plane. This remains in contrast with magnetic products without spin-orbit coupling, where the intrinsic magnetism can be managed only when the external magnetic field is lined up along the direction of the magnetism.
” This observation is an indication that spin-orbit coupling is undoubtedly present and offered the idea for constructing a theoretical model to comprehend the influence of the atomic user interface,” said Yahui Zhang, a theoretical physicist from Harvard University who dealt with the group at Brown to understand the physics connected with the observed magnetism.
” The unique impact of spin-orbit coupling offers researchers a brand-new speculative knob to turn in the effort to comprehend the behavior of magic-angle graphene,” said Erin Morrissette, a Brown college student who performed a few of the experimental work. “The findings likewise have the capacity for brand-new gadget applications.”
One possible application is in computer system memory. The team found that the magnetic homes of magic-angle graphene can be controlled with both external electromagnetic fields and electric fields. That would make this two-dimensional system a perfect prospect for a magnetic memory device with flexible read/write choices.
The issue, however, is that such an interface is tough to create due to the fact that magnets are generally damaging to superconductivity. A material thats capable of both ferromagnetism and superconductivity might supply a way to create that interface.
” We are dealing with utilizing the atomic interface to stabilize superconductivity and ferromagnetism at the very same time,” Li said. “The coexistence of these 2 phenomena is uncommon in physics, and it will certainly open more excitement.”
Referral: “Spin-orbit– driven ferromagnetism at half moiré completing magic-angle twisted bilayer graphene” by Jiang-Xiazi Lin, Ya-Hui Zhang, Erin Morissette, Zhi Wang, Song Liu, Daniel Rhodes, K. Watanabe, T. Taniguchi, James Hone and J. I. A. Li, 6 January 2022, Science.DOI: 10.1126/ science.abh2889.
The research study was primarily supported by Brown University. Additional co-authors are Ya-Hui Zhang, Zhi Wang, Song Liu, Daniel Rhodes, Kenji Watanabe, Takashi Taniguchi and James Hone.
When layers of “magic-angle” graphene (bottom) are available in contact with layers of specific transitions metals, it causes a phenomenon called spin-orbit coupling in the graphene layers. That phenomenon offers rise to unexpected physics, including ferromagnetism. Credit: Li lab/Brown University
Magnets and superconductors dont typically get along, but a new research study reveals that magic-angle graphene is capable of producing both superconductivity and ferromagnetism, which could be beneficial in quantum computing.
When 2 sheets of the carbon nanomaterial graphene are stacked together at a specific angle with regard to each other, it offers increase to some fascinating physics. For example, when this so-called “magic-angle graphene” is cooled to near outright absolutely no, it all of a sudden ends up being a superconductor, implying it conducts electrical power with no resistance.
Now, a research study group from Brown University has actually discovered a surprising new phenomenon that can arise in magic-angle graphene. In research released in the journal Science, the group revealed that by causing a phenomenon referred to as spin-orbit coupling, magic-angle graphene becomes a powerful ferromagnet.
