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Scanning tunnelling microscopy of 1‐D and 2‐D charge‐density wave systems
Author(s) -
Gammie G.,
Skala S.,
Hubacek J. S.,
Brockenbrough R.,
Lyons W. G.,
Tucker J. R.,
Lyding J. W.
Publication year - 1988
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1111/j.1365-2818.1988.tb01413.x
Subject(s) - charge density wave , condensed matter physics , quantum tunnelling , scanning tunneling microscope , lattice (music) , orthorhombic crystal system , commensurability (mathematics) , diffraction , physics , chemistry , optics , geometry , superconductivity , mathematics , acoustics
SUMMARY We have used a new variable temperature scanning tunnelling microscope (STM) to study quasi‐1D and 2‐D charge‐density wave (CDW) systems. The 1‐D systems, typified by NbSe 3 and TaS 3 , are of special interest since they exhibit unusual transport phenomena associated with moving CDW above a threshold electric field. In the case of NbSe 3 , room temperature STM images show both major and subtle details of the lattice structure. At present, however, images taken below the Peierls transition temperature of T P =144 K resolve major lattice details but are not sufficiently clear to resolve the CDW. On the other hand, for the fully gapped CDW system orthorhombic‐TaS 3 , the CDW modulation superimposed on the lattice structure and having the correct period of four times the S‐S spacing of 3·3 Å, is observed below T P =215 K. Above T P , the main observable feature is the S‐S spacing along the chains. STM measurements have also been performed on the 2‐D CDW system 1T‐TaS 2 in its incommensurate, nearly commensurate, fully commensurate and trigonal phases. For the nearly commensurate phase, STM images show uniform commensurability with a relatively low concentration of small, time‐varying discommensurations in contrast to models pradicting a regular domain structure. In the trigonal phase, however, evidence is seen for the striped phase composed of long, nearly parallel discommensurations.