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| Open AccessPlasma electron acceleration driven by a long-wave-infrared laser
The laser pulses that drive most laser wakefield accelerators have wavelengths near 1 micrometer and peak power > 100 terawatts. Here, the authors drive plasma wakes with 10 micrometer, 2-terawatt pulses, yielding relativistic electron beams with a collimated, narrow-energy-bandwidth component.
- R. Zgadzaj
- , J. Welch
- & M. C. Downer
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Article
| Open AccessPhotonic time-crystalline behaviour mediated by phonon squeezing in Ta2NiSe5
Photonic time crystal refers to a material whose dielectric properties oscillate in time. Here the authors theoretically show such behaviour in the excitonic insulator candidate Ta2NiSe5 under optical excitation and use it to explain the enhanced THz reflectivity recently observed in pump-probe experiments
- Marios H. Michael
- , Sheikh Rubaiat Ul Haque
- & Eugene Demler
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| Open AccessCorrelation-driven nonequilibrium exciton site transition in a WSe2/WS2 moiré supercell
Correlated insulator states of moire excitons in transition metal dichalcogenide heterostructures have attracted significant attention recently. Here the authors use time-resolved pump-probe spectroscopy to demonstrate the effects of non-equilibrium correlations of moire excitons in WSe2/WS2 heterobilayers.
- Jinjae Kim
- , Jiwon Park
- & Hyunyong Choi
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Article
| Open AccessExtreme terahertz magnon multiplication induced by resonant magnetic pulse pairs
The authors demonstrate high-order terahertz nonlinear magnonics using two-dimensional coherent spectroscopy, revealing the emergence of seventh-order spin-wave mixing and sixth harmonic magnon generation within an antiferromagnetic orthoferrite.
- C. Huang
- , L. Luo
- & J. Wang
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| Open AccessDefect-induced helicity dependent terahertz emission in Dirac semimetal PtTe2 thin films
Defect engineering of topological materials provides an avenue for the controllable manipulation of optoelectronic properties. Here, the authors introduce a defect gradient into a Dirac semimetal to control the Berry curvature dipole-driven THz emission in the material.
- Zhongqiang Chen
- , Hongsong Qiu
- & Xuefeng Wang
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| Open AccessRetinal photoisomerization versus counterion protonation in light and dark-adapted bacteriorhodopsin and its primary photoproduct
Malakar et al. investigate the photochemical dynamics in the isomerization of bacteriorhodopsin light and dark-adapted forms and in the first photocycle intermediate, K. The results prompt a reevaluation of the counter ion model, revealing that a different protonation then that shown in the classic quadrupole so far considered must be employed to account for the experimental data.
- Partha Malakar
- , Samira Gholami
- & Sanford Ruhman
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Article
| Open AccessOrbitronics: light-induced orbital currents in Ni studied by terahertz emission experiments
Several recent works have highlighted the importance of the orbital currents in transferring angular momentum within materials. In combination with spin-orbit coupling, such orbital currents can be used to alter the magnetization of a material. Herein, the authors demonstrate the inverse effect, showing orbital current driven terahertz emission in Nickel based heterostructures.
- Yong Xu
- , Fan Zhang
- & Weisheng Zhao
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Article
| Open AccessSwept coded aperture real-time femtophotography
The researchers showcase swept-coded aperture real-time femtophotography—an all-optical single-shot computational imaging modality at up to 156.3 trillion frames per second—video-records transient absorption in a semiconductor and ultrafast demagnetization of a metal alloy.
- Jingdan Liu
- , Miguel Marquez
- & Jinyang Liang
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Article
| Open AccessIntrinsic dichroism in amorphous and crystalline solids with helical light
Differential absorption of polarized light, called dichroism, does not exist in amorphous solids due to the disordered arrangements of atoms. Here, the authors demonstrate that dichroism is intrinsic to all solids and can be controlled using helical light beams carrying orbital angular momentum.
- Ashish Jain
- , Jean-Luc Bégin
- & Ravi Bhardwaj
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| Open AccessReal-time tracking of coherent oscillations of electrons in a nanodevice by photo-assisted tunnelling
The authors demonstrate that the collective electron oscillations driven by light in a quantum nanodevice can be measured directly in the time domain, by recording the photo-assisted tunnelling currents using the technique of homodyne beating.
