Xu Da, Zhong Qing, Cao Wen-Hui, Wang Xue-Shen, Wang Shi-Jian, Li Jin-Jin, Liu Jian-She, Chen Wei. A second-order gradiometric superconducting quantum interference device current sensor with cross-coupled structureJ. Acta Physica Sinica, 2021, 70(12): 128501. DOI: 10.7498/aps.70.20201816