Possible evidence of non-Fermi liquid behaviour from Quasi-one-dimensional indium nanowires

Abstract

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

Plasmons in nanoscale and atomic-scale systems

“…(Here, λ is the propagation wavelength of the plasmonic charge-density wave in the wire.) This was also observed in previous momentum-resolved EELS experiments [79,82,86]. For a finite wire with length L, plasmonic excitation with wavelength λ longer than 2L is not possible and the plasmon frequency remain the same as that for λ = 2L = 2π/q ; it forms a standing wave, enabling optical detection.…”

“…The observed feature is associated with low-energy plasmonic excitation in atomic wires [16,46,47,79,80,86]. For sufficiently long indium wires, the plasmon frequency undergoes a redshift as the plasmon wavelength λ increases or the plasmon momentum parallel to the wire axis q = π/λ decreases.…”

Evidence of metallic nature of the surface bands of Au/Si(557)

“…͑c͒ Corresponding change on the shoulder of Au 4f 7/2 peak. electron energy-loss spectroscopy study 15,33 as well as theoretical calculations 25 have shown the presence of a 1D plasmon excitation from this system with an excitation energy ranging from 0.8 to 1.0 eV, the satellite peak of the Au 4f 7/2 may reflect the plasmon excitation in the Au-Si metallic chains. This assignment becomes more plausible when one finds the remarkably weakened satellite when the surface becomes less metallic by contamination.…”

“…8,9 The Peierls instabilities characteristic of 1D metallic system has also been invoked to this 1D metallic system. 5,6,10,24,33 Ahn et al 10 reported, however, that only S1 is metallic at room temperature ͑RT͒, which undergoes a Peierls-type metal-insulator transition ͑MIT͒ with a transition temperature T c = 120 K while S2 appears to be nonmetallic with an energy gap of about 100 meV nearly independent of T. They also observed period doubling below T c for the step-edge Si atoms associated with the S1 band in their scanning tunneling microscope ͑STM͒ images. Meanwhile from their DFT calculations, Sánchez-Portal et al 9,18 showed that the splitting of a surface band into two S1 and S2 bands near E F stems from the spin-orbit coupling of the Si-Au band.…”

Synthesis of Indium Nanowires by Galvanic Displacement and Their Optical Properties

“…The past studies on the preparation of indium nanowires using thermal evaporation have revealed the interesting structural and electrical and optical properties of these samples [ 15 , 18 , 23 ]. Galvanic displacement or the so-called immersion plating is another way to synthesize nanoscale materials in recent years [ 24 ].…”