- Yang Luo
- , Frank Neubrech
- & Manish Garg
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Article
| Open AccessLinear and phase controllable terahertz frequency conversion via ultrafast breaking the bond of a meta-molecule
The time-varying metasurfaces show promise for exploring exotic physics and photonic applications. The authors introduce a time-varying metasurface with superconductor-metal hybrid meta-molecules, demonstrating phase-controllable frequency conversion with high efficiency.
- Siyu Duan
- , Xin Su
- & Peiheng Wu
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Article
| Open AccessAnisotropic carrier dynamics and laser-fabricated luminescent patterns on oriented single-crystal perovskite wafers
Based on differently-oriented MAPbBr3 single-crystal wafers, the authors revealed anisotropic carrier dynamics by using angle-resolved pump-probe technique, and the microstructural mechanism of the femtosecond laser-induced emission enhancement
- Chao Ge
- , Yachao Li
- & Yang Liu
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Article
| Open AccessChirality manipulation of ultrafast phase switches in a correlated CDW-Weyl semimetal
The charge-density-wave Weyl semimetal (TaSe4)2I is a candidate for an axion insulator, however it may be obscured by polaron physics. Here, using ultrafast terahertz photocurrent spectroscopy, the authors realize phase switches from the polaronic state, to the charge density wave phase, and to the Weyl phase.
- Bing Cheng
- , Di Cheng
- & Jigang Wang
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| Open AccessManipulating hyperbolic transient plasmons in a layered semiconductor
Here, the authors report the generation and manipulation of transient hyperbolic plasmons in black phosphorus via ultrafast photocarrier injection, demonstrating a topological transition of the non-equilibrium iso-frequency contours and the coexistence of different transient plasmonic modes.
- Rao Fu
- , Yusong Qu
- & Jianing Chen
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Article
| Open AccessOrbital perspective on high-harmonic generation from solids
Here the authors identify real-space contributions to the characteristics of high-harmonic generation in ReS2 and demonstrate the possibility of laser-controlled emission. They find that the spectrum is not just determined by the band structure, but also by the interference between HHG signals coming from different atoms within the unit cell.
- Álvaro Jiménez-Galán
- , Chandler Bossaer
- & Giulio Vampa
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| Open AccessA coherent phonon-induced hidden quadrupolar ordered state in Ca2RuO4
Ultrafast laser excitation can generate metastable states in quantum materials, with no counterpart in equilibrium. Here the authors demonstrate a transient quadrupolar ordered state in Ca2RuO4 single crystals via excitation of a phonon mode coupled to the order parameter.
- Honglie Ning
- , Omar Mehio
- & David Hsieh
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Article
| Open AccessDiscovery of ultrafast spontaneous spin switching in an antiferromagnet by femtosecond noise correlation spectroscopy
Antiferromagnets exhibit high frequency magnons, in the THz regime, a point potentially useful for applications, however, it has meant that detecting spin-fluctuations in antiferromagnets is typically too fast for current experimental approaches. Here Weiss et al use femtosecond noise correlation spectroscopy to observe magnon fluctuations in Sm0.7Er0.3FeO3.
- M. A. Weiss
- , A. Herbst
- & T. Kurihara
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| Open AccessPhonon-enhanced nonlinearities in hexagonal boron nitride
Nonlinear optical processes like higher-order harmonic generation in solids depend on several factors. Here the authors explore the optical nonlinearity of hexagonal boron nitride and find that enhanced nonlinearity is due to electron-phonon and phonon-polariton couplings.
- Jared S. Ginsberg
- , M. Mehdi Jadidi
- & Alexander L. Gaeta
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| Open AccessStrong transient magnetic fields induced by THz-driven plasmons in graphene disks
The authors provide an experimental demonstration of magnetic field generation in graphene disks via the inverse Faraday effect. When the disks are illuminated with circularly polarized radiation in resonance with the graphene plasmon frequency, the corresponding rotational motion of the charge carriers gives rise to a unipolar magnetic field.
