NUS scientists have discovered how to manipulate many body states in thin semiconductors by encapsulating them in atomically thin materials and changing the electric field
Scientists at the National University of Singapore (NUS) have demonstrated a new way of controlling many body states in correlated electron systems by confining them in a device made out of atomically thin materials, and applying external electric and magnetic fields. This research, published on 23 December 2015 in the prestigious scientific journal Nature, was led by Professor Antonio Castro Neto and his research team at the Centre for Advanced 2D Materials (CA2DM) of the NUS Faculty of Science.
Almost all modern technology like motors, light bulbs and semiconductor chips runs on electricity, harnessing the flow of electrons through devices. Explained Prof Castro Neto, “Not only are electrons small and fast, they naturally repel each other due to their electric charge. They obey the strange laws of quantum physics, making it difficult to control their motion directly.”
To control electron behaviour, many semi-conductor materials require chemical doping, where small amounts of a foreign material are embedded in the material to either release or absorb electrons, creating a change in the electron concentration that can in turn be used to drive currents.
However, chemical doping has limitations as a research technique, since it causes irreversible chemical change in the material being studied. The foreign atoms embedded into the material also disrupt its natural ordering, often masking important electronic states of the pure material.
The NUS research team was able to replicate the effects of chemical doping in this study by using only external electric and magnetic fields applied to an atomically thin material, titanium diselenide (TiSe2), encapsulated with boron-nitride (hBN). The researchers were able to control the behaviour of the electrons accurately and reversibly, making measurements that had been theoretical up to now. The thinness of the two materials was crucial, confining the electrons within the material to a two-dimensional layer, over which the electric and magnetic fields had a strong, uniform effect.
“In particular, we could also drive the material into a state called superconductivity, in which electrons move throughout the material without any heat or energy loss,” Prof Castro Neto said.
Because they are atomically thin, two-dimensional superconducting materials would have advantages over traditional superconductors, in applications such as smaller, portable magnetic resonance imaging (MRI) machines.
One specific goal of the NUS research team is to develop high-temperature two-dimensional superconducting materials. Current materials require an extremely cold temperature of -270°C to function, ruling out exciting applications such as lossless electrical lines, levitating trains and MRI machines.
The technique, which took the researchers two years to develop, will enable new experiments that shine light on high-temperature superconductivity and other solid-state phenomena of interest. With a wide range of materials awaiting testing, electric field doping greatly widens the possibilities of solid-state science.
Original Publication: L. J. Li et al. Controlling many-body states by the electric-field effect in a two-dimensional material, Nature (2015). DOI: 10.1038/nature16175
Commentary in Nature Nanotechnology: Peter Abbamonte, 2D superconductivity: Electric tuning of many-body states, Nature Nanotechnology (2016). DOI:10.1038/nnano.2016.7
Media coverage as of December 27th
- The Strait Times, 24 Dec 2015, Page B6, Researchers find new way to control electrons
- The Straits Times Online, 24 Dec 2015, Researchers find new way to control electrons
- Channel NewsAsia Online, 24 Dec 2015, NUS scientists discover way to control electrons in thin semiconductors
- Channel 8 News Online, 24 Dec 2015, Researchers here develop new method to control electrons
- Capital Radio 95.8FM, 24 Dec 2015, Researchers here develop new method to control electrons
- Nanowerk, 24 Dec 2015, Choreographing the dance of electrons
- Phys Org, 24 Dec 2015, Choreographing the dance of electrons
- Nanotechnology Now, 24 Dec 2015, Choreographing the dance of electrons
- Health Medicine Network, 24 Dec 2015, Choreographing the dance of electrons
- AsiaOne, 25 Dec 2015, Researchers find new way to control electrons
- Iran Daily, 25 Dec 2015, Choreographing dance of electrons
- Science Newsline, 25 Dec 2015, Choreographing the dance of electrons
- Crazy Engineers, 25 Dec 2015, Scientists Discover New Way To Manage Electrons In Slim Semiconductors