Probing strong electron-phonon coupling in semimetallic PtSe₂ via ultrafast optical spectroscopy

Abstract

Platinum diselenide (PtSe₂) exhibits a distinctive thickness-modulated metal-to-semiconductor transition, which makes it suitable for diverse applications in nanoelectronics and optoelectronics. This study systematically investigates the spatiotemporal dynamics of photoexcited carrier relaxation in PtSe₂. Through temperature-dependent ultrafast spectroscopy, two distinct low-frequency acoustic phonons (AP) were identified in multilayer PtSe₂. Transient absorption microscopy (TAM) measurements reveal thickness-dependent relaxation dynamics and distinct carrier diffusion behavior in multilayer PtSe₂. These findings indicate superior carrier transport properties, with a measured mobility of 394.1±38.5 cm²·V⁻¹·s⁻¹ for multilayers. Temperature-dependent ultrafast dynamics, acquired using a custom-built cryogenic pump-probe system, reveal two coherent AP modes, ω₁ and ω₂, with central frequencies of 1.27 and 0.17 THz, respectively. The higher frequency ω₁ mode corresponds to shear mode with a nominal electron-phonon coupling constant λ_ω1 = 2.22. To our knowledge, this study represents a pioneering investigation that employs low-temperature ultrafast spectroscopy to elucidate the AP mode and strong electron-phonon coupling in semimetallic PtSe₂ systems. These findings offer fundamental insights into the semimetallic nature of PtSe₂ and establish a basis for designing ultrafast photonic devices that harness its distinct optoelectronic response.

Keywords

PtSe₂ / thickness-modulated / electron-phonon coupling / ultrafast optical / low-temperature

References

[1] Yu X-c, Yu P, Wu D, et al.. Atomically thin noble metal dichalcogenide: A broadband mid-infrared semiconductor [J]. Nature Communications, 2018, 9: 1545

[2] Yu J, Kuang X-f, Gao Y-j, et al.. Direct observation of the linear dichroism transition in two-dimensional palladium diselenide [J]. Nano Letters, 2020, 20(2): 1172-1182

[3] Niu W-h, Pakhira S, Cheng G-m, et al.. Reaction-driven restructuring of defective PtSe₂ into ultrastable catalyst for the oxygen reduction reaction [J]. Nature Materials, 2024, 23(12): 1704-1711

[4] Wang Y-l, Li L-f, Yao W, et al.. Monolayer PtSe2, a new semiconducting transition-metal-dichalcogenide, epitaxially grown by direct selenization of Pt [J]. Nano Letters, 2015, 15(6): 4013-4018

[5] Zhao Y-d, Qiao J-s, Yu Z-h, et al.. High-electron-mobility and air-stable 2D layered PtSe₂ FETs [J]. Advanced Materials, 2017, 29(5): 1604230

[6] Zhang W-x, Huang Z-s, Zhang W-l, et al.. Two-dimensional semiconductors with possible high room temperature mobility [J]. Nano Research, 2014, 7(12): 1731-1737

[7] Qu Z-h, Zhang Y-h, Zhao X-w, et al.. Highperformance bilayer sliding PtSe₂ infrared photodetector [J]. Chinese Physics Letters, 2025, 42(5): 058101

[8] Liu X, Deng C-y, Wei H, et al.. High-sensitive uncooled mid-wave infrared photodetector based on PtSe₂/MoTe₂ heterojunction with fast speed [J]. Advanced Functional Materials, 2025, 35(30): 2423102

[9] Zhang W-l, Chen H, Peng J-b, et al.. Unraveling the interfacial carrier behavior in PtSe₂-MoSe₂ heterostructures: Insights from combined pump-probe spectroscopy and scanning tunneling microscopy [J]. Advanced Science, 2025, 12(17): 2500598

[10] Wang Y-w, Zhou L, Zhong M-z, et al.. Two-dimensional noble transition-metal dichalcogenides for nanophotonics and optoelectronics: Status and prospects [J]. Nano Research, 2022, 15(4): 3675-3694

[11] Wang G-z, Wang Z-z, Mcevoy N, et al.. Layered PtSe₂ for sensing, photonic, and (opto-) electronic applications [J]. Advanced Materials, 2021, 33(1): 2004070

[12] Gyeon M, Seo J E, Oh S, et al.. Wafer-scale growth of ultrauniform 2D PtSe₂ films with spatial and thickness control through multi-step metal conversion [J]. ACS Nano, 2024, 18(50): 33977-33987

[13] Yim C, Lee K, Mcevoy N, et al.. High-performance hybrid electronic devices from layered PtSe₂ films grown at low temperature [J]. ACS Nano, 2016, 10(10): 9550-9558

[14] Han J, Wang Y-w, He J, et al.. Fabry - Perot cavity enhanced three-photon luminescence of atomically thin platinum diselenide [J]. Nanoscale, 2021, 13(19): 9031-9038

[15] Mak K F, Lee C, Hone J, et al.. Atomically ThinMoS₂: A new direct-gap semiconductor [J]. Physical Review Letters, 2010, 105(13): 136805

