Evidence for a soft-phonon mechanism in the reconstruction of the Mo(001) surface

Hulpke, E.; Smilgies, Detlef‐M.

doi:10.1103/physrevb.40.1338

Cited by 47 publications

(38 citation statements)

References 21 publications

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“…Direct observation of the phonon softening at T > T c was done by means of inelastic He scattering [58][59][60][61]. The longitudinal surface phonon mode showed well-defined dispersion at T > 450 K, but exhibited considerable softening at ∼ 0.8M upon approaching T c , in qualitative agreement with the CDW scenario.…”

Section: Strong-coupling-cdw Picture For the Phase Transitions On W(0supporting

confidence: 58%

Surface Peierls transition on Cu(001) covered with heavier p-block metals

Aruga

2006

Surface Science Reports

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The Cu(001) surface covered with submonolayer coverages of In and Sn undergoes phase transitions at around 350-400 K. The transition is associated with the surface electronic structure change between low-temperature gapped and high-temperature ungapped ones. The energy gap positions in the k space coincide with the surface Brillouine zone boundaries of the low-temperature phases. These observations imply that the phase transitions are classified into the Peierls-type charge density wave (CDW) phase transition. The CDW ground states are characterized by large overall CDW gaps and long CDW correlation lengths. Structural studies show that the transitions are associated with order-disorder processes. This suggests that these are in strong-coupling regime. However, the associated gapped-ungapped change suggests that the electronic terms play significant role, in contradiction with the strong-coupling scenario. Based on the results of recent works on precise temperature dependence of the CDW gap and critical X-ray scattering, the origin of this dual nature and the detailed mechanism of the phase transition is discussed. It is suggested that the electronic entropy of the CDW ground state is not governed by the overall energy gap but by the gap between the upper band minimum and the Fermi level of the whole system. The dual nature of the surface Peierls transition on Cu(001) originates, on one hand, from the existence at metal surfaces of the two characteristic energy gaps: the overall gap, which determines the CDW stabilization energy, and the upper gap, which governs the electronic entropy. On the other hand, the CDW correlation length is suggested to play another significant role in determining the nature of the Peierls transition. The classification of the Peierls transisions according to the CDW correlation length and the gap size is discussed. It is suggested that the surface Peierls transition on metal-covered Cu(001) covered with heavier p-block metallic elements are qualitatively different from both the weak-coupling CDW transition, with long CDW correlation length and small gaps, and the strong-coupling CDW transitions, with short correlation lengths and large gaps, and should be classified into the third class, which is characterized by long coherence and strong coupling.

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Section: Strong-coupling-cdw Picture For the Phase Transitions On W(0supporting

confidence: 58%

Surface Peierls transition on Cu(001) covered with heavier p-block metals

Aruga

2006

Surface Science Reports

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“…[1][2][3][4][5][6][7][8][9][10][11] In addition to being easy to clean, Mo and W surfaces exhibit surface states, surface reconstructions, as well as interesting electronic and structural changes during chemisorption. They have thus been favorite platforms for studying surface phenomena for many decades.…”

Section: Introductionmentioning

confidence: 99%

“…While the tungsten surface in various orientations has been investigated extensively by both a variety of theoretical methods and surface techniques, comparatively less detailed information about the molybdenum surfaces is available. [1][2][3][4][5][6][7][8][9][10][11] In many respects, the structural properties of the molybdenum surface are similar to those of tungsten, but there are also subtle differences. For example, the clean ͑100͒ tungsten surface shows a (ͱ2ϫͱ2)R45°reconstruction, while more complex reconstructions of the clean Mo͑100͒ surface have been observed.…”

Section: Introductionmentioning

confidence: 99%

Surface atomic structures, surface energies, and equilibrium crystal shape of molybdenum

Chan

Jian

et al. 1998

Phys. Rev. B

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“…Some surfaces of molybdenum, in particular the (100) surface [1][2][3][4][5][6][7][8][9], are well known for surface reconstructions driven by Peierls-like instability [10][11][12] that originates from a charge density wave (CDW) driven transition coupling with the surface states at the Fermi level. The Peierls instability is induced by Fermi surface nesting (coincidence of the electronic states at the Fermi surface when shifted by the nesting wave vector q = 2k F , where k F is the Fermi wave vector) and is favored to occur in lowdimensional materials, anisotropic surfaces, and metals that have high densities of states at the Fermi level N(E F ).…”

Section: Introductionmentioning

confidence: 99%