Pressure-induced anomalous insulating behavior in frustrated iridate La 3 Ir 3 O 11

• Published in: Chinese physics B 2021-06, Vol.30 (6), p.67402
• Main Authors: Chen, Chun-Hua, Zhou, Yong-Hui, Zhou, Ying, Yuan, Yi-Fang, An, Chao, Chen, Xu-Liang, Tian, Zhao-Ming, Yang, Zhao-Rong
• Format: Article
• Language: English
• ISSN: 1674-1056
• DOI: 10.1088/1674-1056/abf100

The geometrically frustrated iridate La 3 Ir 3 O 11 with strong spin–orbit coupling and fractional valence was recently predicted to be a quantum spin liquid candidate at ambient conditions. Here, we systematically investigate the evolution of structural and electronic properties of La 3 Ir 3 O 11 under high pressure. Electrical transport measurements reveal an abnormal insulating behavior rather than metallization above a critical pressure P c ∼ 38.7 GPa. Synchrotron x-ray diffraction (XRD) experiments indicate the stability of the pristine cubic KSbO 3 -type structure up to 73.1 GPa. Nevertheless, when the pressure gradually increases across P c , the bulk modulus gets enhanced and the pressure dependence of bond length d Ir – Ir undergoes a slope change. Consistent with the XRD data, detailed analyses of Raman spectra reveal an abnormal redshift of Raman mode and a change of Raman intensity around P c . Our results demonstrate that the pressure-induced insulating behavior in La 3 Ir 3 O 11 can be assigned to the structural modification, such as the distortion of IrO 6 octahedra. These findings will shed light on the emergent abnormal insulating behavior in other 5d iridates reported recently.