Material Keyboard

Nanotechnology Breakthrough: A Materials-Keyboard Product of Graphene

Material Keyboard

The fabric keyboard realized by the ETH Zurich researchers. By making use of electrical voltages (“keys”) at totally different factors, the magic-​angle graphene can develop into domestically superconducting (electron pairs) or isolating (barrier on the proper). Credit score: ETH Zurich / F. de Vries

Researchers at ETH Zurich have succeeded in turning specifically ready graphene flakes both into insulators or into superconductors by making use of an electrical voltage. This method even works domestically, which means that in the identical graphene flake areas with utterly totally different bodily properties might be realized aspect by aspect.

The manufacturing of recent digital elements requires supplies with very numerous properties. There are isolators, as an illustration, which don’t conduct electrical present, and superconductors which transport it with none losses. To acquire a selected performance of a part one often has to hitch a number of such supplies collectively. Usually that isn’t simple, specifically when coping with nanostructures which might be in widespread use right this moment.

A staff of researchers at ETH Zurich led by Klaus Ensslin and Thomas Ihn on the Laboratory for Stable State Physics have now succeeded in making a cloth behave alternately as an insulator or as a superconductor – and even as each at totally different places in the identical materials – by merely making use of an electrical voltage. Their outcomes have been revealed within the scientific journal Nature Nanotechnology. The work was supported by the Nationwide Centre of Competence in Analysis QSIT (Quantum Science and Know-how).

Graphene with a magic angle

The fabric Ensslin and his co-​employees use bears the considerably cumbersome identify “Magic Angle Twisted Bilayer Graphene.” In precise reality, this identify hides one thing somewhat easy and well-​recognized, specifically carbon – albeit in a selected type and with a particular twist. The place to begin for the fabric are graphene flakes, that are carbon layers which might be just one atom thick. The researchers put two of these layers on prime of one another in such a method that their crystal axes will not be parallel, however somewhat make a “magic angle” of precisely 1.06 levels. “That’s fairly tough, and we additionally must precisely management the temperature of the flakes throughout manufacturing. In consequence, it typically goes flawed,” explains Peter Rickhaus, who was concerned within the experiments as a postdoc.

In twenty % of the makes an attempt, nonetheless, it really works, and the atomic crystal lattices of the graphene flakes then create a so-​known as moiré sample through which the electrons of the fabric behave otherwise than in bizarre graphene. Moiré patterns are acquainted from tv, as an illustration, the place the interaction between a patterned garment and the scanning strains of the tv picture can result in fascinating optical results. On prime of the magic angle graphene flakes the researchers connect a number of further electrodes which they will use to use an electrical voltage to the fabric. After they then cool every little thing down to a couple hundredths of a level above absolute zero, one thing exceptional occurs. Relying on the utilized voltage, the graphene flakes behave in two utterly reverse methods: both as a superconductor or as an insulator. This switchable superconductivity was already demonstrated in 2018 on the Massachusetts Institute of Know-how (MIT) within the USA. Even right this moment only some teams worldwide are capable of produce such samples.

Josephson Junction

Electron microscope picture of the Josephson junction (false colors). Utilizing the electrodes (vibrant and darkish gold) as piano keys, an insulating layer solely 100 nanometres thick might be created between the 2 superconducting areas. Credit score: ETH Zurich / F. de Vries

Insulator and superconductor in the identical materials

Ensslin and his colleagues are actually going one step additional. By making use of totally different voltages to the person electrodes they flip the magic angle graphene into an insulator in a single spot, however a couple of hundred nanometres to at least one aspect it turns into a superconductor.

“Once we noticed that, we clearly first tried to understand a Josephson junction,” says Fokko de Vries, who can be a postdoc in Ensslins laboratory. In such junctions two superconductors are separated by a wafer-​skinny insulating layer. On this method, present can not movement straight between the 2 superconductors however somewhat has to tunnel quantum mechanically by the insulator. That, in flip, causes the conductivity of the contact to range as a perform of the present in a attribute vogue, relying on whether or not direct or alternating present is used.

Attainable purposes in quantum applied sciences

The ETH researchers managed to supply a Josephson junction contained in the graphene flakes twisted by the magic angle by utilizing totally different voltages utilized to the three electrodes, and in addition to measure its properties. “Now that that’s labored as effectively, we are able to attempt our arms at extra complicated gadgets reminiscent of SQUIDs,” says de Vries. In SQUIDs (“superconducting quantum interference machine”) two Josephson junctions are linked to type a hoop. Sensible purposes of such gadgets embody measurements of tiny magnetic fields, but additionally trendy applied sciences reminiscent of quantum computer systems. For attainable makes use of in quantum computer systems, an fascinating facet is that with the assistance of the electrodes the graphene flakes might be turned not simply into insulators and superconductors, but additionally into magnets or so-​known as topological insulators, through which present can solely movement in a single course alongside the sting of the fabric. This might be exploited to understand totally different sorts of quantum bits (qubits) in a single machine.

A keyboard for supplies

“Up to now, nonetheless, that’s simply hypothesis,” Ensslin says. Nonetheless, he’s enthusiastic in regards to the prospects that come up from {the electrical} management even now. “With the electrodes, we are able to virtually play the piano on the graphene.” Amongst different issues, the physicists hope that this may assist them to achieve new insights into the detailed mechanisms that result in superconductivity in magic angle graphene.

Reference: “Gate-defined Josephson junctions in magic-angle twisted bilayer graphene” by Folkert Okay. de Vries, Elías Portolés, Giulia Zheng, Takashi Taniguchi, Kenji Watanabe, Thomas Ihn, Klaus Ensslin and Peter Rickhaus, 3 Might 2021, Nature Nanotechnology.
DOI: 10.1038/s41565-021-00896-2

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