Visualization of Chiral Electronic Structure and Anomalous Optical Response in a Material with Chiral Charge Density Waves

Yang, Huaixin; He, Kuanyu; Koo, Jahyun; Shen, Shiwei; Zhang, S. H.; Liu, Gao-Yong; Liu, Y. Z.; Chen, C.; Liang, Aiji; Huang, Kui; Wang, M. X.; Gao, Jun; Luo, Xinyao; Yang, L. X.; Sun, Ying; Yan, Shichao; Yan, Binhang; Chen, Y. L.; Xi, Xuekui; Liu, Z. K.

doi:10.1103/physrevlett.129.156401

Cited by 24 publications

(16 citation statements)

References 64 publications

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“…The out-of-plane A 1g Raman modes for the σ+σ+ and σ−σ− configurations are almost the same, whereas the intensities of in-plane E g modes differ remarkably for the σ+σ− and σ−σ+ configurations, indicating that the chiral Raman response may correspond to an in-plane chiral structure. Similar experimental results of chiral Raman response in 1T-TaS 2 have been reported recently, which were well explained by Raman tensor analysis, either by introducing an antisymmetric Raman tensor or including complex Raman tensor elements 28 , 29 .…”

Section: Resultssupporting

confidence: 88%

Spectroscopic visualization and phase manipulation of chiral charge density waves in 1T-TaS2

et al. 2023

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The chiral charge density wave is a many-body collective phenomenon in condensed matter that may play a role in unconventional superconductivity and topological physics. Two-dimensional chiral charge density waves provide the building blocks for the fabrication of various stacking structures and chiral homostructures, in which physical properties such as chiral currents and the anomalous Hall effect may emerge. Here, we demonstrate the phase manipulation of two-dimensional chiral charge density waves and the design of in-plane chiral homostructures in 1T-TaS2. We use chiral Raman spectroscopy to directly monitor the chirality switching of the charge density wave—revealing a temperature-mediated reversible chirality switching. We find that interlayer stacking favours homochirality configurations, which is confirmed by first-principles calculations. By exploiting the interlayer chirality-locking effect, we realise in-plane chiral homostructures in 1T-TaS2. Our results provide a versatile way to manipulate chiral collective phases by interlayer coupling in layered van der Waals semiconductors.

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Section: Resultssupporting

confidence: 88%

Spectroscopic visualization and phase manipulation of chiral charge density waves in 1T-TaS2

et al. 2023

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“…Figures 1b and 1c compare the Raman spectra I σ + σ − and I σ − σ + for two samples with opposite planar chirality, where σ i σ s (i, s = +, −) denotes helicities for the incident and scattered photons. Each sample shows nonzero differential spectra ∆I ≡ I σ + σ − − I σ − σ + in the CCDW and NCCDW phases for the E g phonons [36], whereas ∆I = 0 in the achiral ICCDW phase (Supplementary Fig. 1).…”

Section: Detection Of Ferro-rotational Ordermentioning

confidence: 99%

“…Planar chiral crystals are endowed with Raman tensors with off-diagonal components, giving rise to an interesting helicity-resolved Raman response that enables efficient discrimination of the two configurations [36]. Since ferro-rotational materials must also be planar chiral (Supplementary Note 1), this establishes helicity-resolved Raman scattering as a new probe of ferro-rotational order.…”

Section: Detection Of Ferro-rotational Ordermentioning

confidence: 99%

“…The circularly polarized measurements were performed by using a combination of two polarizers and one quarter-wave plate, as detailed in Ref. [36]. Specifically, the first polarizer and the quarter-wave plate set the helicity (σ + or σ − ) of the incident light.…”

Section: Raman Measurementsmentioning

confidence: 99%

“…The structure is planar chiral [18,31], breaking the vertical mirror symmetry that relates the two configurations. This peculiar feature, largely overlooked in the past decades, has come to the fore in the pursuit of chiral CDWs [32][33][34][35][36] and is susceptible to optical [31] or electrical [37] pulses. Recently, the planar-chiral phase was recognized to be ferro-rotational in nature [12], hosting two domain states corresponding to α and β.…”

