Imaging the Meissner effect in pressurized bilayer nickelate with integrated multi-parameter quantum sensor
Junyan Wen, Yue Xu, Gang Wang, Zhi He, Yang Chen, Ningning Wang, Tenglong Lu, Xiaoli Ma, Feng Jin, Liu-Cheng Chen, Miao Liu, Jing-Wei Fan, Xiaobing Liu, Xu Pan, Gang‐Qin Liu, Jinguang Cheng, Xiaohui Yu
Abstract
ABSTRACT Recent reports on the signatures of high-temperature superconductivity with a critical temperature (Tc) close to 80 K have triggered great research interest and extensive follow-up studies. Although zero resistance has been successfully achieved under improved hydrostatic pressure conditions, the Meissner effect of La3Ni2O7–δ under high pressure remains controversial. Here, using shallow nitrogen-vacancy centers implanted on the culet of diamond anvils as in situ quantum sensors, we observe compelling evidence for the Meissner effect in polycrystalline bilayer nickelate samples: magnetic field expulsion during both field-cooling and field-warming processes. In particular, we explore the multi-parameter measurement capacity of the diamond quantum sensors to extract the weak demagnetization signal of La3Ni2O7–δ. The correlated measurements of Raman spectra and magnetic imaging indicate an incomplete structural transformation related to the displacement of oxygen ions emerging in the non-superconducting region. Our work clarifies the controversy about the Meissner effect of La3Ni2O7–δ and contributes to the development of quantum sensing of weak signals under high-pressure conditions.