Apply a little voltage and this superconductor turns into an insulator

Hong Hengfei, Zhou Wei, reporter, Jiang Yun, China.
Photo courtesy of China.
Lanthanum aluminate and potassium tantalate are originally two insulators, but when combined, the interface can conduct electricity or even superconductivity.
It was officially published in Science magazine in February this year.
The discovery of "Appearance" aroused the interest of scientists to continue to explore secrets
.
Recently, researcher Xie Yanwu from the Department of Physics of Zhejiang University, in collaboration with researchers Sun Jirong and Zhou Yi from the Institute of Physics of the Chinese Academy of Sciences, found that the gate voltage can be used to continuously control the conductivity of the lanthanum aluminate/potassium tantalate interface like a semiconductor device: As the voltage changes, the interface presents a continuous transition from superconducting to insulator
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At the same time, the research team also observed many novel physical phenomena such as quantum metal states that can be continuously regulated at the interface
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Related papers will be online in the journal Science on May 14
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????Controlling the distribution of electrons? Transforming the superconducting properties of the oxide interface In 2007, Professor Triscone of the University of Geneva, Switzerland, first discovered the existence of superconductivity at the lanthanum aluminate/strontium titanate interface
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This marked the birth of a new type of superconducting system: oxide interface superconductivity
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"Subsequent research has found that the superconductivity of the lanthanum aluminate/strontium titanate interface can be turned on or off by voltage, just like a semiconductor transistor
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" Xie Yanwu said, this is imaginative, and perhaps one day the academic world can produce something like a semiconductor.
The same superconducting device that can be precisely regulated
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In this study, the research team discovered a new regulation mechanism that realized the continuous adjustment of the conductivity of lanthanum aluminate/potassium tantalate, and the device showed a continuous transition from superconductivity to insulator with voltage changes
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Xie Yanwu introduced that conducting electrons paired up at low temperatures to form superconductivity.
There are already many known superconducting systems, but there are very few superconducting systems that can be controlled by electric fields
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"The essence of our control method is to control the spatial distribution of electronic'formations' so that they move closer or farther away from the interface. .
When a large number of electrons move near the oxide interface, they will be affected by lattice defects (also known as "disorder"), just like when you encounter obstacles when driving
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The closer this "disorder" is to the interface, the denser the distribution.
The farther away from the interface, the sparser
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Based on this understanding, the research team proposed an idea to change the spatial distribution of electrons
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"If there are more electrons close to the interface, then as a whole, they will encounter more'obstacles' , This will significantly affect the motion behavior of the electrons and the superconducting Cooper pair after pairing
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"Found new clues? Observed novel quantum metal states.
Xie Yanwu said that the research momentum for new materials mainly comes from two aspects: on the one hand, they want to discover new physical phenomena and gain more scientific insights through the research of new materials; on the other hand, they want to discover new physical phenomena through the research of new materials; On the one hand, they are also trying to provide useful clues for the development of new devices
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In this experiment, the researchers tested the conductivity of the interface when the gate voltage ranges from -200 volts to 150 volts
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The first author of the paper, Department of Physics, Zhejiang University Dr.
Chen Zheng said: "We directly measured the changes in the spatial distribution of the electron'formation' in this gate voltage range.
When the conductive channel is 6 nanometers, lanthanum aluminate/potassium tantalate seems to be a good superconductor.
When the channel is adjusted to 2 nanometers, it becomes an insulator
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As the experiment progressed, more and more data emerged-no matter how the temperature changes in the range of 0 to 1 Kelvin, the resistance of the lanthanum aluminate/potassium tantalate interface is almost always constant
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"Quantum metals are A novel quantum state of matter with partial superconductivity and metallic properties at the same time, which is a typical quantum metallic state
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"Zhou Yi said that the known quantum metal states are only at a certain quantum critical point
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This system can be continuously controlled, and the quantum metal exists as a phase in the phase diagram
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The reviewer of "Science" magazine is right.
This research gave a very positive response
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They believe that this fully tunable superconductivity is a fascinating breakthrough.
The research is fully in-depth and almost covers people’s work in lanthanum aluminate/tantalic acid in the past ten years.
Knowledge gained in the potassium system
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Xie Yanwu said: "Our research in the lanthanum aluminate/potassium tantalate system can provide new materials for understanding the mechanism of superconductivity, especially the mechanism in high-temperature superconductivity, and present a new perspective for people to explore low-temperature quantum phenomena.
It also provides new ideas for the research and development of superconducting devices
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"