Observation of the Josephson effect in superhydrides: DC SQUID based on (La,Ce)H<sub>10+x</sub> with operating temperature of 179 K

<p>Among known materials, hydride superconductors have the highest critical temperatures and are very promising as a basis for electronic sensors. Superconducting quantum interference device (SQUID), due to its unique sensitivity to magnetic fields, is the most important application of superconductors in microelectronics. In this work, we describe a direct current SQUID made of lanthanum-cerium superhydride (La, Ce)H<sub>10+<i>x</i></sub> (<i>x</i> is between ‒1 and +2) at pressure of 148 GPa, with operating temperature of 179 K and bias current of about 2 mA. When placing (La, Ce)H<sub>10+x</sub> in a modulated magnetic field (frequency: 0.1-0.005 Hz, 5 Gauss), we observed generation of higher harmonics up to 18ν<sub>0</sub> and a periodic dependence of the sample resistance on the magnetic flux density <i>R</i>∝ |sin(πФ/Ф<sub>0</sub>)|. We demonstrate that the (La, Ce)H<sub>10+x</sub> SQUID with a size of ~ 4-6 μm, operates in the mode of low thermal fluctuations and can be used to detect magnetic fields below 0.1 G. Our findings pave the road to more advanced applications of the Josephson effect and SQUIDs made of hydride superconductors.</p>