- Jeong Woo Han
- , Pavlo Sai
- & Martin Mittendorff
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| Open AccessEnhanced optical conductivity and many-body effects in strongly-driven photo-excited semi-metallic graphite
Strong optical excitation near band extrema can drive novel correlated states. Here the authors report a non-equilibrium many-body state in graphite driven by a strong excitation near van Hove singularity, yielding a tenfold increase in optical conductivity attributed to carrier excitations in the flat bands.
- T. P. H. Sidiropoulos
- , N. Di Palo
- & J. Biegert
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Article
| Open AccessVisible-to-mid-IR tunable frequency comb in nanophotonics
Here the authors provide the experimental demonstration of a widely tunable integrated frequency comb source unlocking the spectrum from the visible to the mid-infrared in a thin-film lithium niobate platform.
- Arkadev Roy
- , Luis Ledezma
- & Alireza Marandi
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| Open AccessTerahertz radiation by quantum interference of excitons in a one-dimensional Mott insulator
THz pulses with tuneable properties are desirable for manipulating electronic states in materials. The authors report generation of THz pulses with phase, frequency, and amplitude control by tuning exciton interference in a 1D Mott insulator of transition metal complex and provide insight into exciton dynamics.
- Tatsuya Miyamoto
- , Akihiro Kondo
- & Hiroshi Okamoto
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| Open AccessEngineering the temporal dynamics of all-optical switching with fast and slow materials
Here the authors demonstrate the active control of an all-optical switch harnessing the interaction of light with the constituent materials. The response speeds up by two orders of magnitude and scales accordingly with the strength of the light matter interaction.
- Soham Saha
- , Benjamin T. Diroll
- & Alexandra Boltasseva
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Article
| Open AccessElevated concentrations cause upright alpha-synuclein conformation at lipid interfaces
The misfolding of alpha-synuclein is associated with neurodegenerative disorders such as Parkinson’s disease. The authors report a mechanism explaining why lipid membranes catalyze the formation of harmful aggregates at elevated concentrations.
- Steven J. Roeters
- , Kris Strunge
- & Tobias Weidner
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| Open AccessInterplay of valley polarized dark trion and dark exciton-polaron in monolayer WSe2
Here, the authors observe that valley-polarized dark excitons in monolayer WSe2 show a distinct doping dependence when the carriers reach a critical density. This is indicative of the onset of strongly modified Fermi sea interactions.
- Xin Cong
- , Parisa Ali Mohammadi
- & Xiao-Xiao Zhang
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Article
| Open AccessCarrier-envelope phase on-chip scanner and control of laser beams
Measurement and control of the carrier-envelope phase (CEP) is essential for applications of few-cycle laser beams. The authors present a compact on-chip, ambient-air, CEP scanning probe and show a 3D map of spatial changes of CEP and demonstrate CEP control in the focal volume with a spatial light modulator.
- Václav Hanus
- , Beatrix Fehér
- & Péter Dombi
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Article
| Open AccessAttosecond delays between dissociative and non-dissociative ionization of polyatomic molecules
The role of nuclear motion on photoionization delays is an interesting open question. Here the authors study photoionization delays in dissociative and non-dissociative ionization of a polyatomic molecule and explore the effect of isotopic substitution.
- Xiaochun Gong
- , Étienne Plésiat
- & Hans Jakob Wörner
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Article
| Open AccessRevealing core-valence interactions in solution with femtosecond X-ray pump X-ray probe spectroscopy
Pump-probe spectroscopy is routinely used to interrogate ultrafast valence electronic and vibrational dynamics in complex systems. Here, the authors extend this technique to the X-ray regime using a sequence of femtosecond X-ray pulses to understand core-valence interactions in a solvated molecular complex.
- Robert B. Weakly
- , Chelsea E. Liekhus-Schmaltz
- & Munira Khalil
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Article
| Open AccessTwo-photon imaging of soliton dynamics
The authors present a moving-parts-free approach for visualizing soliton motion in optical cavities that lifts the wavelength and speed constraints of contemporary pulsed laser diagnostic techniques.
- Łukasz A. Sterczewski
- & Jarosław Sotor
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| Open AccessDirect observation of coherence transfer and rotational-to-vibrational energy exchange in optically centrifuged CO2 super-rotors
In this work the authors use coherent anti-Stokes Raman scattering to study collisional vibrational excitation in highly rotationally excited CO2 molecules prepared in an optical centrifuge.
