Writing and erasing topological defects in charge density wave materials with femtosecond laser pulses

AbstractNonequilibrium phase transitions play a pivotal role in broad physical contexts, from condensed matter to cosmology. Tracking the formation of nonequilibrium phases in condensed matter requires a resolution of the long-range cooperativity on ultra-short timescales. Here, we study the spontaneous transformation of a charge-density wave in CeTe3 from a stripe order into a bi-directional state inaccessible thermodynamically but is induced by intense laser pulses. With ≈100 fs resolution coherent electron diffraction, we capture the entire course of this transformation and show self-organization that defines a nonthermal critical point, unveiling the nonequilibrium energy landscape. We discuss the generation of instabilities by a swift interaction quench that changes the system symmetry preference, and the phase ordering dynamics orchestrated over a nonadiabatic timescale to allow new order parameter fluctuations to gain long-range correlations. Remarkably, the subsequent thermalization locks the remnants of the transient order into longer-lived topological defects for more than 2 ns.

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Spectral flow and gauge invariance of the effective field theory of charge density wave with topological defects

Quantum Coherence and Decoherence ◽

10.1016/b978-044450091-5/50060-9 ◽

1999 ◽

pp. 273-276

Author(s):

M. Hayashi

Keyword(s):

Field Theory ◽

Charge Density ◽

Effective Field Theory ◽

Gauge Invariance ◽

Charge Density Wave ◽

Density Wave ◽

Topological Defects ◽

Effective Field ◽

Spectral Flow

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Incommensurate modulated phases of the NbxTa1-xTe4 charge density wave system

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100120692 ◽

1992 ◽

Vol 50 (1) ◽

pp. 58-59

Author(s):

S. Ritchie ◽

J. C. Bennett ◽

A. Prodan ◽

F.W. Boswell ◽

J.M. Corbett

Keyword(s):

Charge Density ◽

Charge Density Wave ◽

Direct Evidence ◽

Density Wave ◽

Wave System ◽

Modulated Phases ◽

Metal Atoms ◽

Incommensurate Modulation ◽

End Members ◽

Modulation Wave Vector

A continuous sequence of compounds having composition NbxTa1-xTe4; 0 ≤ x ≤ 1 have been studied by electron diffraction and microscopy. Previous studies have shown that the end members of the series, TaTε4 and NbTε4 possess a quasi-one-dimensional character and exhibit charge density wave (CDW) distortions. In these compounds, the subcell structure is tetragonal with axes (a × a × c) and consists of the metal atoms (Nb or Ta) centered within an extended antiprismatic cage of Te atoms. At room temperature, TaTε4 has a commensurate modulation structure with a 2a × 2a × 3c unit cell. In NbTε4, an incommensurate modulation with × ∼ 16c axes is observed. Preliminary studies of the mixed compounds NbxTα1-xTε4 showed a discontinuous jump of the modulation wave vector commensurate to incommensurate when the Nb dopant concentration x, exceeded x ≃ 0.3, In this paper, the nature of the compositional dependence of is studied in greater detail and evidence is presented for a stepwise variation of . This constitutes the first direct evidence for a Devil's staircase in CDW materials.

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