Resonant and nonresonant control over matter and light by intense terahertz transients

Kampfrath, Tobias; Tanaka, Kōichiro; Nelson, Keith A.

doi:10.1038/nphoton.2013.184

Cited by 896 publications

(643 citation statements)

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“…2). For example, intense THz fields 44 in the range 10 6 -10 7 V cm -1 can be generated across a broad swath of the electromagnetic spectrum to drive quantum phases at their natural energy scales. The electric field can be further enhanced by integrating quantum materials with metamaterials 45 .…”

Section: Nature Materials Doi: 101038/nmat5017mentioning

confidence: 99%

“…Tunnelling dominates for γ < 1, while multiphoton absorption dominates for γ > 1. For sufficiently high fields (1-10 MV cm -1 ) at THz and mid-infrared frequencies, the tunnelling regime (γ < 1) is operative, resulting in novel phenomena and unexpected effects such as massive population transfer between bands far in excess of the photon energy (that is, E g >> ħω) 44,48,49 . An exciting research direction that will remain outside of the scope of this Review is the electrical and optical control of magnetism 50,51 .…”

Section: Nature Materials Doi: 101038/nmat5017mentioning

confidence: 99%

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Towards properties on demand in quantum materials

2017

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Q uantum materials are on the ascent. This term embodies a vast portfolio of compounds and phenomena where ramifications of quantum mechanics are demonstrably real. Quantum materials are in the vanguard of contemporary physics in part because these systems afford an exceptional venue to uncover the many roles of symmetry, topology, dimensionality and strong correlations in macroscopic observables. Here we set out to explore the ways and means of creating new states of matter in quantum materials and manipulating their phases via external stimuli. Practical control of these properties is a precondition for exploiting quantum advantages in new photonic, electronic and energy technologies, a task of significant societal impact 1 . We will primarily focus on the following classes of quantum materials: transition metal oxides, Fe-and Cu-based high-T c superconductors, van der Waals semiconductors, topological insulators and Weyl semimetals, and, finally, graphene.The properties of quantum materials are anomalously sensitive to external stimuli. In these systems, interactions associated with spin, charge, lattice and orbital degrees of freedom are commonly on par with the electronic kinetic energy. A rather fragile balance between coexisting and competing ground states can be readily shifted via external stimuli, leading to a raft of quantum phases and transitions between them 2,3 . Furthermore, certain classes of driven quantum states (Fig. 1a and Box 1) are explicit products of coherent interaction between light and matter 4-6 . Alternatively, the properties of quantum materials can be pre-programmed by directly manipulating the electronic wavefunction and the attendant Berry phase that give rise to the anomalous velocity of electrons in a solid [7][8][9] . These complementary avenues of controls mean that investigations no longer need to be reduced to merely observing (in contrast, for example, to astrophysics). Instead, it is now feasible to attain, in a predictable fashion, 'properties on demand' by steering a quantum material towards a desirable ground, metastable or transient state. The past decade has witnessed an explosion in the field of quantum materials, headlined by the predictions and discoveries of novel Landau-symmetry-broken phases in correlated electron systems, topological phases in systems with strong spin-orbit coupling, and ultra-manipulable materials platforms based on two-dimensional van der Waals crystals. Discovering pathways to experimentally realize quantum phases of matter and exert control over their properties is a central goal of modern condensed-matter physics, which holds promise for a new generation of electronic/photonic devices with currently inaccessible and likely unimaginable functionalities. In this Review, we describe emerging strategies for selectively perturbing microscopic interaction parameters, which can be used to transform materials into a desired quantum state. Particular emphasis will be placed on recent successes to tailor electronic interaction parameters through th...

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Section: Nature Materials Doi: 101038/nmat5017mentioning

confidence: 99%

Section: Nature Materials Doi: 101038/nmat5017mentioning

confidence: 99%

Towards properties on demand in quantum materials

2017

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Section: Introductionmentioning

confidence: 99%

“…As this region coincides with many fundamental resonances of materials, THz radiation enables very selective spectroscopic insights into all phases of matter with high temporal 3,4 and spatial 5,6,7,8 resolution. Consequently, numerous applications in basic research 3,4 , imaging 5 and quality control 8 have emerged.To fully exploit the potential of THz radiation, energy-efficient and low-cost sources of ultrashort THz pulses are required. Most broadband table-top emitters are driven by femtosecond laser pulses that generate the required THz charge current by appropriately mixing the various optical frequencies 9,10 .…”

