From Lawrence Berkeley National Lab: “Topological Matters: Toward a New Kind of Transistor”

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From Lawrence Berkeley National Lab

December 10, 2018
Glenn Roberts Jr.
(510) 486-5582

X-ray experiments at Berkeley Lab provide first demonstration of room temperature switching in ultrathin material that could serve as a ‘topological transistor’.

James Collins, a researcher at Monash University in Australia, works on an experiment at Beamline 10.0.1, part of Berkeley Lab’s Advanced Light Source. (Credit: Marilyn Chung/Berkeley Lab)


Billions of tiny transistors supply the processing power in modern smartphones, controlling the flow of electrons with rapid on-and-off switching.

But continual progress in packing more transistors into smaller devices is pushing toward the physical limits of conventional materials. Common inefficiencies in transistor materials cause energy loss that results in heat buildup and shorter battery life, so researchers are in hot pursuit of alternative materials that allow devices to operate more efficiently at lower power.

Now, an experiment conducted at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has demonstrated, for the first time, electronic switching in an exotic, ultrathin material that can carry a charge with nearly zero loss at room temperature. Researchers demonstrated this switching when subjecting the material to a low-current electric field.

From left to right: Shujie Tang, a postdoctoral researcher at Berkeley Lab’s Advanced Light Source (ALS); Sung-Kwan Mo, an ALS staff scientist; and James Collins and Mark Edmonds, researchers at Monash University, gather during an experiment at ALS Beamline 10.0.1 in November. (Credit: Marilyn Chung/Berkeley Lab)

The team, which was led by researchers at Monash University in Australia and included Berkeley Lab scientists, grew the material from scratch and studied it with X-rays at the Advanced Light Source (ALS) [see above], a facility at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab).

The material, known as sodium bismuthide (Na3Bi), is one of two materials that is known to be a “topological Dirac semimetal,” meaning it has unique electronic properties that can be tuned to behave in different ways – in some cases more like a conventional material and in other cases more like a topological material. Its topological properties were first confirmed in earlier experiments at the ALS.

Topological materials are considered promising candidates for next-generation transistors, and for other electronics and computing applications, because of their potential to reduce energy loss and power consumption in devices. These properties can exist at room temperature – an important distinction from superconductors that require extreme chilling – and can persist even when the materials have structural defects and are subject to stress.

Researchers at Berkeley Lab’s Advanced Light Source used an X-ray technique known as ARPES to produce these images showing the electronic ranges of energy in an ultrathin material. (Credit: Berkeley Lab, Monash University)

Materials with topological properties are the focus of intense research by the global scientific community (see a related article), and in 2016 the Nobel Prize in physics was awarded for theories related to topological properties in materials.

The ease in switching the material studied at the ALS from an electrically conducting state to an insulating, or non-conducting state, bode well for its future transistor applications, said Sung-Kwan Mo, a staff scientist at the ALS who participated in the latest study. The study is detailed in the Dec. 10 edition of the journal Nature.

See the full article here .


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