Rotational Anisotropy Nonlinear Harmonic Generation

Torchinsky, Darius; Hsieh, David

doi:10.1007/978-3-662-52780-1_1

Cited by 7 publications

(4 citation statements)

References 213 publications

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“…We emphasize that in contrast with the spontaneous symmetry breaking seen in conventional photoinduced phase transitions [45,46], the symmetry breaking observed here is explicit and originates from the photoexcitation process itself. In this regard, the symmetry resolution gained from nonlinear optical probes like SHG provides a completely generic and robust framework for characterizing light-induced changes in the nonequilibrium state, as no underlying assumptions or reliance on theoretical models are required [5,6]. While previous studies have reported explicit symmetry breaking from polarization-dependent photoexcitation in Bi and Sb that results from the coupling of phonons to a transiently excited charge density in k-space [47][48][49], we propose an alternative mechanism: the lowering of 4mm1 symmetry to 1 following optical excitation in TaAs arises from photocurrent generation and thus is of purely electronic origin.…”

Section: Resultsmentioning

confidence: 99%

“…Conventional probes of symmetry rely on diffractive techniques, like x-ray, neutron, and electron scattering, to determine the respective lattice, magnetic, and charge ordering in a crystal. Nonlinear optics is also an effective probe of symmetry, as the nonlinear response is described by a third (or higher) rank tensor [5,6], allowing for phases hidden to linear probes (e.g., in correlated electron systems) to be revealed [27][28][29][30]. In the transition metal monopnictide (TMMP) family of WSMs, the lack of inversion symmetry resulting from a polar c-axis leads to an especially strong nonlinear optical response, with significant contributions from the generation of helicity-dependent injection [31][32][33] and helicityindependent shift [32,[34][35][36] photocurrents.…”

Section: Introductionmentioning

confidence: 99%

“…While previous studies have focused on controlling symmetry via coupling to the crystal lattice [1][2][3][4], we demonstrate here an all-electronic mechanism based on photocurrent generation. Using second-harmonic generation spectroscopy as a sensitive probe of symmetry changes [5,6], we observe an ultrafast breaking of time-reversal and spatial symmetries following femtosecond optical excitation in the prototypical type-I Weyl semimetal TaAs. Our results show that optically driven photocurrents can be tailored to explicitly break electronic symmetry in a generic fashion, opening up the possibility of driving phase transitions between symmetry-protected states on ultrafast time scales.…”

Section: Introductionmentioning

confidence: 99%

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Photocurrent-driven transient symmetry breaking in the Weyl semimetal TaAs

Sirica¹,

Orth²,

Scheurer³

et al. 2020

Preprint

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Symmetry plays a central role in conventional and topological phases of matter, making the ability to optically drive symmetry changes a critical step in developing future technologies that rely on such control. Topological materials, like the newly discovered topological semimetals, are particularly sensitive to a breaking or restoring of time-reversal and crystalline symmetries, which affect both bulk and surface electronic states. While previous studies have focused on controlling symmetry via coupling to the crystal lattice, we demonstrate here an all-electronic mechanism based on photocurrent generation. Using second-harmonic generation spectroscopy as a sensitive probe of symmetry changes, we observe an ultrafast breaking of time-reversal and spatial symmetries following femtosecond optical excitation in the prototypical type-I Weyl semimetal TaAs. Our results show that optically driven photocurrents can be tailored to explicitly break electronic symmetry in a generic fashion, opening up the possibility of driving phase transitions between symmetry protected states on ultrafast time scales.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Photocurrent-driven transient symmetry breaking in the Weyl semimetal TaAs

Sirica¹,

Orth²,

Scheurer³

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…In this regard, advances in pulsed laser sources with a high peak field strength greatly accelerated the adoption of this technique. In the optical regime, besides direct measurement of SHG, the angular anisotropy of SHG is often used to characterize electronic and magnetic orders in solids, offering an ultra-sensitive probe of crystalline symmetry [3]. For example, SHG angular anisotropy has been used to characterize the symmetries of ferroic materials [4,5], multipolar order [6], and chiral structures [7,8].…”

mentioning

confidence: 99%

Polarization-Resolved Extreme Ultraviolet Second Harmonic Generation from LiNbO$_3$

