{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,1]],"date-time":"2026-09-01T13:00:43Z","timestamp":1788267643017,"version":"build-2803163510"},"reference-count":42,"publisher":"MDPI AG","issue":"15","license":[{"start":{"date-parts":[[2026,8,6]],"date-time":"2026-08-06T00:00:00Z","timestamp":1785974400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["52302176"],"award-info":[{"award-number":["52302176"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"award":["52302176"],"award-info":[{"award-number":["52302176"]}],"id":[{"id":"https:\/\/ror.org\/01h0zpd94","id-type":"ROR","asserted-by":"publisher"}]},{"name":"the Hunan Provincial Natural Science Foundation of China","award":["2025JJ40049"],"award-info":[{"award-number":["2025JJ40049"]}]},{"name":"the Hunan Provincial Natural Science Foundation of China","award":["2023JJ40158"],"award-info":[{"award-number":["2023JJ40158"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Nanomaterials"],"abstract":"<jats:p>\u03b5-phase indium selenide (\u03b5-InSe), a non-centrosymmetric van der Waals layered semiconductor, exhibits broken inversion symmetry in all layer numbers, giving rise to exceptional second-order nonlinear optical responses and holding great promise for nonlinear optoelectronic applications. The dynamic control of the nonlinear efficiency of \u03b5-InSe is crucial for its engineering applications. However, the quantitative manipulation of second-harmonic generation (SHG) intensity and crystal symmetry in few-layer \u03b5-InSe via strain engineering is still lacking. In this work, we systematically investigate the modulation of SHG intensity and angle-resolved SHG patterns in few-layer \u03b5-InSe under uniaxial tensile strain. Using a home-built straining apparatus, we apply controlled tensile strain and measure the strain-dependent SHG responses. The experimental results demonstrate that the SHG intensity of few-layer \u03b5-InSe shows a non-monotonic response to increasing tensile strain, first increasing and then decreasing. Concurrently, the sixfold symmetry of the SHG pattern is broken, confirming the significant strain-induced modulation of the lattice symmetry. This study provides a viable route for the design of flexible and tunable nonlinear optoelectronic devices based on \u03b5-InSe.<\/jats:p>","DOI":"10.3390\/nano16150964","type":"journal-article","created":{"date-parts":[[2026,8,6]],"date-time":"2026-08-06T09:46:38Z","timestamp":1786009598000},"page":"964","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Strain Engineering of Second-Harmonic Generation and Symmetry Breaking in Few-Layer \u03b5-InSe"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0009-0007-7443-4812","authenticated-orcid":false,"given":"Danliang","family":"Zhang","sequence":"first","affiliation":[{"name":"Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Research Center of the Basic Discipline for Quantum Effects and Quantum Technologies, School of Physics and Electronics, Hunan Normal University, Changsha 410081, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sihan","family":"Liu","sequence":"additional","affiliation":[{"name":"Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Research Center of the Basic Discipline for Quantum Effects and Quantum Technologies, School of Physics and Electronics, Hunan Normal University, Changsha 410081, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Peiran","family":"Li","sequence":"additional","affiliation":[{"name":"Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Research Center of the Basic Discipline for Quantum Effects and Quantum Technologies, School of Physics and Electronics, Hunan Normal University, Changsha 410081, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1652-0049","authenticated-orcid":false,"given":"Qing","family":"Ye","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Pulsed Power Laser Technology, Key Laboratory of Electronic Restriction of Anhui Province, National University of Defense Technology, Advanced Laser Technology Laboratory of Anhui Province, Hefei 230037, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0002-0006-3274","authenticated-orcid":false,"given":"Ying","family":"Chen","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Pulsed Power Laser Technology, Key Laboratory of Electronic Restriction of Anhui Province, National University of Defense Technology, Advanced Laser Technology Laboratory of Anhui Province, Hefei 230037, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,8,6]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"223","DOI":"10.1038\/nnano.2016.242","article-title":"High electron mobility, quantum Hall effect and anomalous optical response in atomically thin InSe","volume":"12","author":"Bandurin","year":"2017","journal-title":"Nat. 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