We report possible evidence of non-Fermi liquid (NFL) observed at room temperature from the quasi one-dimensional (1D) indium (In) nanowires self-assembled on Si(111)-7×7 surface. Using high-resolution electron-energy-loss spectroscopy, we have measured energy and width dispersions of a low energy intrasubband plasmon excitation in the In nanowires.We observe the energy-momentum dispersion ω(q) in the low q limit exactly as predicted by both NFL theory and the random-phase-approximation. The unusual non-analytic width dispersion ζ(q) ∼ q α measured with an exponent α=1.40±0.24, however, is understood only by the NFL theory. Such an abnormal width dispersion of low energy excitations may probe the NFL feature of a non-ideal 1D interacting electron system despite the significantly suppressed spin-charge separation (≤40 meV). I. INTRODUCTIONSince the early prediction of non-Fermi liquid (NFL) behavior for an one-dimensional (1D) interacting electron system,[1] numerous efforts have been made to find evidence of NFL from various forms of 1D conductors including the earlier fractional quantum Hall system,[2] carbon nanotubes,[3] self-assembled nanowires on solid surfaces,[4-6] and anisotropic bulk materials.[7-10] The essential nature of NFL in the 1D electrons systems with enhanced electron correlations is the low energy bosonic collective excitations rather than the single-particle excitations in Fermi liquids.[11] Photoemission spectroscopy (PES) has been used most extensively to probe characteristic features of NFL such as the power law behaviors of spectral function near Fermi level,[3, 10] the spin-charge separation,[4, 7, 8] and the presence of pseudo-gap.[9] Since any deviation from an ideal 1D electrons system such as the presence of impurities, disorder, and thermal fluctuation may sensitively affect the dynamics of these collective excitations,[10-12] continued discussions have been made for some NFL systems claimed earlier.[4, 5] Although one expects infinite life time for such excitations in an ideal NFL, added interactions due to any deviations in real 1D systems may cause the damping of life time τ . Samokhin showed that the damped life time caused by collisions between the excitations due to the nonlinear band curvature even in a clean NFL system

We have investigated electronic and structural properties of thallium (Tl) nanoclusters formed on the Si(111)-7×7 surface at room temperature (RT) by utilizing photoemission spectroscopy (PES) and high-resolution electron-energy-loss spectroscopy (HREELS) combined with first principles calculations. Our PES data show that the state S2 stemming from Si restatoms remains quite inert with Tl coverage θ while S1 from Si adatoms gradually changes, in sharp contrast with the rapidly decaying states of Na or Li nanoclusters. No Tl-induced surface state is observed until θ=0.21 ML where Tl nanoclusters completely cover the faulted half unit cells (FHUCs) of the surface. These spectral behaviors of surface states and a unique loss peak L2 associated with Tl in HREELS spectra indicate no strong Si-Tl bonding and are well understood in terms of gradual filling of Si dangling bonds with increasing θ. Our calculational results further reveal that there are several metastable atomic structures for Tl nanoclusters at RT transforming from each other faster than 10 10 flippings per second. We thus conclude that the highly mobile Tl atoms form self-trapped nanoclusters within FHUC at RT with several metastable phases. The mobile and multi-phased nature of Tl nanoclusters not only account for all the existing experimental observations including the fuzzy scanning tunneling microscope images and a dynamical model proposed by recent x-ray study but also provides an example of self-trapping of atoms in a nanometer-scale region.