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confidence: 99%

Efficient metallic spintronic emitters of ultrabroadband terahertz radiation

Seifert¹,

Jaiswal²,

Martens³

et al. 2016

Nature Photon

692

802

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Terahertz electromagnetic radiation is extremely useful for numerous applications such as imaging and spectroscopy. Therefore, it is highly desirable to have an efficient table-top emitter covering the 1-to-30-THz window whilst being driven by a low-cost, low-power femtosecond laser oscillator. So far, all solid-state emitters solely exploit physics related to the electron charge and deliver emission spectra with substantial gaps. Here, we take advantage of the electron spin to realize a conceptually new terahertz source which relies on tailored fundamental spintronic and photonic phenomena in magnetic metal multilayers: ultrafast photo-induced spin currents, the inverse spin-Hall effect and a broadband Fabry-Pérot resonance. Guided by an analytical model, such spintronic route offers unique possibilities for systematic optimization. We find that a 5.8-nm-thick W/CoFeB/Pt trilayer generates ultrashort pulses fully covering the 1-to-30-THz range. Our novel source outperforms laser-oscillatordriven emitters such as ZnTe(110) crystals in terms of bandwidth, terahertz-field amplitude, flexibility, scalability and cost. IntroductionThe terahertz (THz) window, loosely defined as the frequency range from 0.3 to 30 THz in the electromagnetic spectrum, is located between the realms of electronics and optics 1,2 . As this region coincides with many fundamental resonances of materials, THz radiation enables very selective spectroscopic insights into all phases of matter with high temporal 3,4 and spatial 5,6,7,8 resolution. Consequently, numerous applications in basic research 3,4 , imaging 5 and quality control 8 have emerged.To fully exploit the potential of THz radiation, energy-efficient and low-cost sources of ultrashort THz pulses are required. Most broadband table-top emitters are driven by femtosecond laser pulses that generate the required THz charge current by appropriately mixing the various optical frequencies 9,10 . Sources made from solids usually consist of semiconducting or insulating structures with naturally or artificially broken inversion symmetry. When the incident photon energy is below the semiconductor band gap, optical rectification causes a charge displacement that follows the intensity envelope of the incident pump pulse 9,10,11,12,13,14,15,16,17 . For above-band-gap excitation, the response is dominated by a photocurrent 18,19,20,21,22,23,24 with a temporally step-like onset and, thus, generally smaller bandwidth than optical rectification 9 . Apart from rare exceptions 14 , however, most semiconductors used are polar 1,2,12,13,15,16,17,21,22 and strongly attenuate THz radiation around optical phonon resonances, thereby preventing emission in the so-called Reststrahlen band located between ~1 and 15 THz.The so far most promising sources covering the full THz window are photocurrents in transient gas plasmas 9,10,25,26,27,28,29 . The downside of this appealing approach is that the underlying ionization process usually requires amplified laser pulses with high threshold energies on the order of 0....

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“…Photocontrol of condensed matter systems has gained continuing interests over decades, [1][2][3] e.g. in semiconductors, 4,5) Mott insulators, 3,[6][7][8][9] spin crossover complexes, [10][11][12] and superconductors.…”

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confidence: 99%

Rate Equation Analysis of the Dynamics of First-order Exciton Mott Transition

Sekiguchi

Shimano

2017

J. Phys. Soc. Jpn.

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We performed a rate equation analysis on the dynamics of exciton Mott transition (EMT) with assuming a detailed balance between excitons and unbound electron-hole (e-h) pairs. Based on the Saha equation with taking into account the empirical expression for the band-gap renormalization effect caused by the unbound e-h pairs, we show that the ionization ratio of excitons exhibits a bistability as a function of total e-h pair density at low temperatures. We demonstrate that an incubation time emerges in the dynamics of EMT from oversaturated exciton gas phase on the verge of the bistable region. The incubation time shows a slowing down behavior when the pair density approaches toward the saddle-node bifurcation of the hysteresis curve of the exciton ionization ratio.Photocontrol of condensed matter systems has gained continuing interests over decades, [1][2][3] e.g. in semiconductors, 4,5) Mott insulators, 3,6-9) spin crossover complexes, [10][11][12] and superconductors. 13,14) Among diverse material systems, photoexcited electron-hole (e-h) systems in semiconductors offer a unique arena to study the rich variety of phases emergent in many particle systems, and their non-equilibrium dynamics. 4,15) One of the intriguing aspects of e-h systems is that the strength of inter-particle Coulomb interaction can be effectively controlled by changing the density of photoexcited carriers through the screening effect, by simply changing the excitation light intensity. The change of the Coulomb interaction causes a phase transition, or crossover, from the insulating exciton gas phase in the low density regime to the metallic e-h plasma in the high density regime, referred to as exciton Mott transition (EMT). There is a long-standing argument whether EMT is a crossover or a first-order phase transition accompanied by a bistability at sufficiently low temperatures. [16][17][18][19][20][21][22] In general, bistability appears in diverse systems such as electronic circuits, optoelectronic systems, magnetic systems, molecular and biological systems, etc. Figure

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Resonant and nonresonant control over matter and light by intense terahertz transients

Cited by 896 publications

References 100 publications

Towards properties on demand in quantum materials

Towards properties on demand in quantum materials

Efficient metallic spintronic emitters of ultrabroadband terahertz radiation

Rate Equation Analysis of the Dynamics of First-order Exciton Mott Transition

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