- Timothy Y. Chen
- , Scott A. Steinmetz
- & Christopher J. Kliewer
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| Open AccessEpitaxial growth of highly symmetrical branched noble metal-semiconductor heterostructures with efficient plasmon-induced hot-electron transfer
Epitaxial growth of heterostructures composed of materials with large lattice mismatch is challenging. Here, the authors reported the epitaxy of II-VI semiconductor nanorods on plasmonic noble metal, despite a lattice mismatch of more than 40%.
- Li Zhai
- , Sara T. Gebre
- & Xue-Jun Wu
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| Open AccessZero-field quantum beats and spin decoherence mechanisms in CsPbBr3 perovskite nanocrystals
Lead halide perovskites host bright triplet excitons which have applications in optospintronic devices. Here the authors observe quantum coherence between exciton sublevels without magnetic field and clarify the mechanisms of exciton spin relaxation in ensembles of CsPbBr3 nanocrystals.
- Rui Cai
- , Indrajit Wadgaonkar
- & Tze Chien Sum
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Article
| Open AccessUncovering temperature-dependent exciton-polariton relaxation mechanisms in hybrid organic-inorganic perovskites
Exciton-polaritons present opportunities for quantum photonics, next generation qubits, and tuning material photophysics. Here Laitz et al. study the temperature dependence of 2D perovskite microcavity polaritons, revealing material-specific relaxation mechanisms towards the control of polariton momentum.
- Madeleine Laitz
- , Alexander E. K. Kaplan
- & Vladimir Bulović
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| Open AccessHigh-harmonic generation from a flat liquid-sheet plasma mirror
High-harmonic generation (HHG) is a nonlinear process and has been explored with different forms of plasma target. Here the authors report HHG using a liquid plasma mirror as a possible way for the generation of stable and intense attosecond pulses at a high-repetition rate.
- Yang Hwan Kim
- , Hyeon Kim
- & Kyung Taec Kim
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| Open AccessUnveiling the complexity of spatiotemporal soliton molecules in real time
The authors present the real-time spectral-temporal dynamics of 3D soliton molecules, highlighting the importance of nonlinear spatiotemporal coupling in the dynamics of spatiotemporal mode-locking.
- Yuankai Guo
- , Wei Lin
- & Zhongmin Yang
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| Open AccessGeneration of third-harmonic spin oscillation from strong spin precession induced by terahertz magnetic near fields
The authors studied HoFeO3 crystal using multicycle THz magnetic pulses enhanced strongly by spiral-shaped microstructure. The observed Faraday ellipticity demonstrates second- and third-order harmonics of the magnetization oscillation and an asymmetric oscillation behavior.
- Zhenya Zhang
- , Fumiya Sekiguchi
- & Hideki Hirori
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| Open AccessThe importance of the interface for picosecond spin pumping in antiferromagnet-heavy metal heterostructures
By placing an antiferromagnet next to a heavy metal such as platinum, magnetic excitations in the antiferromagnet drive a spin current in the heavy metal, leading to terahertz emission. Here, Kholid et al study the terahertz emission of two antiferromagnets, KCoF3 and KNiF3 with very different magnon frequencies, and find that the opening of a gap in the magnon density of states drastically alters the spin-transfer efficiency.
- Farhan Nur Kholid
- , Dominik Hamara
- & Chiara Ciccarelli
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Article
| Open AccessGigahertz optoacoustic vibration in Sub-5 nm tip-supported nano-optomechanical metasurface
Nano-optomechanical systems plays an indispensable role in all-optical manipulation of light but high energy losses severely limit their development. Here the authors show ultrafast all-optical manipulation in a sub-5 nm tip-supported optomechanical metasurface.
- Renxian Gao
- , Yonglin He
- & Zhilin Yang
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Article
| Open AccessExperimental realisations of the fractional Schrödinger equation in the temporal domain
Studies on the fractional Schrödinger equation (FSE) remain mostly theoretical, due to the lack of materials supporting fractional dispersion or diffraction. Here, the authors indirectly realized the FSE using two programmable holograms acting as an optical Lévy waveguide.
