One-dimensional Interacting Electron System Research Articles

Igor Dzyaloshinskii’s contribution to our understanding of the physics of one-dimensional interacting electron systems

Among his many important contributions to condensed matter physics, Igor Dzyaloshinskii published several seminal papers which contributed essentially to our understanding of the unusual behaviour of one-dimensional electronic systems. In this review I will briefly outline the main results obtained mostly in two of them and will present further developments in this field.

Effects of finite-range interactions on the one-electron spectral properties of one-dimensional metals: Application to Bi/InSb(001)

We study the one-electron spectral properties of one-dimensional interacting electron systems in which the interactions have finite range. We employ a mobile quantum impurity scheme that describes the interactions of the fractionalized excitations at energies above the standard Tomonga-Luttinger liquid limit and show that the phase shifts induced by the impurity describe universal properties of the one-particle spectral function. We find the explicit forms in terms of these phase shifts for the momentum dependent exponents that control the behavior of the spectral function near and at the (k,omega)-plane singularities where most of the spectral weight is located. The universality arises because the line shape near the singularities is independent of the short-distance part of the interaction potentials. For the class of potentials considered here, the charge fractionalized particles have screened Coulomb interactions that decay with a power-law exponent l>5. We apply the theory to the angle-resolved photo-electron spectroscopy (ARPES) in the highly one-dimensional bismuth-induced anisotropic structure on indium antimonide Bi/InSb(001). Our theoretical predictions agree quantitatively with both (i) the experimental value found in Bi/InSb(001) for the exponent alpha that controls the suppression of the density of states at very small excitation energy omega and (ii) the location in the (k,omega) plane of the experimentally observed high-energy peaks in the ARPES momentum and energy distributions. We conclude with a discussion of experimental properties beyond the range of our present theoretical framework and further open questions regarding the one-electron spectral properties of Bi/InSb(001).

A low-energy physics of an extended Hubbard chain with additional three-body couplings

A low-energy physics of a one-dimensional interacting electron system at half filling is constructed. Beyond the usual two-body approximation, the two different types of three-body couplings are highlighted. The rich ground-state phase diagrams are obtained at weak coupling. In the case of two-body repulsions, the off-diagonal three-body coupling favors the bond-located density-wave insulating phases, while the diagonal three-body attraction favors the superconducting phases.

Drude weight fluctuations in many-body localized systems

We numerically investigate the distribution of Drude weights $D$ of many-body states in disordered one-dimensional interacting electron systems across the transition to a many-body localized phase. Drude weights are proportional to the spectral curvatures induced by magnetic fluxes in mesoscopic rings. They offer a method to relate the transition to the many-body localized phase to transport properties. In the delocalized regime, we find that the Drude weight distribution at a fixed disorder configuration agrees well with the random-matrix-theory prediction $P(D) \propto (\gamma^2+D^2)^{-3/2}$, although the distribution width $\gamma$ strongly fluctuates between disorder realizations. A crossover is observed towards a distribution with different large-$D$ asymptotics deep in the many-body localized phase, which however differs from the commonly expected Cauchy distribution. We show that the average distribution width $\langle \gamma\rangle $, rescaled by $L\Delta$, $\Delta$ being the average level spacing in the middle of the spectrum and $L$ the systems size, is an efficient probe of the many-body localization transition, as it increases/vanishes exponentially in the delocalized/localized phase.

U(1) chiral symmetry in a one-dimensional interacting electron system with spin

We study a spin dependent Tomonaga-Luttinger model in one dimension, which describes electron transport through a single barrier. Using the Fermi-Bose equivalence in one dimension, we map the model onto a massless Thirring model with a boundary interaction. A field theoretical perturbation theory for the model has been developed and the chiral symmetry is found to play an important role. The classical bulk action possesses a global $U_A(1)^4$ chiral symmetry, since the fermion fields are massless. This global chiral symmetry is broken by the boundary interaction and the bosonic degrees of freedom, corresponding to the chiral phase transformation, become dynamical. They acquire an additional kinetic action from the fermion path integral measure and govern the critical behaviors of physical operators. On the critical line where the boundary interaction becomes marginal, they decouple from the fermi fields. Consequently the action reduces to the free field action, which contains only a fermion bilinear boundary mass term as an interaction term. By a renormalization group analysis, we obtain a new critical line, which differs from the previously known critical lines in the literature. The result of this work implies that the phase diagram of the one dimensional electron system may have a richer structure than previously known.

