Quantum Materials - 04

Abstract

Recently, La₃Ni₂O₇ was reported to show superconductivity under pressure of 14 GPa, with transition temperature(T_c) of 80 K[1]. La₃Ni₂O₇ is a bilayer Ruddlesden-Popper phase nickelate that has two layers of NiO₂ plane in its unit cell, while there also exists trilayer family compound: La₄Ni₃O₁₀. As there had been no studies yet that reports superconductivity in La₄Ni₃O₁₀, we investigated the possibility of superconductivity in this compound under high pressure [2].
The polycrystalline La₄Ni₃O_10+δ samples were synthesized via solid-state reaction and hot isostatic pressing process, and characterized by powder X-ray diffraction and thermogravimetric analysis to find it to be single phase La₄Ni₃O_10.04 and La₄Ni₃O_9.99. We used diamond anvil cell with boron-doped diamond electrodes designed for four-terminal resistance measurement under high pressure [3].
The temperature dependence of the resistance of La₄Ni₃O_10.04 and La₄Ni₃O_9.99 under various pressures are shown in Fig.1 [4]. In the case of La₄Ni₃O_10.04, the resistance exhibits a slight suppression below 5 K at 20.2 GPa, with this suppression becoming more pronounced under higher pressures. The suppression is most likely attributable to the onset of superconductivity because it was suppressed by magnetic field. For La₄Ni₃O_10.04, T_c rapidly increases with increasing pressure from 20.2 GPa, reaches at 36 K at 48.0 GPa, and then gradually decreases with further pressure increase. In contrast, for La₄Ni₃O_9.99, superconductivity begins to appear at 32.8 GPa and T_c gradually increases with increasing pressure. Thus, T_c of La₄Ni₃O_10+δ exhibits a strong dependence on oxygen-content within the pressure range of approximately 20 to 80 GPa.