A team of physicist from the University of Groningen lead by professor Justin Ye has constructed a superconducting transistor that operates at a few Kelvin. The back gate, which switches the molybdenum disulfide transistor from the metallic to the superconducting phase operates continuously at low voltage. A transistor like this could be used in quantum logic circuits. The results were published on May 28th, 2018 in the journal Advanced Materials.
Switching the properties of quantum electronic systems, like the superconducting phase, is quite challenging. Superconducting transistor-like devices have been constructed, but these prototypes still have major drawbacks, explains University of Groningen associate professor of Quantum Interfaces and Device Physics Justin Ye. ‘Most of these systems can perform continuous switching, as they need to be cooled down or warmed up to do this. Furthermore, for exceptions that can be tuned contnously, a high voltage is needed to switch between states, as well as temperatures below 1.5 Kelvin.’ Cooling below this temperature requires complex equipment and the very rare Helium-3.
By contrast, Ye now presents a dual gate device in which he can switch between metallic and superconducting phase with a low voltage back gate for 20 Volts at ~10 Kelvin. The device, based on molybdenum disulfide, operates like a field effect transistor. Ye uses an ionic liquid gate to add charge carriers to the material. This is tuned to the tipping point between the metallic and superconducting phase, so a back gate of hafnium oxide operating below 20 volt can switch the device between states.
‘As far as I know, we are the first to make a superconducting transistor with continuous switching at temperatures at a easily accessible temperature of a few Kelvin’, says Ye. The latter means that his transistor operates in a relatively simple cooling device using Helium-4. Ye’s group first showed that molybdenum disulfide – a semiconductor, but also a common dry lubricant – became a superconductor at low temperatures in 2012. ‘We used the same type of device in this new experiment, but we improved the dielectric properties of the back gate, to obtain a bigger range of tuning carriers.’
This process took several years, but the result is quite rewarding. ‘We can now switch a quantum state. Eventually, this could lead to the construction of superconducting logic circuits.’ But although the current device shows all the function of a real transistor, such an application is still a long way off. ‘The next step is to show the frequency response’, says Ye. However, building applications is one of the aims of his group. ‘We are into scientific exploration; we make devices with the aim to find both new physical phenomena and new functionaliites.’
Continuous Low‐Bias Switching of Superconductivity in a MoS2Transistor Qihong Chen, Jianming Lu, Lei Liang, Oleksandr Zheliuk, Abdurrahman Ali El Yumin & Jianting Ye, Advanced Materials, Early Online Version (28 May 2018)
For more information please contact Prof. Justin Ye
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