[16] Yuan J, Mu H-r, Li L, et al.. Few-layer platinum diselenide as a new saturable absorber for ultrafast fiber lasers [J]. ACS Applied Materials & Interfaces, 2018, 10(25): 21534-21540

[17] Wang G-z, Wang K-p, Mcevoy N, et al.. Ultrafast carrier dynamics and bandgap renormalization in layered PtSe₂ [J]. Small, 2019, 15(34): 1902728

[18] Wang L, Zhang S-f, Mcevoy N, et al.. Nonlinear optical signatures of the transition from semiconductor to semimetal in PtSe₂ [J]. Laser & Photonics Reviews, 2019, 13(8): 1900052

[19] Zheng Z-s, Peng Z, Yu Z-s, et al.. Thickness-dependent optical response and ultrafast carrier dynamics of PtSe₂ films [J]. Results in Physics, 2022, 42: 106012

[20] Wang P-z, He D-w, Wang Y-s, et al.. Fast exciton diffusion in monolayer PtSe₂ [J]. Laser & Photonics Reviews, 2022, 16(7): 2100594

[21] Wang Y-w, Deng Z-l, Hu D-j, et al.. Atomically thin noble metal dichalcogenides for phaseregulated meta-optics [J]. Nano Letters, 2020, 20(11): 7811-7818

[22] Lee C, Yan H-g, Brus L E, et al.. Anomalous lattice vibrations of single- and few-layer MoS₂ [J]. ACS Nano, 2010, 4(5): 2695-2700

[23] Yan M-z, Wang E-y, Zhou X, et al.. High quality atomically thin PtSe₂ films grown by molecular beam epitaxy [J]. 2D Materials, 2017, 4(4): 045015

[24] Yue S, Tian F, Sui X-y, et al.. High ambipolar mobility in cubic boron arsenide revealed by transient reflectivity microscopy [J]. Science, 2022, 377(6604): 433-436

[25] Feng X-k, Tan J-y, Cao X-q, et al.. High ambipolar mobility and long-range carrier transport in violet phosphorus nanosheet [J]. Nano Letters, 2024, 24(33): 10348-10354

[26] Zhang C, Wu Q-y, Hong W-s, et al.. Ultrafast optical spectroscopy evidence of pseudogap and electron-phonon coupling in an iron-based superconductor KCa₂Fe₄As₄F2 [J]. Science China Physics, Mechanics & Astronomy, 2022, 65(3): 237411

[27] Liu S-y, Zhu S-x, Wu Q-y, et al.. Dirac semimetal PdTe₂ temperature-dependent quasiparticle dynamics and electron - phonon coupling [J]. Results in Physics, 2021, 30: 104816

[28] Liu H, Zhang C, Wu Q-y, et al.. Ultrafast photoinduced phase transition in the antiferromagnetic Dirac semimetal EuAgAs [J]. Physical Review B, 2025, 111(12): L121113

[29] Kabanov V V, Alexandrov A S. Electron relaxation in metals: Theory and exact analytical solutions [J]. Physical Review B, 2008, 78(17): 174514

[30] Sun F, Yang M, Yang M-w, et al.. Coherent acoustic phonon and its chirping in Dirac semimetal Cd₃As₂ [J]. Chinese Physics Letters, 2018, 35(11): 64-70 in Chinese)

[31] Kandemir A, Akbali B, Kahraman Z, et al.. Structural, electronic and phononic properties of PtSe₂: From monolayer to bulk [J]. Semiconductor Science and Technology, 2018, 33(8): 085002

[32] Bardeen J, Cooper L N, Schrieffer J R. Theory of superconductivity [J]. Physical Review, 1957, 108(5): 1175-1204

[33] Si C, Liu Z, Duan W-h, et al.. First-principles calculations on the effect of doping and biaxial tensile strain on electron-phonon coupling in graphene [J]. Physical Review Letters, 2013, 111(19): 196802

[34] Zhang B-y, Guo F, Zhu M-f, et al.. The sensitive tunability of superconducting critical temperature in high-buckled plumbene by shifting Fermi level [J]. Physica E: Low-dimensional Systems and Nanostructures, 2021, 130: 114688

[35] Yuan Y-h, Duan Y-x, Wang Z-w, et al.. Filamentary superconductivity in wrinkled PtSe₂ [J]. Journal of Physics D: Applied Physics, 2021, 54(21): 215302

[36] Young S M, Zaheer S, Teo J C Y, et al.. Dirac semimetal in three dimensions [J]. Physical Review Letters, 2012, 108(14): 140405

[37] Xu S-y, Belopolski I, Alidoust N, et al.. Discovery of a Weyl fermion semimetal and topological Fermi arcs [J]. Science, 2015, 349(6248): 613-617

[38] Song Z-d, Zhao J-m, Fang Z, et al.. Detecting the chiral magnetic effect by lattice dynamics in Weyl semimetals [J]. Physical Review B, 2016, 94(21): 214306

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Central South University