- Shilong Liu
- , Yingwen Zhang
- & Ebrahim Karimi
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Article
| Open AccessOnset of Bloch oscillations in the almost-strong-field regime
There are many possible mechanisms of high-harmonic generation from crystals. Here the authors discuss the role of the Bloch oscillation to nonlinear response of the crystal and harmonic radiation from it.
- Jan Reislöhner
- , Doyeong Kim
- & Adrian N. Pfeiffer
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Article
| Open AccessDynamic complex opto-magnetic holography
Holography recreates both the amplitude and wave front of a three dimensional object, meaning that the observer perceives the image in the nearly same way as they would the true object. Creating such holographic images is challenging computationally, and requires extremely fast display update. Here, the authors combine a fast memoryless computation algorithm with the ultra-rapid writing based on all-optical switching of a ferrimagnetic film.
- M. Makowski
- , J. Bomba
- & A. Stupakiewicz
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Article
| Open AccessControlling Floquet states on ultrashort time scales
Floquet engineering aims at inducing new properties in materials with light. Here the authors have used pulses of variable durations, to investigate its applicability in the femtosecond domain. Surprisingly, they found that it holds to the few-cycle limit.
- Matteo Lucchini
- , Fabio Medeghini
- & Mauro Nisoli
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Article
| Open AccessStrongly enhanced THz generation enabled by a graphene hot-carrier fast lane
THz imaging and spectroscopy always request even more efficient components. Here the authors, thanks to a modified photoconductive switch that includes a graphene layer, demonstrate a high-speed photoconductive switch without sacrificing the generated power.
- Dehui Zhang
- , Zhen Xu
- & Zhaohui Zhong
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Article
| Open AccessSynthesized spatiotemporal mode-locking and photonic flywheel in multimode mesoresonators
Here the authors demonstrate spatiotemporal mode-locked dissipative Kerr soliton and enhanced photonic flywheel performances in both the fundamental comb linewidth and DKS timing jitter.
- Mingming Nie
- , Kunpeng Jia
- & Shu-Wei Huang
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Article
| Open AccessOptoelectronic properties and ultrafast carrier dynamics of copper iodide thin films
Deep understanding of defect physics, excitonic properties and the ultrafast carrier dynamics in the high mobility p-type transparent CuI is vital for its optoelectronic applications. Here, Liu et al. employ a synergistic approach to unveil these fundamental properties.
- Zhan Hua Li
- , Jia Xing He
- & Chao Ping Liu
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Article
| Open AccessSub-optical-cycle light-matter energy transfer in molecular vibrational spectroscopy
Energy transfer between the electromagnetic field and atoms or molecules is fundamentally interesting. Here the authors demonstrate stepwise energy transfer between broadband mid-infrared optical pulses and vibrating methylsulfonylmethane molecules in aqueous solution.
- Martin T. Peschel
- , Maximilian Högner
- & Ioachim Pupeza
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Article
| Open AccessAtomic partial wave meter by attosecond coincidence metrology
Understanding the photoelectron emission time after the interaction of photon with atoms and molecules is of fundamental interest. Here the authors examine the role of partial waves to the photoionization phase shift of atoms using an attosecond clock and electron-ion coincidence spectroscopy.
- Wenyu Jiang
- , Gregory S. J. Armstrong
- & Jian Wu
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Article
| Open AccessK-point longitudinal acoustic phonons are responsible for ultrafast intervalley scattering in monolayer MoSe2
Valley depolarization processes in 2D transition metal dichalcogenides have been linked to acoustic phonons, but optical verification is ambiguous, due to the nearly degenerate acoustic phonon frequencies at the zone-edge. Here, the authors determine the phonon momentum of the longitudinal acoustic (LA) phonons at the K point as responsible for the ultrafast valley depolarization in monolayer MoSe2.
- Soungmin Bae
- , Kana Matsumoto
- & Ikufumi Katayama
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Article
| Open AccessElectric-field control of nonlinear THz spintronic emitters
Spintronic terahertz (THz) emitters are a class of magnetic heterostructure where femtosecond laser excitations generate THz radiation emission. While they have great potential, electric field control of spintronic emitter remains a challenge. Here, by combining a spintronic emitter with a piezoelectric substrate, Agarwal et al. demonstrate electric field control of THz emission through induced piezostrain.
- Piyush Agarwal
- , Lisen Huang
- & Ranjan Singh