Project Summary: Heterogeneous interfaces that juxtapose different materials have been known to create emergent quantum phenomena. We used molecular beam epitaxy to synthesize heterostructures formed by stacking together two magnetic materials, a ferromagnetic topological insulator (Cr,Bi,Sb)2Te3) and an antiferromagnetic metal, iron chalcogenide (FeTe). High-resolution transmission electron microscopy (HRTEM) and x-ray diffraction show the formation of heterostructures with sharp interfaces and good crystallinity. Neither of these materials is a superconductor in the native crystalline form. Yet, we observed emergent interface-induced superconductivity in these heterostructures, Using a combination of angle resolved photoemission spectroscopy (ARPES), electrical transport, reflection magnetic circular dichroism (RMCD), magnetic force microscopy, scanning tunneling microscopy, and muon spin relaxation, we demonstrated the coexistence of topological band structure, superconductivity, and ferromagnetism in the magnetic topological insulator layer. Thus, these new hybrid magnetic/topological/superconducting heterostructures provide the three essential ingredients needed for ‘chiral topological superconductivity’ and are an attractive wafer-scale platform for the exploration of a viable route toward Majorana physics.
Publication: Hemian Yi et al., Science (2024), 383, 64
2DCC Role: 2DCC facility was partially used for epitaxial growth of high-quality FeTe/(Bi,Sb,Cr)2Te3 heterostructures and their characterization using in vacuo ARPES. This project primarily involved personnel from the Penn State MRSEC and collaborators at Rutgers, Univ. Washington, and NIST.
What Has Been Achieved: This work provided the first demonstration of coexisting superconductivity, topological Dirac states, and ferromagnetic order in a single material.
Importance of the Achievement: the realization of a single epitaxial material system that combines topological states, superconductivity, and magnetism provides a possible route toward a scalable wafer-based platform that can support chiral Majorana modes that could be used in topological quantum computation schemes.
Unique Feature(s) of the MIP that Enabled this Achievement: Synthesis of high-quality FeTe/Cr-doped (Bi,Sb)2Te3 heterostructures by MBE and their in vacuo characterization by angle resolved photoemission spectroscopy.
(If Applicable) Publication: Hemian Yi, Yi-Fan Zhao, Ying-Ting Chan, Jiaqi Cai, Ruobing Mei, Xianxin Wu, Zi-Jie Yan, Ling-Jie Zhou, Ruoxi Zhang, Zihao Wang, Stephen Paolini, Run Xiao, Ke Wang, Anthony R. Richardella, John Singleton, Laurel E. Winter, Thomas Prokscha, Zaher Salman, Andreas Suter, Purnima P. Balakrishnan, Alexander J. Grutter, Moses H. W. Chan, Nitin Samarth, Xiaodong Xu, Weida Wu, Chao-Xing Liu, Cui-Zu Chang, Science (2024), 383, 64.
Acknowledgments: This work was primarily supported by US Department of Energy (DOE) grant DE-SC0023113, including the MBE growth, ARPES, and electrical transport measurements. The sample characterization was partially supported by an NSF-CAREER award (DMR-1847811) and the Penn State MRSEC for Nanoscale Science (DMR-2011839). The MBE growth and the ARPES measurements were partially performed in the NSF-supported 2DCC MIP facility (DMR-2039351). The STM/S measurements were partially supported by an Army Research Office grant (W911NF2210159). The theoretical calculations were partially supported by an NSF grant (DMR-2241327) and Penn State MRSEC for Nanoscale Science (DMR-2011839). The MFM measurements were supported by DOE grant DE-SC0018153. The RMCD measurements were supported by an Air Force Office of Scientific Research grant (FA9550-21-1-0177). Work done at the National High Magnetic Field Laboratory was supported by the NSF (DMR-1644779 and DMR-2128556) and the State of Florida. C.-Z.C. acknowledges support from the Gordon and Betty Moore Foundation’s EPiQS Initiative (grant GBMF9063 to C.-Z.C.). Certain commercial equipment, instruments, software, or materials are identified in this paper to specify the experimental procedure adequately. Such identifications are not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor are they intended to imply that the materials or equipment identified are necessarily the best available for the purpose.