Boundary Effects on Spectral Properties of Interacting Electrons in One Dimension

The single electron Green's function of the one-dimensional Tomonaga-Luttinger model in the presence of open boundaries is calculated with bosonization methods. We show that the critical exponents of the local spectral density and of the momentum distribution change in the presence of a boundary. The well understood universal bulk behavior always crosses over to a boundary dominated regime for small energies or small momenta. We show this crossover explicitly for the large-U Hubbard model in the low-temperature limit. Consequences for photoemission experiments are discussed.Comment: revised and reformatted paper to appear in Phys. Rev. Lett. (Feb. 1996). 5 pages (revtex) and 3 embedded figures (macro included). A complete postscript file is available from http://FY.CHALMERS.SE/~eggert/luttinger.ps or by request from [email protected]

Magnetoconductance oscillations in quasiballistic multimode nanowires

We calculate the conductance of quasi-one-dimensional nanowires with electronic states confined to a surface charge layer, in the presence of a uniform magnetic field. Two-terminal magnetoconductance (MC) between two leads deposited on the nanowire via tunnel barriers is dominated by density-of-states (DOS) singularities, when the leads are well apart. There is also a mesoscopic correction due to a higher-order coherent tunneling between the leads for small lead separation. The corresponding MC structure depends on the interference between electron propagation via different channels connecting the leads, which in the simplest case, for the magnetic field along the wire axis, can be crudely characterized by relative winding numbers of paths enclosing the magnetic flux. In general, the MC oscillations are aperiodic, due to the Zeeman splitting, field misalignment with the wire axis, and a finite extent of electron distribution across the wire cross section, and are affected by spin-orbit coupling. The quantum-interference MC traces contain a wealth of information about the electronic structure of multichannel wires, which would be complimentary to the DOS measurements. We propose a four-terminal configuration to enhance the relative contribution of the higher-order tunneling processes and apply our results to realistic InAs nanowires carrying several quantum channels in the surface charge-accumulation layer.Comment: 11 pages, 8 figure

Mechanism of CDW-SDW Transition in One Dimension

The phase transition between charge- and spin-density-wave (CDW, SDW) phases is studied in the one-dimensional extended Hubbard model at half-filling. We discuss whether the transition can be described by the Gaussian and the spin-gap transitions under charge-spin separation, or by a direct CDW-SDW transition. We determine these phase boundaries by level crossings of excitation spectra which are identified according to discrete symmetries of wave functions. We conclude that the Gaussian and the spin-gap transitions take place separately from weak- to intermediate-coupling region. This means that the third phase exists between the CDW and the SDW states. Our results are also consistent with those of the strong-coupling perturbative expansion and of the direct evaluation of order parameters.Comment: 5 pages(REVTeX), 5 figures(EPS), 1 table, also available from http://wwwsoc.nacsis.ac.jp/jps/jpsj/1999/p68a/p68a42/p68a42h/p68a42h.htm

Phase diagram of an asymmetric spin ladder

We investigate an asymmetric zig-zag spin ladder with different exchange integrals on both legs using bosonization and renormalization group. When the leg exchange integrals and frustration both are sufficiently small, renormalization group analysis shows that the Heisenberg critical point flows to an intermediate-coupling fixed point with gapless excitations and a vanishing spin velocity. When they are large, a spin gap opens and a dimer liquid is realized. Here, we find a continuous manifold of Hamiltonians with dimer product ground states, interpolating between the Majumdar-Ghosh and sawtooth spin-chain model.Comment: 4 pages, 2 EPS figures, to be published in PR

How universal is the one-particle Green's function of a Luttinger liquid?

The one-particle Green's function of the Tomonaga-Luttinger model for one-dimensional interacting Fermions is discussed. Far away from the origin of the plane of space-time coordinates the function falls off like a power law. The exponent depends on the direction within the plane. For a certain form of the interaction potential or within an approximated cut-off procedure the different exponents only depend on the strength of the interaction at zero momentum and can be expressed in terms of the Luttinger liquid parameters $K_{\rho}$ and $K_{\sigma}$ of the model at hand. For a more general interaction and directions which are determined by the charge velocity $v_{\rho}$ and spin velocity $v_{\sigma}$ the exponents also depend on the smoothness of the interaction at zero momentum and the asymptotic behavior of the Green's function is not given by the Luttinger liquid parameters alone. This shows that the physics of large space-time distances in Luttinger liquids is less universal than is widely believed.Comment: 5 pages with 2 figure

Spectral sum rules for the Tomonaga-Luttinger model

In connection with recent publications we discuss spectral sum rules for the Tomonaga-Luttinger model without using the explicit result for the one-electron Green's function. They are usefull in the interpretation of recent high resolution photoemission spectra of quasi-one-dimensional conductors. It is shown that the limit of infinite frequency and band cut\-off do not commute. Our result for arbitrary shape of the interaction potential generalizes an earlier discussion by Suzumura. A general analytical expression for the spectral function for wave vectors far from the Fermi wave vector $k_{F}$ is presented. Numerical spectra are shown to illustrate the sum rules.Comment: 9 pages, REVTEX 3.0, 2 figures added as postscript file

The spectral weight of the Hubbard model through cluster perturbation theory

We calculate the spectral weight of the one- and two-dimensional Hubbard models, by performing exact diagonalizations of finite clusters and treating inter-cluster hopping with perturbation theory. Even with relatively modest clusters (e.g. 12 sites), the spectra thus obtained give an accurate description of the exact results. Thus, spin-charge separation (i.e. an extended spectral weight bounded by singularities) is clearly recognized in the one-dimensional Hubbard model, and so is extended spectral weight in the two-dimensional Hubbard model.Comment: 4 pages, 5 figure

Interpretation of Photoemission Spectra of (TaSe4)2I as Evidence of Charge Density Wave Fluctuations

The competition between different and unusual effects in quasi-one-dimensional conductors makes the direct interpretation of experimental measurements of these materials both difficult and interesting. We consider evidence for the existence of large charge-density-wave fluctuations in the conducting phase of the Peierls insulator (TaSe4)2I, by comparing the predictions of a simple Lee, Rice and Anderson theory for such a system with recent angle-resolved photoemission spectra. The agreement obtained suggests that many of the unusual features of these spectra may be explained in this way. This view of the system is contrasted with the behaviour expected of a Luttinger liquid.Comment: Archive copy of published paper. 19 pages, 12 figures, uses IOP macro