Molecular beam epitaxy (MBE) is an epitaxial process by which we could grow single-crystal thin films, heterostructures, and superlattices with the highest achievable purity. Therefore, MBE is known as one of the most advanced and controllable material synthesis methods. In this talk, I will briefly introduce the MBE growth mechanism and then focus on my research, which centers on the MBE growth of quantum materials, spanning from topological materials to interfacial superconductors, and the pursuit of the new phenomena therein for quantum information science. I will talk about the only two solid-state phenomena with zero-resistance: the quantum anomalous Hall (QAH) effect and the interface superconductivity. The QAH insulator is a material in which the interior is insulating but electrons can travel with zero resistance along one-dimensional conducting edge channels. Owing to its resistance-free edge channels, the QAH insulator is an outstanding platform for energy efficient electronics and spintronics as well as topological quantum computations. With many efforts, we were the first to realize the QAH effect in MBE-grown Cr- and V-doped TI thin films [1,2]. I will briefly talk about the route to the QAH effect and then focus on our recent progress on the new quantum phenomenon in MBE-grown magnetic TI multilayers, including the axion insulator [3], the QAH insulator with multiple edge channels [4], and the absence of Majorana physics in millimeter-size QAH/superconductor heterostructures [5]. Finally, I will talk about the interfacial superconductivity in MBE-grown TI/iron chalcogenide heterostructures. Moreover, the TI/iron chalcogenide heterostructures fulfills the two essential ingredients of topological superconductivity, i.e. topological and superconducting orders, and thus provide an alternative platform for the exploration of Majorana physics towards the scale topological quantum computations.

References 

 [1] Chang et al, Science 340, 167(2013).

 [2] Chang et al, Nature Mater. 14, 473(2015)

 [3] Xiao et al, Phys. Rev. Lett. 120, 056801 (2018)

 [4] Zhao et al, Nature 588, 419 (2020).

 [5] Kayyalha et al, Science 367, 64(2020)