Thermoelectric properties of magic angle twisted bilayer graphene-superconductor hetero-junction: effect of valley polarization and trigonal warping
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arXiv
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| Autores principales: | , , , |
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| Formato: | Preprint |
| Publicado: |
2025
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| _version_ | 1866911203189587968 |
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| author | Bera, Kamalesh Chatterjee, Pritam Mohan, Priyanka Saha, Arijit |
| author_facet | Bera, Kamalesh Chatterjee, Pritam Mohan, Priyanka Saha, Arijit |
| contents | We theoretically investigate the thermoelectric properties (electronic contribution) of a normal-superconductor (NS) hybrid junction, where the normal region consists of magic-angle twisted bilayer graphene (MATBG). The superconducting region is characterized by a common $s$-wave superconductor closely proximitized to the MATBG. We compute various thermoelectric coefficients, including thermal conductance, thermopower, and the figure of merit ($zT$), using the scattering matrix formalism. These results are further supported by calculations based on a lattice-regularized version of the effective Hamiltonian. Additionally, we explore the impact of trigonal warping and valley polarization on the thermoelectric coefficients. Notably, we find a significant variation in $zT$ as a function of these parameters, reaching values as high as 2.5. Interestingly, we observe a violation of the Wiedemann-Franz law near the charge neutrality point with the superconducting correlation, indicating that MATBG electrons behave as slow Dirac fermions in this regime. This observation is further confirmed by the damped oscillatory behavior of the thermal conductance as a function of the barrier strength when an insulating barrier is modelled at the interface of the NS junction. Beyond theoretical insights, our findings suggest new possibilities for thermoelectric applications using MATBG based NS junctions. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2501_15882 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Thermoelectric properties of magic angle twisted bilayer graphene-superconductor hetero-junction: effect of valley polarization and trigonal warping Bera, Kamalesh Chatterjee, Pritam Mohan, Priyanka Saha, Arijit Mesoscale and Nanoscale Physics Superconductivity We theoretically investigate the thermoelectric properties (electronic contribution) of a normal-superconductor (NS) hybrid junction, where the normal region consists of magic-angle twisted bilayer graphene (MATBG). The superconducting region is characterized by a common $s$-wave superconductor closely proximitized to the MATBG. We compute various thermoelectric coefficients, including thermal conductance, thermopower, and the figure of merit ($zT$), using the scattering matrix formalism. These results are further supported by calculations based on a lattice-regularized version of the effective Hamiltonian. Additionally, we explore the impact of trigonal warping and valley polarization on the thermoelectric coefficients. Notably, we find a significant variation in $zT$ as a function of these parameters, reaching values as high as 2.5. Interestingly, we observe a violation of the Wiedemann-Franz law near the charge neutrality point with the superconducting correlation, indicating that MATBG electrons behave as slow Dirac fermions in this regime. This observation is further confirmed by the damped oscillatory behavior of the thermal conductance as a function of the barrier strength when an insulating barrier is modelled at the interface of the NS junction. Beyond theoretical insights, our findings suggest new possibilities for thermoelectric applications using MATBG based NS junctions. |
| title | Thermoelectric properties of magic angle twisted bilayer graphene-superconductor hetero-junction: effect of valley polarization and trigonal warping |
| topic | Mesoscale and Nanoscale Physics Superconductivity |
| url | https://arxiv.org/abs/2501.15882 |