After the braking of the record for the superconducting critical temperature Tc by more than 30 K, reaching 203 K for hydrogen sulfide H2S under a high pressure of 150 GPa which was the first increase in 20 years [1], several theoretical groups proposed the crystal structures and the value of Tc in a lot of hydrides. However, only a few experimental works on the investigation of the way of synthesis and the transport properties of the predicted hydrides have been reported so far.
Most recently, the direct synthesis of several hydrides, for instance, H3S and LaHx (x~10) from the mixture of the elemental sulfur and lanthanum, respectively, and H2 has been reported from several groups [2-5]. Especially, lanthanum hydride shows the highest-Tc ~ 250 K with zero electrical resistance at 170 GPa [5].
Here we report our recent results of synchrotron x-ray diffraction with electrical resistance measurements to search for superconductivity of lanthanum hydrides synthesized under high pressure and temperature.
References:
[1] A. P. Drozdov, M. I. Eremets, I. A. Troyan, V. Ksenofontov and S. I. Shylin, Nature 525, 73-76 (2015).
[2] A. F. Goncharov, S. S. Lobanov, V. B. Prakapenka, and E. Greenberg, Phys. Rev. B, 95, 140101 (2017).
[3] A. Marizy, B. Guigue, F. Occelli, B. Leridon, and P. Loubeyre, High Pressure Res., 37, 465-474 (2017)
[4] M. Somayazulu, M. Ahart, A. K. Mishra, Z. M. Geballe, M. Baldini, Y. Meng, V. V. Struzhkin, and R. J. Hemley, Phys. Rev. Lett. 122, 027001(2019).
[5] A. P. Drozdov, P. P. Kong, V. S. Minkov, S. P. Besedin, M. A. Kuzovnikov, S. Mozaffari, L. Balicas, F. F. Balakirev, D. E. Graf, V. B. Prakapenka, E. Greenberg, D. A. Knyazev, M. Tkacz and M. I. Eremets, Nature, 569, 528–531 (2019).