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-derived materials
摘要： Symmetry and dimensionality are essential factors defining lattice dynamics and conductivity (κ). Here, we critically examine these via ab initio Boltzmann transport applied to single chain and bulk electride Ba3N and Ba3NX (X = Sb,Bi). Chiral phonons in one-dimensional chains obey new symmetry-based scattering rules that limit thermal resistance. Weak chain coupling breaks these in the bulk, giving lower κ and large κ anisotropy. Curiously, intercalation of large X atoms binds chains more strongly, reducing the volume, yet gives lower κ and transforms the electronic behavior. Insights developed here can be more generally applied to other materials and provide avenues for predictive materials design.
关键词： symmetry,lattice dynamics,Ba3NX,dimensionality,thermal conductivity,Ba3N,chiral phonons,electride
更新于2025-09-09 09:28:46
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Ultrafast optical control of multiple coherent phonons in silicon carbide using a pulse-shaping technique
摘要： We demonstrated ultrafast optical control of multiple coherent phonons in silicon carbide (SiC) using a pulse-shaping technique combined with sub-10-fs optical pulses and a two-dimensional spatial light modulator. Because our technique produces a pulse train with the desired number of pulses and time intervals, precise manipulation of the amplitudes of the zone-folded optical and acoustic phonon modes could be achieved simultaneously and was well reproduced by a model calculation assuming the two modes are excited independently by each pulse. These results show that our scheme can provide high controllability of multiple phonon modes in SiC.
关键词： pulse-shaping technique,coherent phonons,ultrafast optical control,silicon carbide
更新于2025-09-09 09:28:46
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Investigation of gold/GaN nanorod arrays for hypersonic detection: The effect of periodicity
摘要： Gold nanodisk arrays on the upper surface of GaN nanorods were developed with the aim of achieving hypersonic imaging with a detection frequency above 10 GHz. In this paper, we report the interesting phenomenon that the hypersonic signal detected by a single gold nanodisk in this structure might be dependent on the array periodicity and rod length. When the array periodicity is of the same order of or longer than the surface hypersonic wavelength, the detected signal would be enhanced by the period-dependent resonance of the surface hypersonic waves scattered by the nanorod/substrate interface. When the array periodicity is smaller than the surface hypersonic wavelength, the coupling of extensional modes between neighboring nanorods, as the detection frequency approaches the coupled-extensional-mode frequency, would enhance the detected signals. Although these enhancements are beneficial to heat transport at nanorod/substrate interfaces, they will cause cross-talk between the neighboring detection rod unit and should be avoided by choosing the correct period for imaging array applications. Our result further indicates that the extensional mode coupling could be avoided by increasing the rod-length to shift the extensional mode frequency away from the detection frequency. This work not only investigates the transport behavior of hypersonic-frequency acoustic phonons at the interface between a bulk material and a nanostructure, but also suggests that the effects of the periodicity and nanorod length need to be taken into consideration for the design of future hypersonic imaging arrays.
关键词： acoustic phonons,periodicity,gold/GaN nanorod arrays,imaging arrays,hypersonic detection
更新于2025-09-09 09:28:46
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Strong Coupling of Folded Phonons with Plasmons in 6H-SiC Micro/Nanocrystals
摘要： Silicon carbide (SiC) has a large number of polytypes of which 3C-, 4H-, 6H-SiC are most common. Since different polytypes have different energy gaps and electrical properties, it is important to identify and characterize various SiC polytypes. Here, Raman scattering is performed on 6H-SiC micro/nanocrystal (MNC) films to investigate all four folded transverse optic (TO) and longitudinal optic (LO) modes. With increasing film thickness, the four folded TO modes exhibit the same frequency downshift, whereas the four folded LO modes show a gradually-reduced downshift. For the same film thickness, all the folded modes show larger frequency downshifts with decreasing MNC size. Based on plasmons on MNCs, these folded modes can be attributed to strong coupling of the folded phonons with plasmons which show different strengths for the different folded modes while changing the film thickness and MNC size. This work provides a useful technique to identify SiC polytypes from Raman scattering.
关键词： folded phonons,SiC micro/nanocrystals,plasmon–phonon coupling
更新于2025-09-04 15:30:14
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Entanglement of single-photons and chiral phonons in atomically thin WSe2
摘要： Quantum entanglement is a fundamental phenomenon that, on the one hand, reveals deep connections between quantum mechanics, gravity and spacetime1,2, and on the other hand, has practical applications as a key resource in quantum information processing3. Although it is routinely achieved in photon–atom ensembles4, entanglement involving solid-state5–7 or macroscopic objects8 remains challenging albeit promising for both fundamental physics and technological applications. Here, we report entanglement between collective, chiral vibrations in a two-dimensional WSe2 host—chiral phonons (CPs)—and single-photons emitted from quantum dots9–13 (QDs) present in it. CPs that carry angular momentum were recently observed in WSe2 and are a distinguishing feature of the underlying honeycomb lattice14,15. The entanglement results from a ‘which-way’ scattering process, involving an optical excitation in a QD and doubly-degenerate CPs, which takes place via two indistinguishable paths. Our unveiling of entanglement involving a macroscopic, collective excitation together with strong interactions between CPs and QDs in two-dimensional materials opens up ways for phonon-driven entanglement of QDs and engineering chiral or non-reciprocal interactions at the single-photon level.
关键词： chiral phonons,WSe2,two-dimensional materials,quantum dots,Quantum entanglement
更新于2025-09-04 15:30:14
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Isotopic effects on phonons and excitons in diamond studied by deep-ultraviolet continuous-wave photoluminescence spectroscopy
摘要： Photoluminescence (PL) spectroscopy is performed for natural-abundance (N.A.C) and isotopically purified (13C) synthetic diamond using a deep-ultraviolet continuous-wave laser. Because the excitation source creates low-density low-temperature excitons even under a moderate excitation power, the PL spectra show suppressed collisional and thermal broadening with a high signal-to-noise ratio. Our approach can accurately resolve the isotopic effects. The experimentally determined effects for phonons and excitons in diamond are ΔETA = ?2.5 meV, ΔETO = ?4.9 meV, ΔELO = ?5.7 meV, and ΔEex = 14.5 meV.
关键词： diamond,photoluminescence spectroscopy,isotopic effects,excitons,phonons
更新于2025-09-04 15:30:14
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Physically based Diagonal Treatment of the Self-Energy of Polar Optical Phonons: Performance Assessment of III-V Double-Gate Transistors
摘要： We propose a diagonal approximation for the self-energy that describes the interaction between electrons and polar optical phonons in the framework of nonequilibrium Green’s function transport simulations. Our model is based on the definition of a scaling factor, which renormalizes the local electron-phonon coupling, to take into account the nonlocality of the interaction and provide the correct scattering rates. While previous studies relied on empirical values of this factor, we derive, from basic physical relationships, analytical expressions in the presence of the one- and two-dimensional confinement of phonons. We apply our model to the self-consistent simulation of double-gate p-type transistors made of technologically relevant III-V materials (InAs, InSb, and GaSb). Their performance is benchmarked, for different crystallographic orientations and strain constraints, against the corresponding Si and Ge devices. We find that the electron-polar optical phonon scattering plays a major role in degrading the performance of the III-V devices and typically results in a widening of the performance gap existing between III-V and Si or Ge devices in ballistic transport conditions.
关键词： nonequilibrium Green’s function,electron-phonon scattering,double-gate transistors,self-energy,III-V materials,polar optical phonons
更新于2025-09-04 15:30:14