Difference frequency generation in topological semimetals
When two lasers are applied to a noncentrosymmetric material, it can generate light at the difference of the incoming frequencies Δω, a phenomenon known as difference frequency generation (DFG), well characterized in semiconductors. In this work, we derive a general expression for DFG in metals, whi...
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| Format: | Article |
| Language: | English |
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American Physical Society
2020
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| Online Access: | https://hdl.handle.net/1721.1/125455 |
| _version_ | 1826200495394390016 |
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| author | Zhang, Yang |
| author2 | Massachusetts Institute of Technology. Department of Physics |
| author_facet | Massachusetts Institute of Technology. Department of Physics Zhang, Yang |
| author_sort | Zhang, Yang |
| collection | MIT |
| description | When two lasers are applied to a noncentrosymmetric material, it can generate light at the difference of the incoming frequencies Δω, a phenomenon known as difference frequency generation (DFG), well characterized in semiconductors. In this work, we derive a general expression for DFG in metals, which we use to show that the DFG in chiral topological semimetals under circular polarized light is quantized in units of e^{3}/h^{2} and independent of material parameters, including the scattering time τ, when Δω≫τ^{−1}. In this regime, DFG provides a simpler alternative to measure a quantized response in metals compared to previous proposals based on single frequency experiments. Our general derivation unmasks, in addition, a free-carrier contribution to the circular DFG beyond the semiclassical one. This contribution can be written as a Fermi surface integral, features strong frequency dependence, and oscillates with a π/2 shift with respect to the quantized contribution. We make predictions for the circular DFG of chiral and nonchiral materials using generic effective models, and ab initio calculations for TaAs and RhSi. Our work provides a complete picture of the DFG in the length gauge approach, in the clean, noninteracting limit, and highlights a plausible experiment to measure topologically quantized photocurrents in metals. |
| first_indexed | 2024-09-23T11:37:21Z |
| format | Article |
| id | mit-1721.1/125455 |
| institution | Massachusetts Institute of Technology |
| language | English |
| last_indexed | 2024-09-23T11:37:21Z |
| publishDate | 2020 |
| publisher | American Physical Society |
| record_format | dspace |
| spelling | mit-1721.1/1254552022-09-27T20:49:21Z Difference frequency generation in topological semimetals Zhang, Yang Massachusetts Institute of Technology. Department of Physics When two lasers are applied to a noncentrosymmetric material, it can generate light at the difference of the incoming frequencies Δω, a phenomenon known as difference frequency generation (DFG), well characterized in semiconductors. In this work, we derive a general expression for DFG in metals, which we use to show that the DFG in chiral topological semimetals under circular polarized light is quantized in units of e^{3}/h^{2} and independent of material parameters, including the scattering time τ, when Δω≫τ^{−1}. In this regime, DFG provides a simpler alternative to measure a quantized response in metals compared to previous proposals based on single frequency experiments. Our general derivation unmasks, in addition, a free-carrier contribution to the circular DFG beyond the semiclassical one. This contribution can be written as a Fermi surface integral, features strong frequency dependence, and oscillates with a π/2 shift with respect to the quantized contribution. We make predictions for the circular DFG of chiral and nonchiral materials using generic effective models, and ab initio calculations for TaAs and RhSi. Our work provides a complete picture of the DFG in the length gauge approach, in the clean, noninteracting limit, and highlights a plausible experiment to measure topologically quantized photocurrents in metals. 2020-05-26T18:10:19Z 2020-05-26T18:10:19Z 2020-01-15 2020-01-15T15:11:07Z Article http://purl.org/eprint/type/JournalArticle 2643-1564 https://hdl.handle.net/1721.1/125455 Juan, F. de et al. “Difference frequency generation in topological semimetals.” Physical review research 2 (2020): 012017 © 2020 The Author(s) PUBLISHER_CC PUBLISHER_CC en http://dx.doi.org/10.1103/PhysRevResearch.2.012017 Physical review research Creative Commons Attribution 4.0 International license https://creativecommons.org/licenses/by/4.0/ application/pdf American Physical Society American Physical Society |
| spellingShingle | Zhang, Yang Difference frequency generation in topological semimetals |
| title | Difference frequency generation in topological semimetals |
| title_full | Difference frequency generation in topological semimetals |
| title_fullStr | Difference frequency generation in topological semimetals |
| title_full_unstemmed | Difference frequency generation in topological semimetals |
| title_short | Difference frequency generation in topological semimetals |
| title_sort | difference frequency generation in topological semimetals |
| url | https://hdl.handle.net/1721.1/125455 |
| work_keys_str_mv | AT zhangyang differencefrequencygenerationintopologicalsemimetals |