Electron correlation and many‐body effects at interfaces on semiconducting substrates

Abstract

Low dimensional systems are characterized by at least one spatial dimension of only some atoms. Such size reduction has often important consequences for physical properties. Electronic correlation and electron–phonon coupling can originate Mott insulators or charge density waves (CDWs), both phenomena enhanced by dimensionality reduction. Interfaces offer a natural way of reducing the dimensionality. Among all the surfaces, semiconducting surfaces are particularly well adapted for electronic correlation studies. In them, correlation is enhanced because of the low dimension, the electronic localization in dangling bonds and the large inter‐orbital distances in reconstructions. Despite these factors favoring correlation, eventually stronger than in bulk systems, the field is by far much less developed. We review here the discovery of correlated surfaces, while studying the Schottky barrier of alkalis on Si or GaAs, and coetaneous studies on SiC. We summarize then the studies on K/Si(111):B, whose ${\left( {\sqrt {3} \times \sqrt {3} } \right)}R30^\circ $ was considered a surface Mott insulator with an important electron‐phonon coupling. The recent discovery of a ${\left( {2\sqrt {3} \times 2\sqrt {3} } \right)}R30^\circ $ symmetry has been first interpreted as evidence of a bipolaronic insulator, but new findings have finally proven it to be a band insulator. We will then focus on the model system Sn/Ge(111). The last unclear issue about the (3 × 3) reconstruction at 150 K was related to the Sn 4d core level. High‐resolution photoemission has clarified the core level deconvolution while refining the structural model. This metallic reconstruction is sensitive to electronic correlations which trigger a phase transition to a Mott phase below 30 K.

Homogeneous and heterogeneous nucleations in the surface phase transition: Si(111)4 × 1-In

“…Over the past few decades, the observations of both structural and electronic transitions in a number of metal/semiconductor surfaces have renewed interest in the phase transitions in reduced dimensions [1][2][3][4][5][6][7][8]. A study of the phase transitions at the surfaces has fundamental importance in understanding novel physics, which is richer than in the bulk, because of the enhanced electronic correlation and electron-phonon coupling [9]. A Si(111)-In surface composed of an array of indium atomic chains is a prototypical example undergoing a symmetry-breaking (4 × 1-to-8 × 2) structural phase transition, accompanied by a metalinsulator transition at approximately 120-130 K [3].…”

Cooperative interplay between impurities and charge density wave in the phase transition of atomic wires

“…One speculative possibility is that the D 2 defect is a time-averaged structure of the fluctuating D a between D a,L and D a,R (i.e., I e1 and I e2 in figure 5). 5 This temperature corresponds to the T c of the Si(111)-In surface with 1.0 L of oxygen, which is higher by about 7 K compared with the T c of the pristine surface determined in the similar procedure. This confirms the previously reported increase of the T c due to the O adsorption [26].…”

“…As the temperature decreased, the 8 × 2-LT area showed an abrupt increase occurring at approximately 133 K (which is higher than the T 125 c = K of pristine In wire), where the condensation of 2D CDW began 5 . The number of D a defects also increased at the expense of D 2 defects, whereas the total number of D a and D 2 V (filled state).…”

“…The former two properties emerge through phase transitions when the systems are sufficiently cooled. Over the past decades, the phase transitions in the reduced dimensional systems have been the subject of fundamental research to understand the novel physics, which is richer than in the bulk [4,5].…”

Ultrafast Atomic Diffusion Inducing a Reversible(23×23)R30°↔(Srour1, Trabada2, Martínez3 et al. 2015Phys. Rev. Lett.Self Cite7050View full textAdd to dashboardCite

“…Metallic overlayers on semiconductor surfaces are prone to phase transitions [1][2][3], and many exotic phenomena have been found in these two dimensional systems, such as low-dimensional superconductivity [4,5], magnetic orderings [6,7], and metal-insulator transitions [8][9][10][11][12][13][14][15][16][17]. In temperature-induced transitions, very often the dynamical fluctuation of surface atoms is associated with changes of the structural and/or electronic properties of the system.…”