Uzundal,

Jamnuch,

Berger

et al. 2021

Preprint

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Second harmonic generation (SHG) spectroscopy ubiquitously enables the investigation of surface chemistry, interfacial chemistry as well as symmetry properties in solids. Polarization-resolved SHG spectroscopy in the visible to infrared regime is regularly used to investigate electronic and magnetic orders through their angular anisotropies within the crystal structure. However, the increasing complexity of novel materials and emerging phenomena hamper the interpretation of experiments solely based on the investigation of hybridized valence states. Here, polarizationresolved SHG in the extreme ultraviolet (XUV-SHG) is demonstrated for the first time, enabling element-resolved angular anisotropy investigations. In non-centrosymmetric LiNbO 3 , elemental contributions by lithium and niobium are clearly distinguished by energy dependent XUV-SHG measurements. This element-resolved and symmetry-sensitive experiment suggests that the displacement of Li ions in LiNbO 3 , which is known to lead to ferroelectricity, is accompanied by distortions to the Nb ion environment that breaks the inversion symmetry of the NbO 6 octahedron as well. Our simulations show that the measured second harmonic spectrum is consistent with Li ion displacements from the centrosymmetric position by ∼0.5 A while the Nb-O bonds are elongated/contracted by displacements of the O atoms by ∼0.1 A. In addition, the polarizationresolved measurement of XUV-SHG shows excellent agreement with numerical predictions based on dipole-induced SHG commonly used in the optical wavelengths. This constitutes the first verification of the dipole-based SHG model in the XUV regime. The findings of this work pave the way for future angle and time-resolved XUV-SHG studies with elemental specificity in condensed matter systems.

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Ultrafast terahertz emission from emerging symmetry-broken materials

et al. 2023

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Nonlinear optical spectroscopies are powerful tools for investigating both static material properties and light-induced dynamics. Terahertz (THz) emission spectroscopy has emerged in the past several decades as a versatile method for directly tracking the ultrafast evolution of physical properties, quasiparticle distributions, and order parameters within bulk materials and nanoscale interfaces. Ultrafast optically-induced THz radiation is often analyzed mechanistically in terms of relative contributions from nonlinear polarization, magnetization, and various transient free charge currents. While this offers material-specific insights, more fundamental symmetry considerations enable the generalization of measured nonlinear tensors to much broader classes of systems. We thus frame the present discussion in terms of underlying broken symmetries, which enable THz emission by defining a system directionality in space and/or time, as well as more detailed point group symmetries that determine the nonlinear response tensors. Within this framework, we survey a selection of recent studies that utilize THz emission spectroscopy to uncover basic properties and complex behaviors of emerging materials, including strongly correlated, magnetic, multiferroic, and topological systems. We then turn to low-dimensional systems to explore the role of designer nanoscale structuring and corresponding symmetries that enable or enhance THz emission. This serves as a promising route for probing nanoscale physics and ultrafast light-matter interactions, as well as facilitating advances in integrated THz systems. Furthermore, the interplay between intrinsic and extrinsic material symmetries, in addition to hybrid structuring, may stimulate the discovery of exotic properties and phenomena beyond existing material paradigms.

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Rotational Anisotropy Nonlinear Harmonic Generation

Cited by 7 publications

References 213 publications

Photocurrent-driven transient symmetry breaking in the Weyl semimetal TaAs

Photocurrent-driven transient symmetry breaking in the Weyl semimetal TaAs

Polarization-Resolved Extreme Ultraviolet Second Harmonic Generation from LiNbO$_3$

Ultrafast terahertz emission from emerging symmetry-broken materials

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