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| Main Authors: | , , , |
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| Format: | Preprint |
| Published: |
2026
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2605.02095 |
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| _version_ | 1866911643074560000 |
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| author | Chakraborty, Subhadeep Mukhopadhyay, Aabir Khanna, Udit Das, Sourin |
| author_facet | Chakraborty, Subhadeep Mukhopadhyay, Aabir Khanna, Udit Das, Sourin |
| contents | We uncover hierarchy of topological phases within the synthetic Brillouin zone of a three-terminal Josephson junction's (3-TJJ's) Bogoliubov-de Gennes spectrum. We demonstrate that the above-gap continuum realizes a Chern insulator phase with quantized monopole charges (\pm 1), while the subgap Andreev bound states (ABS) are characterized by a quantized dipolar invariant. By breaking time-reversal symmetry at the junction, we induce synthetic flat bands that suppress DC Josephson currents across the entire phase-bias space. Furthermore, under voltage bias, the junction exhibits a robust quantization of the time-averaged transconductance that is reminiscent of a quantized Hall conductance plateau owing to the flat band limit and its dipole phase. As a byproduct, the flat band produces a global "sweet plateau" of phase insensitivity, surpassing localized sweet spots of conventional superconducting qubits and enabling a robust architecture for symmetry-protected Andreev qubits. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_02095 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Synthetic Flat Bands, Hierarchical Topology, and Phase-Fluctuation-Insensitive Quantized Transconductance in Josephson Junctions Chakraborty, Subhadeep Mukhopadhyay, Aabir Khanna, Udit Das, Sourin Mesoscale and Nanoscale Physics We uncover hierarchy of topological phases within the synthetic Brillouin zone of a three-terminal Josephson junction's (3-TJJ's) Bogoliubov-de Gennes spectrum. We demonstrate that the above-gap continuum realizes a Chern insulator phase with quantized monopole charges (\pm 1), while the subgap Andreev bound states (ABS) are characterized by a quantized dipolar invariant. By breaking time-reversal symmetry at the junction, we induce synthetic flat bands that suppress DC Josephson currents across the entire phase-bias space. Furthermore, under voltage bias, the junction exhibits a robust quantization of the time-averaged transconductance that is reminiscent of a quantized Hall conductance plateau owing to the flat band limit and its dipole phase. As a byproduct, the flat band produces a global "sweet plateau" of phase insensitivity, surpassing localized sweet spots of conventional superconducting qubits and enabling a robust architecture for symmetry-protected Andreev qubits. |
| title | Synthetic Flat Bands, Hierarchical Topology, and Phase-Fluctuation-Insensitive Quantized Transconductance in Josephson Junctions |
| topic | Mesoscale and Nanoscale Physics |
| url | https://arxiv.org/abs/2605.02095 |