Nonlocal damping of helimagnets in one-dimensional interacting electron systems

We investigate the magnetization relaxation of a one-dimensional helimagnetic system coupled to interacting itinerant electrons. The relaxation is assumed to result from the emission of plasmons, the elementary excitations of the one-dimensional interacting electron system, caused by slow changes of the magnetization profile. This dissipation mechanism leads to a highly nonlocal form of magnetization damping that is strongly dependent on the electron-electron interaction. Forward scattering processes lead to a spatially constant damping kernel, while backscattering processes produce a spatially oscillating contribution. Due to the nonlocal damping, the thermal fluctuations become spatially correlated over the entire system. We estimate the characteristic magnetization relaxation times for magnetic quantum wires and nuclear helimagnets.

Influence of the modulated hopping on the one-dimensional interacting electron system

By introducing a modulation parameter (ξ), we study the one-dimensional correlated system with modulated hopping, on-site (U) and nearest-neighbor (V) repulsions in the weak-coupling regime. The induced three-body attraction changes topology of the conventional phase diagram. Besides the usual CDW and SDW phases, a BSDW phase exists for |U−2V|<8tξ2/π. In the absence of V, an insulator–metal transition takes place, and the TS phase is realized for ξ>πU/8t. Phenomenologically, the general quantum phase diagram including insulating and superconducting phases is discussed.

Effect of Intersite Repulsions on Magnetic Susceptibility of One-Dimensional Electron Systems at Quarter Filling

The temperature dependence of the magnetic susceptibility, \chi (T), is investigated for one-dimensional interacting electron systems at quarter-filling within the Kadanoff-Wilson renormalization-group method. The forward scattering on the same branch (the g_4-process) is examined together with the backward (g_1) and forward (g_2) scattering amplitudes on opposite branches. In connection with lattice models, we show that \chi (T) is strongly enhanced by the nearest-neighbor interaction, an enhancement that surpasses one of the next-nearest-neighbor interaction. A connection between our predictions for \chi (T) and experimental results for \chi (T) in quasi-one-dimensional organic conductors is presented.

Renormalization of impurity scattering in one-dimensional interacting electron systems in magnetic field

We study the renormalization of a single impurity potential in one-dimensional interacting electron systems in the presence of magnetic field. Using the bosonization technique and Bethe ansatz solutions, we determine the renormalization group flow diagram for the amplitudes of scattering of up- and down-spin electrons by the impurity in a quantum wire at low electron density and in the Hubbard model at less than half filling. In the absence of magnetic field the repulsive interactions are known to enhance backscattering and make the impurity potential impenetrable in the low-energy limit. On the contrary, we show that in a strong magnetic field the interaction may suppress the backscattering of majority-spin electrons by the impurity potential in the vicinity of the weak-potential fixed point. This implies that in a certain temperature range the impurity becomes almost transparent for the majority-spin electrons while it is impenetrable for the minority-spin ones. The impurity potential can thus have a strong spin-filtering effect.

Persistent currents in mesoscopic rings: A numerical and renormalization group study

The persistent current in a lattice model of a one-dimensional interacting electron system is systematically studied using a complex version of the density matrix renormalization group algorithm and the functional renormalization group method. We mainly focus on the situation where a single impurity is included in the ring penetrated by a magnetic flux. Due to the interplay of the electron-electron interaction and the impurity the persistent current in a system of N lattice sites vanishes faster then 1/N. Only for very large systems and large impurities our results are consistent with the bosonization prediction obtained for an effective field theory. The results from the density matrix renormalization group and the functional renormalization group agree well for interactions as large as the band width, even though as an approximation in the latter method the flow of the two-particle vertex is neglected. This confirms that the functional renormalization group method is a very powerful tool to investigate correlated electron systems. The method will become very useful for the theoretical description of the electronic properties of small conducting ring molecules.

Evidence for spin-charge separation in quasi-one-dimensional organic conductors.

Interacting conduction electrons are usually described within Fermi-liquid theory, which states that, in spite of strong interactions, the low-energy excitations are electron-like quasiparticles with charge and spin. In recent years there has been tremendous interest in conducting systems that are not Fermi liquids, motivated by the observation of highly anomalous metallic states in various materials, most notably the copper oxide superconductors. Non-Fermi-liquid behaviour is generic to one-dimensional interacting electron systems, which are predicted to be Luttinger liquids. One of their key properties is spin-charge separation: instead of quasiparticles, collective excitations of charge (with no spin) and spin (with no charge) are formed, which move independently and at different velocities. However, experimental confirmation of spin-charge separation remains a challenge. Here we report experiments probing the charge and heat current in quasi-one-dimensional conductors--the organic Bechgaard salts. It was found that the charge and spin excitations have distinctly different thermal conductivities, which gives strong evidence for spin-charge separation. The spin excitations have a much larger thermal conductivity than the charge excitations, which indicates that the coupling of the charge excitations to the lattice is important.

