{"about":{"site":"https://codewithpapers.app","non_affiliation":"Code with Papers and Syntology are not affiliated with, endorsed by, or sponsored by Papers with Code, Meta, or the pwc-archive mirror.","licence":"CC BY-SA 4.0","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","attribution":"https://codewithpapers.app/attribution","modified":"archive material modified by Syntology; see the attribution page"},"url":"/paper/phonon-mean-free-path-spectroscopy-by-raman","title":"Phonon Mean Free Path Spectroscopy By Raman Thermometry","arxiv_id":"2505.14506","date":"2025-05-20","proceeding":null,"authors":["Katharina Dudde","Mahmoud Elhajhasan","Guillaume Würsch","Julian Themann","Jana Lierath","Dwaipayan Paul","Nakib H. Protik","Giuseppe Romano","Gordon Callsen"],"abstract":"In this work, we exemplify on a bulk silicon sample that Raman thermometry is capable of phonon mean free path (PMFP) spectroscopy. Our experimental approach is similar to the variation of different characteristic length scales $l_{c}$ during thermal reflectance measurements in the time or frequency domain and transient thermal grating spectroscopy. In place of $l_{c}$, we vary the laser focus spot size ($w_{e}$) and the light penetration depth ($h_{\\alpha}$) during one-laser Raman thermometry (1LRT) measurements. For our largest $w_{e}$ values, the derived effective thermal conductivities $\\kappa_{eff}$ converge towards the bulk thermal conductivity $\\kappa_{bulk}$ for silicon. However, towards smaller $w_{e}$ values, we observe a pronounced increase for the $\\kappa_{eff}$ values, which amounts up to a factor of 5.3 at 293K and even 8.3 at 200K. We mainly assign this phenomenon to quasi-ballistic phonon transport. As a result, we can compare our measured $\\kappa_{eff}(w_{e})$ trends with the thermal accumulation function $\\kappa_{cum}$ and its dependence on the phonon mean free path $l_{ph}$, which we derive from ab initio solutions of the linearized phonon Boltzmann transport equation (BTE). Since the variation of $w_{e}$ can be experimentally cumbersome, we also suggest varying $h_{\\alpha}(\\lambda)$ via the applied Raman laser wavelength $\\lambda$ during 1LRT. In this regard, we present proof-of-principle 1LRT measurements, yielding a step-like $\\kappa_{eff}(\\lambda)$ trend for four different $\\lambda$ values, which we also interpret in terms of quasi-ballistic phonon transport. Our results shall seed future PMFP spectroscopy based on 1LRT, which can directly be benchmarked against state-of-art theory by comparison of $\\kappa_{\\text{cum}}$ trends and not only $\\kappa$ values, aiming to test our understanding of the intricate phonon transport physics.","url_abs":"https://arxiv.org/abs/2505.14506v1","url_pdf":"https://arxiv.org/pdf/2505.14506v1.pdf","source":{"archive":"pwc-archive (Hugging Face), CC BY-SA 4.0","snapshot":"2025-07-28","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","row_kind":"links_only","authors_date_abstract":"arXiv metadata, CC0 1.0 (https://info.arxiv.org/help/license), from the Kaggle arXiv metadata snapshot of 2026-09-12"},"code_links":[{"paper_slug":"phonon-mean-free-path-spectroscopy-by-raman","repo_url":"https://github.com/nakib/elphbolt","is_official":0,"mentioned_in_paper":0,"mentioned_in_github":1,"framework":"tf","reach":null}],"tasks":[],"methods":[],"datasets_introduced":[],"methods_introduced":[],"results":[],"syntology":{"syntology_url":null,"atlas_url":null,"mcp":null,"developers":"https://syntology.ai/developers"},"arxiv_metadata":null,"syntology_extracted_results":null}