Nonreciprocal perfect Coulomb drag in electron-hole bilayers: coherent exciton superflow as a diode
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arXiv
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| Format: | Preprint |
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2026
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| _version_ | 1866918320506142720 |
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| author | Hui, Jun-Xiao Jiang, Qing-Dong |
| author_facet | Hui, Jun-Xiao Jiang, Qing-Dong |
| contents | Distinguishing an exciton condensate from an excitonic gas or insulator remains a fundamental challenge, as both phases feature bound electron-hole pairs but differ only by the emergence of macroscopic phase coherence. Here, we theoretically propose that a spin-orbit-coupled bilayer system can host a finite-momentum exciton condensate exhibiting a nonreciprocal perfect Coulomb drag -- the coherent-exciton diode effect. This effect arises from the simultaneous breaking of inversion and time-reversal symmetries in the exciton condensate, resulting in direction-dependent critical counterflow currents. The resulting nonreciprocal perfect Coulomb drag provides a clear and unambiguous transport signature of phase-coherent exciton condensation, offering a powerful and experimentally accessible approach to identify, probe, and control exciton superfluidity in solid-state platforms. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2602_02643 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Nonreciprocal perfect Coulomb drag in electron-hole bilayers: coherent exciton superflow as a diode Hui, Jun-Xiao Jiang, Qing-Dong Mesoscale and Nanoscale Physics Strongly Correlated Electrons Distinguishing an exciton condensate from an excitonic gas or insulator remains a fundamental challenge, as both phases feature bound electron-hole pairs but differ only by the emergence of macroscopic phase coherence. Here, we theoretically propose that a spin-orbit-coupled bilayer system can host a finite-momentum exciton condensate exhibiting a nonreciprocal perfect Coulomb drag -- the coherent-exciton diode effect. This effect arises from the simultaneous breaking of inversion and time-reversal symmetries in the exciton condensate, resulting in direction-dependent critical counterflow currents. The resulting nonreciprocal perfect Coulomb drag provides a clear and unambiguous transport signature of phase-coherent exciton condensation, offering a powerful and experimentally accessible approach to identify, probe, and control exciton superfluidity in solid-state platforms. |
| title | Nonreciprocal perfect Coulomb drag in electron-hole bilayers: coherent exciton superflow as a diode |
| topic | Mesoscale and Nanoscale Physics Strongly Correlated Electrons |
| url | https://arxiv.org/abs/2602.02643 |