A world research team led by Lawrence Berkeley National Laboratory (Berkeley Lab) has taken the primary atomic-resolution images and demonstrated electrical control of a chiral interface state — an exotic quantum phenomenon that might help researchers advance quantum computing and energy-efficient electronics.
The chiral interface state is a conducting channel that permits electrons to travel in just one direction, stopping them from being scattered backwards and causing energy-wasting electrical resistance. Researchers are working to raised understand the properties of chiral interface states in real materials but visualizing their spatial characteristics has proved to be exceptionally difficult.
But now, for the primary time, atomic-resolution images captured by a research team at Berkeley Lab and UC Berkeley have directly visualized a chiral interface state. The researchers also demonstrated on-demand creation of those resistance-free conducting channels in a 2D insulator.
Their work, which was reported within the journal Nature Physics, is a component of Berkeley Lab’s broader push to advance quantum computing and other quantum information system applications, including the design and synthesis of quantum materials to handle pressing technological needs.
“Previous experiments have demonstrated that chiral interface states exist, but nobody has ever visualized them with such high resolution. Our work shows for the primary time what these 1D states appear to be on the atomic scale, including how we are able to alter them — and even create them,” said first writer Canxun Zhang, a former graduate student researcher in Berkeley Lab’s Materials Sciences Division and the Department of Physics at UC Berkeley. He’s now a postdoctoral researcher at UC Santa Barbara.
Chiral interface states can occur in certain kinds of 2D materials referred to as quantum anomalous Hall (QAH) insulators which can be insulators in bulk but conduct electrons without resistance at one-dimensional “edges” — the physical boundaries of the fabric and interfaces with other materials.
To organize chiral interface states, the team worked at Berkeley Lab’s Molecular Foundry to fabricate a tool called twisted monolayer-bilayer graphene, which is a stack of two atomically thin layers of graphene rotated precisely relative to at least one one other, making a moiré superlattice that exhibits the QAH effect.
In subsequent experiments on the UC Berkeley Department of Physics, the researchers used a scanning tunneling microscope (STM) to detect different electronic states within the sample, allowing them to visualise the wavefunction of the chiral interface state. Other experiments showed that the chiral interface state will be moved across the sample by modulating the voltage on a gate electrode placed underneath the graphene layers. In a final demonstration of control, the researchers showed that a voltage pulse from the tip of an STM probe can “write” a chiral interface state into the sample, erase it, and even rewrite a brand new one where electrons flow in the other way.
The findings may help researchers construct tunable networks of electron channels with promise for energy-efficient microelectronics and low-power magnetic memory devices in the long run, and for quantum computation making use of the exotic electron behaviors in QAH insulators.
The researchers intend to make use of their technique to check more exotic physics in related materials, reminiscent of anyons, a brand new sort of quasiparticle that might enable a path to quantum computation.
“Our results provide information that wasn’t possible before. There continues to be an extended method to go, but that is a very good first step,” Zhang said.
The work was led by Michael Crommie,a senior faculty scientist in Berkeley Lab’s Materials Sciences Division and physics professor at UC Berkeley.
Tiancong Zhu, a former postdoctoral researcher within the Crommie group at Berkeley Lab and UC Berkeley, contributed as co-corresponding writer and is now a physics professor at Purdue University.
The Molecular Foundry is a DOE Office of Science user facility at Berkeley Lab.
This work was supported by the DOE Office of Science. Additional funding was provided by the National Science Foundation.
