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The quantum anomalous Hall (QAH) state is a two-dimensional topological insulating state that has quantized Hall resistance of h/Ce 2 and vanishing longitudinal resistance under zero magnetic field, where C is called the Chern number 1,2 . The QAH effect has been realized in magnetic topological insulators (TIs) 3-9 and magic-angle twisted bilayer graphene 10,11 . Despite considerable experimental efforts, the zero magnetic field QAH effect has so far been realized only for C = 1. Here we used molecular beam epitaxy to fabricate magnetic TI multilayers and realized the QAH effect with tunable Chern number C up to 5. The Chern number of these QAH insulators is tuned by varying the magnetic doping concentration or the thickness of the interior magnetic TI layers in the multilayer samples. A theoretical model is developed to understand our experimental observations and establish phase diagrams for QAH insulators with tunable Chern numbers. The realization of QAH insulators with high tunable Chern numbers facilitates the potential applications of dissipationless chiral edge currents in energy-

The quantum anomalous Hall (QAH) effect is a quintessential consequence of non-zero Berry curvature in momentum-space. The QAH insulator harbors dissipation-free chiral edge states in the absence of an external magnetic field. On the other hand, the topological Hall (TH) effect, a transport hallmark of the chiral spin textures, is a consequence of realspace Berry curvature. While both the QAH and TH effects have been reported separately, their coexistence, a manifestation of entangled chiral edge states and chiral spin textures, has not been reported. Here, by inserting a TI layer between two magnetic TI layers to form a sandwich heterostructure, we realized a concurrence of the TH effect and the QAH effect through electric field gating. The TH effect is probed by bulk carriers, while the QAH effect is characterized by chiral edge states. The appearance of TH effect in the QAH insulating regime is the consequence of chiral magnetic domain walls that result from the gate-induced Dzyaloshinskii-Moriya interaction and occur during the magnetization reversal process in the magnetic TI sandwich samples. The coexistence of chiral edge states and chiral spin textures potentially provides a unique platform for proof-of-concept dissipationless spintextured spintronic applications. Electronic band structures of nontrivial topology in momentum-space and magnetic chiral spin textures in real-space have attracted enormous attention in the past decade since they harbor elegant Berry curvature physics 1, 2, 3 . The intrinsic anomalous Hall (AH) effect is such an example: it is induced by the Berry curvature in momentum-space in ferromagnetic (FM) materials 4 and can even be quantized under certain circumstances, leading to the quantum anomalous Hall (QAH)effect. The QAH effect has been theoretically proposed 5, 6, 7, 8 and experimentally realized 9,10,11,12,13 in magnetically doped topological insulator (TI) films. On the other hand, chiral spin textures (e.g. skyrmions) provide another example of nontrivial topology, but in real-space. It has been shown that chiral spin textures can also induce a Hall current: this is known as the topological Hall (TH) effect and is generally regarded as the transport signature of non-zero spin chirality 3 . The TH effect has been experimentally observed in many metallic systems, such as MnSi 14, 15 , MnGe 16 , FeGe 17 , and SrIrO3/SrRuO3 interface 18,19 as well as magnetically doped TI films and heterostructures 20, 21 . The TH effect in these systems is usually observed accompanied by the AH effect. However, there is no conclusive evidence to date that the AH effect found in these metallic systems to be intrinsic, i.e., exclusively induced by the momentum-space Berry curvature 4 .The QAH and TH effects have been separately observed in magnetically doped TI 9, 10, 20, 21 , with distinctly different sample geometries. The QAH effect can be realized only in the insulating regime of a magnetic TI 9,10,11,12,13 while the TH effect is usually seen in metallic systems 20, 21 .In this Article, we re...

A quantum anomalous Hall (QAH) insulator coupled to an s-wave superconductor is predicted to harbor chiral Majorana modes. A recent experiment interprets the half-quantized two-terminal conductance plateau as evidence for these modes in a millimeter-size QAH-niobium hybrid device. However, non-Majorana mechanisms can also generate similar signatures, especially in disordered samples. Here, we studied similar hybrid devices with a well-controlled and transparent interface between the superconductor and the QAH insulator. When the devices are in the QAH state with well-aligned magnetization, the two-terminal conductance is always half-quantized. Our experiment provides a comprehensive understanding of the superconducting proximity effect observed in QAH-superconductor hybrid devices and shows that the half-quantized conductance plateau is unlikely to be induced by chiral Majorana fermions in samples with a highly transparent interface.