Quantization of intra- and inter-band Berry phases in the shift current
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| Format: | Preprint |
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2022
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| _version_ | 1866910587395506176 |
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| author | Alexandradinata, A. |
| author_facet | Alexandradinata, A. |
| contents | The theory of the shift current is thus far geometrical without being topological. This means that the real-space displacement/shift of a photoexcited quasiparticle depends on the geometric Berry phase, but the Berry phase is not quantized to a rational multiple of $2π$. I rectify this status quo by introducing a new class of topological insulators whose band topology is \textit{only} compatible with a non-centrosymmetric space group. For such insulators, it is impossible to continuously tune the $\boldsymbol{k}$-dependent shift vector to zero throughout the Brillouin zone. Suitably averaged, the shift vector is quantized to a rational multiple of a Bravais lattice vector. Even with wide band gaps, the frequency-integrated shift conductivity greatly exceeds $e^3/h^2$, and is at least three orders of magnitude larger than the conductivity of the prototypical ferroelectric BaTiO$_3$. The large conductivity is attributed to an interplay between quantized intra- and inter-band Berry phases. In particular, topological defects of the inter-band Berry phase can enhance the shift current, even for unpolarized insulators with negligible intra-band Berry phase. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2203_11225 |
| institution | arXiv |
| publishDate | 2022 |
| record_format | arxiv |
| spellingShingle | Quantization of intra- and inter-band Berry phases in the shift current Alexandradinata, A. Mesoscale and Nanoscale Physics The theory of the shift current is thus far geometrical without being topological. This means that the real-space displacement/shift of a photoexcited quasiparticle depends on the geometric Berry phase, but the Berry phase is not quantized to a rational multiple of $2π$. I rectify this status quo by introducing a new class of topological insulators whose band topology is \textit{only} compatible with a non-centrosymmetric space group. For such insulators, it is impossible to continuously tune the $\boldsymbol{k}$-dependent shift vector to zero throughout the Brillouin zone. Suitably averaged, the shift vector is quantized to a rational multiple of a Bravais lattice vector. Even with wide band gaps, the frequency-integrated shift conductivity greatly exceeds $e^3/h^2$, and is at least three orders of magnitude larger than the conductivity of the prototypical ferroelectric BaTiO$_3$. The large conductivity is attributed to an interplay between quantized intra- and inter-band Berry phases. In particular, topological defects of the inter-band Berry phase can enhance the shift current, even for unpolarized insulators with negligible intra-band Berry phase. |
| title | Quantization of intra- and inter-band Berry phases in the shift current |
| topic | Mesoscale and Nanoscale Physics |
| url | https://arxiv.org/abs/2203.11225 |