Observation of the Polaronic Transition in a Two-Dimensional Electron System

Andrei, Eva Y.

doi:10.1103/physrevlett.52.1449

Cited by 74 publications

(20 citation statements)

References 13 publications

(7 reference statements)

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“…The first indication of this phenomenon was given by mobility measurements of electrons on relatively thick helium films ͑around 10 Ϫ4 cm) on a sapphire substrate. 2 Later, a similar behavior was observed in the mobility of electrons on very thin helium films ͑around 10 Ϫ6 cm) adsorbed on a quench-condensed solid hydrogen substrate. 3,4 However, so far it is not clear whether there is any correlation between the data of Refs.…”

supporting

confidence: 58%

“…However, the authors conclude that self-trapping of the electrons can not explain the dip behavior in Ref. 2, because in this case the self-trapping energy is too small with respect to the experimental temperature. Various experiments with electrons on helium films ͑see the review article by Dahm 6 ͒ show the monotonic decrease of electron mobility versus the coupling constant.…”

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confidence: 93%

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Dip problem of the electron mobility on a thin helium film

Shikin¹,

Klier

Doicescu

et al. 2001

Phys. Rev. B

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Electrons floating above liquid helium form an ideal two-dimensional system with an extremely high mobility. However, the mobility can change substantially when decreasing the thickness of the helium film from bulk to a thin film of a few hundred Å. Furthermore it is observed that for certain film thicknesses there is a pronounced dip in the mobility. We present theoretical investigations and measurements concerning this problem. Taking into account the roughness of the substrate, which supports the helium film, we find theoretically a discontinuity in the chemical potential of the electrons which results in a diplike behavior in the electron current and hence in the electron mobility. This scenario is supported by direct measurements of the electron current on substrates with different roughness and at different electron densities. A two-dimensional ͑2D͒ electron sheet, localized on the surface of a liquid helium film, forms a well-defined Coulomb system. The mobility of such a charge system strongly depends on the thickness of the helium film. Whereas on bulk helium the electron mobility can reach extremely high values up to 10 4 m 2 /V s, 1 for a thin van der Waals film the mobility can drastically decrease and usually depends on the surface quality of the underlying substrate.One of the qualitative questions in the 2D electron kinetics is the so-called dip problem in the electron mobility on a thin liquid helium film. The first indication of this phenomenon was given by mobility measurements of electrons on relatively thick helium films ͑around 10 Ϫ4 cm) on a sapphire substrate.2 Later, a similar behavior was observed in the mobility of electrons on very thin helium films ͑around 10 Ϫ6 cm) adsorbed on a quench-condensed solid hydrogen substrate.3,4 However, so far it is not clear whether there is any correlation between the data of Refs. 2 and Refs. 3,4.There exist several interpretations for the dip effect. In a paper by Peeters and Jackson 5 the electron mobility on helium films above a flat substrate is calculated. It predicts the monotonic mobility decrease versus the coupling constant, which is sensitive to the helium film thickness, and the nonmonotonic mobility behavior due to the self-trapping effect. However, the authors conclude that self-trapping of the electrons can not explain the dip behavior in Ref. 2, because in this case the self-trapping energy is too small with respect to the experimental temperature. Various experiments with electrons on helium films ͑see the review article by Dahm 6 ͒ show the monotonic decrease of electron mobility versus the coupling constant. But there is no indication of the dip effect, which should be more probable in the self-trapping scenario, 5 when the helium film thickness becomes small enough.The second interpretation for the dip effect is given for a nonflat substrate. As shown in Refs. 4 and 7 a diplike behavior of the electron mobility versus helium film thickness can develop in the presence of substrate corrugation. 8 Such a situation is only possible, if ...

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supporting

confidence: 58%

mentioning

confidence: 93%

Dip problem of the electron mobility on a thin helium film

Shikin¹,

Klier

Doicescu

et al. 2001

Phys. Rev. B

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“…We would like to add that we have no indication that for our system the high resistivity at small film thickness should be associated with the formation of a polaron state, as suggested for SSE on helium films above a sapphire substrate. 4 In this simple picture then the background resistivity Pz at Ta consists of the two contributions due to gas atom scattering (=pl) and scattering from surface roughness (=Oz-PO.…”

Section: Discussionmentioning

confidence: 99%

“…Experimental results will be presented in Sec. 4. Section 5 gives a discussion of our results in connection not only with PI's explanation, but also with a proposed polaron formation.…”

Section: Introductionmentioning

confidence: 99%

Surface state electrons on a hydrogen film. 2. Influence of adsorbed helium films

1991

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“…6 Even though the formation of the localized polaron state has been claimed, there is no conclusive interpretation about the origin of the mobility dip in some experiments and the question is still controversial. 7 Quite recently 1D confinement effects on surface electrons on bulk helium have been addressed by using the hydrodynamic model of the polaron which describes the energetics of the dimple formation on the surface of liquid helium and its transport properties. 8 Even though surface excitations of the liquid helium film have in general a complicated dispersion relation coming from contributions of surface tension, gravity and film thickness, in the case of thin films the ripplon spectrum has a well-defined acoustical character.…”

Section: Introductionmentioning

confidence: 99%

Polaron effects in electron channels on a helium film

et al. 2001

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Using the Feynman path-integral formalism we study the polaron effects in quantum wires above a liquid helium film. The electron interacts with two-dimensional (2D) surface phonons, i.e. ripplons, and is confined in one dimension (1D) by an harmonic potential. The obtained results are valid for arbitrary temperature (T ), electron-phonon coupling strength (α), and lateral confinement (ω0). Analytical and numerical results are obtained for limiting cases of T , α, and ω0. We found the surprising result that reducing the electron motion from 2D to quasi-1D makes the self-trapping transition more continuous. 63.20.Kr, 71.38.+i

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Observation of the Polaronic Transition in a Two-Dimensional Electron System

Cited by 74 publications

References 13 publications

Dip problem of the electron mobility on a thin helium film

Dip problem of the electron mobility on a thin helium film

Surface state electrons on a hydrogen film. 2. Influence of adsorbed helium films

Polaron effects in electron channels on a helium film

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