Observation of Zero-Energy Modes with Possible Time-Reversal Symmetry Breaking on Step Edge of CaKFe4As4

Lu Cao; Geng Li; Wenyao Liu; Ya Bin Liu; Hui Chen; Yuqing Xing; Lingyuan Kong; Fazhi Yang; Quanxin Hu; Meng Li; Xingtai Zhou; Zichao Chen; Chenhang Ke; Lunhui Hu; Guang Han Cao; Congjun Wu; Hong Ding; Hong Jun Gao

doi:10.1088/0256-307X/41/11/117401

Observation of Zero-Energy Modes with Possible Time-Reversal Symmetry Breaking on Step Edge of CaKFe₄As₄

Lu Cao, Geng Li, Wenyao Liu, Ya Bin Liu, Hui Chen, Yuqing Xing, Lingyuan Kong, Fazhi Yang, Quanxin Hu, Meng Li, Xingtai Zhou, Zichao Chen, Chenhang Ke, Lunhui Hu, Guang Han Cao, Congjun Wu, Hong Ding, Hong Jun Gao

Quantum Heterostructures

Research output: Contribution to journal › Article › peer-review

Abstract

Topologically nontrivial Fe-based superconductors attract extensive attentions due to their ability of hosting Majorana zero modes (MZMs) which could be used for topological quantum computation. Topological defects such as vortex lines are required to generate MZMs. Here, we observe the robust edge states along the surface steps of CaKFe₄As₄. Remarkably, the tunneling spectra show a sharp zero-bias peak (ZBP) with multiple integer-quantized states at the step edge under zero magnetic field. We propose that the increasing hole doping around step edges may drive the local superconductivity into a state with possible spontaneous time-reversal symmetry breaking. Consequently, the ZBP can be interpreted as an MZM in an effective vortex in the superconducting topological surface state by proximity to the center of a tri-junction with different superconducting order parameters. Our results provide new insights into the interplay between topology and unconventional superconductivity, and pave a new path to generate MZMs without magnetic field.

Original language	English
Article number	117401
Journal	Chinese Physics Letters
Volume	41
Issue number	11
DOIs	https://doi.org/10.1088/0256-307X/41/11/117401
State	Published - Oct 1 2024

Funding

We thank Vadim Grinenko and Kun Jiang for help discussions. This work was supported by the National Key Research and Development Program of China (Grant No. 2019YFA0308500), the National Natural Science Foundation of China (Grant Nos. 62488201, 52072401, 11888101, 12234016, and 12174317), the Chinese Academy of Sciences (Grant No. YSBR-003), the Innovation Program of Quantum Science and Technology (Grant No. 2021ZD0302700), the New Cornerstone Science Foundation, the China Postdoctoral Science Foundation (Grant No. 2022M723111), and the Fellowship of China National Postdoctoral Program for Innovative Talents (Grant No. BX20230358).

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Cao, L., Li, G., Liu, W., Liu, Y. B., Chen, H., Xing, Y., Kong, L., Yang, F., Hu, Q., Li, M., Zhou, X., Chen, Z., Ke, C., Hu, L., Cao, G. H., Wu, C., Ding, H., & Gao, H. J. (2024). Observation of Zero-Energy Modes with Possible Time-Reversal Symmetry Breaking on Step Edge of CaKFe₄As₄. Chinese Physics Letters, 41(11), Article 117401. https://doi.org/10.1088/0256-307X/41/11/117401

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title = "Observation of Zero-Energy Modes with Possible Time-Reversal Symmetry Breaking on Step Edge of CaKFe4As4",

abstract = "Topologically nontrivial Fe-based superconductors attract extensive attentions due to their ability of hosting Majorana zero modes (MZMs) which could be used for topological quantum computation. Topological defects such as vortex lines are required to generate MZMs. Here, we observe the robust edge states along the surface steps of CaKFe4As4. Remarkably, the tunneling spectra show a sharp zero-bias peak (ZBP) with multiple integer-quantized states at the step edge under zero magnetic field. We propose that the increasing hole doping around step edges may drive the local superconductivity into a state with possible spontaneous time-reversal symmetry breaking. Consequently, the ZBP can be interpreted as an MZM in an effective vortex in the superconducting topological surface state by proximity to the center of a tri-junction with different superconducting order parameters. Our results provide new insights into the interplay between topology and unconventional superconductivity, and pave a new path to generate MZMs without magnetic field.",

author = "Lu Cao and Geng Li and Wenyao Liu and Liu, {Ya Bin} and Hui Chen and Yuqing Xing and Lingyuan Kong and Fazhi Yang and Quanxin Hu and Meng Li and Xingtai Zhou and Zichao Chen and Chenhang Ke and Lunhui Hu and Cao, {Guang Han} and Congjun Wu and Hong Ding and Gao, {Hong Jun}",

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AU - Cao, Lu

AU - Li, Geng

AU - Liu, Wenyao

AU - Liu, Ya Bin

AU - Chen, Hui

AU - Xing, Yuqing

AU - Kong, Lingyuan

AU - Yang, Fazhi

AU - Hu, Quanxin

AU - Li, Meng

AU - Zhou, Xingtai

AU - Chen, Zichao

AU - Ke, Chenhang

AU - Hu, Lunhui

AU - Cao, Guang Han

AU - Wu, Congjun

AU - Ding, Hong

AU - Gao, Hong Jun

PY - 2024/10/1

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N2 - Topologically nontrivial Fe-based superconductors attract extensive attentions due to their ability of hosting Majorana zero modes (MZMs) which could be used for topological quantum computation. Topological defects such as vortex lines are required to generate MZMs. Here, we observe the robust edge states along the surface steps of CaKFe4As4. Remarkably, the tunneling spectra show a sharp zero-bias peak (ZBP) with multiple integer-quantized states at the step edge under zero magnetic field. We propose that the increasing hole doping around step edges may drive the local superconductivity into a state with possible spontaneous time-reversal symmetry breaking. Consequently, the ZBP can be interpreted as an MZM in an effective vortex in the superconducting topological surface state by proximity to the center of a tri-junction with different superconducting order parameters. Our results provide new insights into the interplay between topology and unconventional superconductivity, and pave a new path to generate MZMs without magnetic field.

AB - Topologically nontrivial Fe-based superconductors attract extensive attentions due to their ability of hosting Majorana zero modes (MZMs) which could be used for topological quantum computation. Topological defects such as vortex lines are required to generate MZMs. Here, we observe the robust edge states along the surface steps of CaKFe4As4. Remarkably, the tunneling spectra show a sharp zero-bias peak (ZBP) with multiple integer-quantized states at the step edge under zero magnetic field. We propose that the increasing hole doping around step edges may drive the local superconductivity into a state with possible spontaneous time-reversal symmetry breaking. Consequently, the ZBP can be interpreted as an MZM in an effective vortex in the superconducting topological surface state by proximity to the center of a tri-junction with different superconducting order parameters. Our results provide new insights into the interplay between topology and unconventional superconductivity, and pave a new path to generate MZMs without magnetic field.

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Observation of Zero-Energy Modes with Possible Time-Reversal Symmetry Breaking on Step Edge of CaKFe₄As₄

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