Researchers at MIT have achieved a significant breakthrough by identifying the elusive fractional charge effect in a more accessible material: five layers of graphene.
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A sign on the campus of Massachusetts Institute of Technology on July 08, 2020 in Cambridge, Massachusetts.
Self-Sustaining Electron Fractionalization in Graphene
A groundbreaking achievement has been made by researchers at MIT, who have successfully identified the elusive fractional charge effect within a more accessible material: five layers of graphene. Graphene comprises atom-thin layers of carbon.
Through their investigation, researchers from MIT observed that arranging five sheets of graphene in a stair-step configuration fosters an intrinsic environment where electrons can exhibit fractional charges, all without the need for external magnetic fields.
This discovery represents the inaugural observation of the "fractional quantum anomalous Hall effect" in crystalline graphene, a material previously not anticipated to display such behavior. Notably, this effect occurs in the absence of a magnetic field, earning it the designation "anomalous."
MIT's Long Ju uncovered anomalous fractional charge in graphene, a material previously not expected to exhibit such behavior. Their study focused on pentalayer graphene, consisting of five slightly staggered sheets arranged like a staircase.
When cooled to ultracold temperatures, this structure revealed unique electron interactions. Aligning the pentalayer graphene with hexagonal boron nitride (hBN) intensified these interactions, potentially forming a moiré superlattice capable of slowing electrons akin to a magnetic field.
Detecting Fractional Charge
The researchers extracted graphene layers from graphite, arranging them in a step-like configuration. After attaching electrodes, the material was cooled to near absolute zero.
Observing current flow and voltage output, the team detected fractional charge, confirming the presence of this phenomenon within the hybrid graphene structure. This groundbreaking observation validates the potential for novel electronic behavior in graphene configurations.
Ju emphasized graphene's versatility, suggesting its application in diverse electronic systems. Published in Nature, the study marks graphene's debut demonstration of the fractional charge effect and paves the way for further exploration into multilayer graphene's electronic properties.
Back in 1982, researchers stumbled upon the fractional quantum Hall effect in gallium arsenide heterostructures, a groundbreaking discovery that later earned them a Nobel Prize in Physics.
This phenomenon initially confounded scientists due to its unpredictable nature. Employing magnetic fields ten times stronger than those found in MRI machines, researchers managed to slow down electrons to facilitate interactions.
Fast forward to August 2023, scientists at the University of Washington achieved a significant breakthrough by observing fractional charge phenomena in molybdenum ditelluride without needing magnetic fields. The material's unique configuration naturally generated a magnetic field, enabling electron fractionalization.
This "no magnets" revelation opens doors for topological quantum computing, merging the fractional quantum Hall effect with superconductors. Previously deemed nearly unattainable due to conflicting magnetic field requirements, this novel approach now holds promise for enhancing the security of quantum computing.
The fractional charges can serve as qubits, the fundamental units of quantum computation, within a safeguarded topological environment, as per the research team's findings.
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