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Electrical switching of ferro-rotational order in nano-thick 1T-TaS$_2$ crystals

Liu¹,

Qiu²,

He³

et al. 2022

Preprint

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Hysteretic switching of domain states is a salient character of all ferroic materials and the foundation for their multifunctional applications. Ferro-rotational order is emerging as a new type of ferroic order featuring structural rotations, but its controlled switching remains elusive due to its invariance under both time reversal and spatial inversion. Here, we demonstrate electrical switching of ferro-rotational domain states in nanometer-thick 1T -TaS 2 crystals in its charge-density-wave phases. Cooling from the high-symmetry phase to the ferrorotational phase under an external electric field induces domain state switching and domain wall formation, realized in a simple two-terminal configuration using a volt-scale voltage. Although the electric field does not couple with the order due to symmetry mismatch, it drives domain wall propagation to give rise to reversible, durable, and nonvolatile isothermal state switching at room temperature. These results pave the path for manipulation of the ferro-rotational order and its nanoelectronic applications. MainFerroic orders arise from symmetry-breaking phase transitions, finding applications in wide-ranging advanced technologies [1]. Symmetry therefore provides a powerful guide to the identification of conjugate fields that couple with and even switch the orders -a prerequisite for utilizing the associated multi-stable domain states [2]. This principle is well applicable to three out of the four types of ferroics with a vector order parameter [2]: ferromagnets (ferroelectrics) feature time-reversal (spatial-inversion) symmetry breaking spontaneous magnetization (electric polarization) that is switchable by a magnetic (electric) field, whereas the ferro-toroidal order breaks both symmetries and can be switched using composite magnetic and electric fields [3][4][5]. The remaining type -the ferro-rotational (also known as ferroaxial) order -stands out, as it is both time-reversal and spatial-inversion invariant, hence insensitive to electromagnetic fields [2,6]. The lack of external fields that hysteretically switch the ferro-rotational order casts doubts on its ferroic nature [7] and limits its potential applications.

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Recent Advances in Moiré Superlattice Systems by Angle‐Resolved Photoemission Spectroscopy

Li,

Wan,

2023

Advanced Materials

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The last decade has witnessed a flourish in two‐dimensional (2D) materials including graphene and transition metal dichalcogenides (TMDs) as atomic‐scale Legos. Artificial moiré superlattices via stacking 2D materials with a twist angle and/or a lattice mismatch have recently become a fertile playground exhibiting a plethora of emergent properties beyond their building blocks. These rich quantum phenomena stem from their nontrivial electronic structures that have been effectively tuned by the moiré periodicity. Modern angle‐resolved photoemission spectroscopy (ARPES) can directly visualize electronic structures with decent momentum, energy, and spatial resolution, thus could provide enlightening insights into fundamental physics in moiré superlattice systems and guides for designing novel devices. In this review, firstly a brief introduction is given on advanced ARPES techniques and basic ideas of band structures in a moiré superlattice system. Then ARPES research results of various moiré superlattice systems are highlighted, including graphene on substrates with small lattice mismatches, twisted graphene/TMD moiré systems, and high‐order moiré superlattice systems. Finally, we discuss on important questions that remain open, challenges in current experimental investigations and present an outlook on this field of research.This article is protected by copyright. All rights reserved

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Visualization of Chiral Electronic Structure and Anomalous Optical Response in a Material with Chiral Charge Density Waves

Cited by 24 publications

References 64 publications

Spectroscopic visualization and phase manipulation of chiral charge density waves in 1T-TaS2

Spectroscopic visualization and phase manipulation of chiral charge density waves in 1T-TaS2

Electrical switching of ferro-rotational order in nano-thick 1T-TaS$_2$ crystals

Recent Advances in Moiré Superlattice Systems by Angle‐Resolved Photoemission Spectroscopy

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