Hidden CDW states and insulator-to-metal transition after a pulsed femtosecond laser excitation in layered chalcogenide 1T-TaS
 
 2−
 
 x
 
 
 Se
 
 
 x

Sun, Kai; Sun, Shuaishuai; Zhu, Chunhui; Tian, Huanfang; Yang, H. X.; Li, Jianqi

doi:10.1126/sciadv.aas9660

Cited by 50 publications

(21 citation statements)

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“…Recently, scanning tunnelling measurements in two-dimensional metallic dichalcogenides (TMDs) have revealed irregular charge ordered textures-nanoscale mosaics of charge-ordered domains separated by domain walls (DWs) which could be created and manipulated by light or by charge injection [1][2][3][4][5][6][7]. States created through non-equilibrium methods are of particular interest for ultrafast memory devices [5,[8][9][10][11][12][13][14][15], but the mesoscopic metastability associated with these phenomena is not easily explained with conventional charge density wave (CDW) theory.…”

Section: Introductionmentioning

confidence: 99%

Configurational electronic states in layered transition metal dichalcogenides

et al. 2019

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Mesoscopic irregularly ordered and even amorphous self-assembled electronic structures were recently reported in two-dimensional metallic dichalcogenides (TMDs), created and manipulated with short light pulses or by charge injection. Apart from promising new all-electronic memory devices, such states are of great fundamental importance, since such aperiodic states cannot be described in terms of conventional charge-density-wave (CDW) physics. In this paper, we address the problem of metastable mesoscopic configurational charge ordering in TMDs with a sparsely filled charged lattice gas model in which electrons are subject only to screened Coulomb repulsion. The model correctly predicts commensurate CDW states corresponding to different TMDs at magic filling fractions = / / / / / f 1 3, 1 4, 1 9, 1 13, 1 16.mDoping away from f m results either in multiple neardegenerate configurational states, or an amorphous state at the correct density observed by scanning tunnelling microscopy. Quantum fluctuations between degenerate states predict a quantum charge liquid at low temperatures, revealing a new generalized viewpoint on both regular, irregular and amorphous charge ordering in transition metal dichalcogenides.

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Section: Introductionmentioning

confidence: 99%

Configurational electronic states in layered transition metal dichalcogenides

et al. 2019

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“…The discovery of new phases of matter has a long history of providing enhanced functionality, for example, for phase change memories. Moreover, the critical need for faster, smaller, and more energy-efficient nanotechnologies means that metastable phases of matter are a new frontier for functional materials ( 1 – 10 ). Correlated materials exhibit rich phase diagrams due to the coupling of charge, lattice, spin, and orbital degrees of freedom.…”

Section: Introductionmentioning

confidence: 99%

“…Because of the complexity of these interactions, the nature and origin of different phases and their transitions in strongly correlated materials are still under debate. In addition, the potential presence of metastable phases in many of these materials [e.g., the hidden state in 1 T -TaS 2 ( 4 , 6 , 10 )] has been a topic of great interest. However, methods to prepare, detect, and study metastable states are still under development.…”

Section: Introductionmentioning

confidence: 99%

Ultrafast electron calorimetry uncovers a new long-lived metastable state in 1 T -TaSe ₂ mediated by mode-selective electron-phonon coupling

et al. 2019

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Quantum materials represent one of the most promising frontiers in the quest for faster, lightweight, energy-efficient technologies. However, their inherent complexity and rich phase landscape make them challenging to understand or manipulate. Here, we present a new ultrafast electron calorimetry technique that can systematically uncover new phases of quantum matter. Using time- and angle-resolved photoemission spectroscopy, we measure the dynamic electron temperature, band structure, and heat capacity. This approach allows us to uncover a new long-lived metastable state in the charge density wave material 1T-TaSe2, which is distinct from all the known equilibrium phases: It is characterized by a substantially reduced effective total heat capacity that is only 30% of the normal value, because of selective electron-phonon coupling to a subset of phonon modes. As a result, less energy is required to melt the charge order and transform the state of the material than under thermal equilibrium conditions.

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“…-The general requirement for material realizations of monopole CDW states is the presence of nested Fermi surfaces enclosing Weyl points of the same chirality, which can occur in either an inversion-breaking or, as in this work, a time-reversalbreaking Weyl semimetal. In addition to the intrinsic ordering mechanism, CDW states can also be driven by an ultra-fast laser pulse, as demonstrated in a layered chalcogenide system [52]. If the CDW state instead occurs between Fermi surfaces enclosing Weyl points of opposite chiralities, the gap function has zero Berry phase and can either be fully gapped or develop nodes.…”

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confidence: 99%

Monopole charge density wave states in Weyl semimetals

Bobrow

Sun

2020

Phys. Rev. Research

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We study a new class of topological charge density wave states exhibiting monopole harmonic symmetries. The density-wave ordering is equivalent to pairing in the particle-hole channel due to Fermi surface nesting under interactions. When electron and hole Fermi surfaces carry different Chern numbers, the particle-hole pairing exhibits a non-trivial Berry phase inherited from band structure topology independent of concrete density-wave ordering mechanism. The associated density-wave gap functions become nodal, and the net nodal vorticity is determined by the monopole charge of the pairing Berry phase. The gap function nodes become zero-energy Weyl nodes of the bulk spectra of quasi-particle excitations. These states can occur in doped Weyl semimetals with nested electron and hole Fermi surfaces enclosing Weyl nodes of the same chirality in the weak coupling regime. Topologically non-trivial low-energy Fermi arc surface states appear in the density-wave ordering state as a consequence of the emergent zero-energy Weyl nodes.

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Hidden CDW states and insulator-to-metal transition after a pulsed femtosecond laser excitation in layered chalcogenide 1T-TaS _{2−

_x} Se _{_x}

Abstract: Ultrafast laser excitation of electronic crystals reveals hidden quantum states with new polaron cluster ordering.

Cited by 50 publications

References 34 publications

Configurational electronic states in layered transition metal dichalcogenides

Configurational electronic states in layered transition metal dichalcogenides

Ultrafast electron calorimetry uncovers a new long-lived metastable state in 1 T -TaSe ₂ mediated by mode-selective electron-phonon coupling

Monopole charge density wave states in Weyl semimetals

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Hidden CDW states and insulator-to-metal transition after a pulsed femtosecond laser excitation in layered chalcogenide 1T-TaS 2− x Se x

Abstract: Ultrafast laser excitation of electronic crystals reveals hidden quantum states with new polaron cluster ordering.

Cited by 50 publications

References 34 publications

Configurational electronic states in layered transition metal dichalcogenides

Configurational electronic states in layered transition metal dichalcogenides

Ultrafast electron calorimetry uncovers a new long-lived metastable state in 1 T -TaSe 2 mediated by mode-selective electron-phonon coupling

Monopole charge density wave states in Weyl semimetals

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Product

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About

Hidden CDW states and insulator-to-metal transition after a pulsed femtosecond laser excitation in layered chalcogenide 1T-TaS _{2−

_x} Se _{_x}

Ultrafast electron calorimetry uncovers a new long-lived metastable state in 1 T -TaSe ₂ mediated by mode-selective electron-phonon coupling