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Superconductivity in compressed lithium at 20 K

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Abstract

Superconductivity at high temperatures is expected in elements with low atomic numbers, based in part on conventional BCS (Bardeen–Cooper–Schrieffer) theory1. For example, it has been predicted that when hydrogen is compressed to its dense metallic phase (at pressures exceeding 400 GPa), it will become superconducting with a transition temperature above room temperature2. Such pressures are difficult to produce in a laboratory setting, so the predictions are not easily confirmed. Under normal conditions lithium is the lightest metal of all the elements, and may become superconducting at lower pressures3,4; a tentative observation of a superconducting transition in Li has been previously reported5. Here we show that Li becomes superconducting at pressures greater than 30 GPa, with a pressure-dependent transition temperature (Tc) of 20 K at 48 GPa. This is the highest observed Tc of any element; it confirms the expectation that elements with low atomic numbers will have high transition temperatures, and suggests that metallic hydrogen will have a very high Tc. Our results confirm that the earlier tentative claim5 of superconductivity in Li was correct.

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References

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Acknowledgements

We thank H. Goto for technical support in machining the pit-anvils. This work was supported by a Grant-in-Aid for COE (Center of Excellence) Research and Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan.

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Competing interests

The authors declare that they have no competing financial interests.

Correspondence to Katsuya Shimizu.

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Further reading

Figure 1: Arrangement of sample and electrodes on the diamond anvils.
Figure 2: Temperature dependence of the electrical resistance of lithium measured at temperatures below 50 K.
Figure 3: The effect of magnetic fields on the behaviour of the resistance drop in run no. 3.
Figure 4: Pressure dependence of the superconducting onset temperature, Tc onset, for Li.

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