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

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.

The Effects of Transition Metal Substitutions in the NbTe4-TaTe4 Charge-Density Wave System

1992 ◽  
Vol 45 (9) ◽  
pp. 1363 ◽  
Author(s):  
JC Bennett ◽  
FW Boswell ◽  
A Prodan ◽  
JM Corbett ◽  
S Ritchie
Keyword(s):  
Transition Metal ◽  
Charge Density ◽  
Charge Density Wave ◽  
Room Temperature ◽  
Density Wave ◽  
Dark Field ◽  
Wave System ◽  
Incommensurate Modulation ◽  
High Concentrations ◽  
A Charge

At room temperature, the structures of TaTe4 and NbTe4 are modulated by the presence of a charge-density wave which in the former compound is commensurate with the parent lattice and in the latter incommensurate. In addition, a series of incommensurate mixed crystals ( Tal-xNbx )Te4 (0 ≤ x ≤) exist in which the modulation wavevector increases as a function of x. In this paper, we report the occurrence of a systematic variation in the period of the charge-density wave upon substitution of the transition metal elements Ti, Zr or V for either Nb or Ta. Electron diffraction experiments reveal that, in TaTe4, substitutions of Group 4 elements Ti and Zr result in an incommensurate modulation with a decrease in the modulation wavevector q. In NbTe4, substitutions of Ti or Zr also reduce q, in this case towards the commensurate value, and, at sufficiently high concentrations, a commensurate phase is stabilized at room temperature. Vanadium substitutions in NbTe4 result in a slight increase in q. Satellite dark-field images reveal the presence of defects in the modulation structures of the doped crystals. The above results are discussed in terms of the factors which determine the charge-density wave periodicity in the NbTe4-TaTe4 system.

Spectroscopic signatures of phase transitions in a charge-density-wave system: 1T-TaS2

1992 ◽  
Vol 46 (12) ◽  
pp. 7407-7412 ◽  
Author(s):  
B. Dardel ◽  
M. Grioni ◽  
D. Malterre ◽  
P. Weibel ◽  
Y. Baer ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Charge Density ◽  
Charge Density Wave ◽  
Density Wave ◽  
Wave System ◽  
A Charge ◽  
Spectroscopic Signatures

Temperature hysteresis in dielectric and transport properties of charge density wave system o-TaS3

2005 ◽  
Vol 131 ◽  
pp. 183-184
Author(s):  
D. Dominko ◽  
D. Starešinić ◽  
K. Biljaković ◽  
P. Lunkenheimer ◽  
A. Loidl
Keyword(s):  
Charge Density ◽  
Transport Properties ◽  
Charge Density Wave ◽  
Density Wave ◽  
Temperature Hysteresis ◽  
Wave System

scholarly journals Folded superstructure and degeneracy-enhanced band gap in the weak-coupling charge density wave system 2H−TaSe2

2018 ◽  
Vol 97 (11) ◽  
Author(s):  
Y. W. Li ◽  
J. Jiang ◽  
H. F. Yang ◽  
D. Prabhakaran ◽  
Z. K. Liu ◽  
...  
Keyword(s):  
Charge Density ◽  
Band Gap ◽  
Charge Density Wave ◽  
Weak Coupling ◽  
Density Wave ◽  
Wave System
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