Multiparticle effects in nonequilibrium electron tunneling and field emission

We investigate energy resolved electric current from various correlated host materials under out-of-equilibrium conditions. We find that, due to a combined effect of electron-electron interactions, non-equilibrium and multi-particle tunnelling, the energy resolved current is finite even above the Fermi edge of the host material. In most cases, the current density possesses a singularity at the Fermi level revealing novel manifestations of correlation effects in electron tunnelling. By means of the Keldysh non-equilibrium technique, the current density is calculated for one-dimensional interacting electron systems and for two-dimensional systems, both in the pure limit and in the presence of disorder. We then specialise to the field emission and provide a comprehensive theoretical study of this effect in carbon nanotubes.

Microscopic model of superconductivity in carbon nanotubes.

We propose the model of a manifold of one-dimensional interacting electron systems to account for the superconductivity observed in ropes of nanotubes. We rely on the strong suppression of single-particle hopping between neighboring nanotubes in a disordered rope and conclude that the tunneling takes place in pairs of electrons, which are formed within each nanotube due to the existence of large superconducting correlations. Our estimate of the transition temperature is consistent with the values that have been measured experimentally in ropes with about 100 metallic nanotubes.

Unified theory for photoemission and light absorption spectra of a one-dimensional interacting electron system

Very recently, the angle-resolved photoemission spectrum (ARPES) of $[\mathrm{Ni}(\mathrm{chxn}{)}_{2}\mathrm{Br}]{\mathrm{Br}}_{2}$ $(\mathrm{chxn}=1R,$ $2R$-cyclohexanediamine), which is a one-dimensional insulator driven by the strong Coulomb repulsion, has been experimentally observed. The experiment has clearly shown that a one-body gap appearing in the ARPES is much smaller than an optical gap observed in the light-absorption spectrum (LAS). The apparent difference between these two gaps indicates the breakdown of a mean-field description of this strongly correlated electron system. In this paper, we show that the ARPES and LAS of $[\mathrm{Ni}(\mathrm{chxn}{)}_{2}\mathrm{Br}]{\mathrm{Br}}_{2}$ are consistently explained within the framework of the one-dimensional extended Hubbard model. Lehmann spectra of the one-body and light-absorption-type two-body Green functions are calculated by a quantum Monte Carlo method. Our numerical results reproduce the experimentally observed ARPES and LAS, confirming the small one-body gap and large optical gap. The apparent difference in the gap structures can be explained by a dynamical Zeeman field induced by quantum fluctuations.

Effects of Next-Nearest-Neighbor Repulsion on One-Dimensional Quarter-Filled Electron Systems

We examine effects of the next-nearest-neighbor repulsion on electronic states of a one-dimensional interacting electron system which consists of quarter-filled band and interactions of on-site and nearest-neighbor repulsion. We derive the effective Hamiltonian for the electrons around wave number ± k F ( k F : Fermi wave number) and apply the renormalization group method to the bosonized Hamiltonian. It is shown that the next-nearest-neighbor repulsion makes 4 k F -charge ordering unstable and suppresses the spin fluctuation. Further the excitation gaps and spin susceptibility are also evaluated.

Effect of the long-range random potential on optical conductivity in a one-dimensional extended-Fermi-surface system

We study the effect of the long-range random potential on optical conductivity in a one-dimensional interacting electron system with extended-Fermi surface. We apply Abelian bosonization to show that in one part of the momentum space the system has a metallic behavior with a gap in the spin sector, while in the other region of momentum space it behaves like a gapless Luttinger liquid (paramagnetic metallic phase). Consequently we consider the scattering of electrons with the long-range random potential (forward scattering disorder) in that region of momentum space, where the system is in gapless Luttinger liquid phase. The real part of the optical conductivity has no Drude peak for small frequency $(\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\omega}}0),$ but the Drude weight is nonzero and it has the doping dependence, while the imaginary part of the optical conductivity shows the usual $1/\ensuremath{\omega}$ behavior, like in the clean system, and it has no doping dependence. We explain the doping dependence with the help of one-dimensional exact density of states.

Commensurability in one-dimensional electron systems at quarter-filling

We examine the role of commensurability in electronic states and excitations for a one-dimensional interacting electron system at quarter-filling with on-site ( U), nearest-neighbor ( V 1) and next-nearest-neighbor ( V 2) repulsive interactions. By applying the renormalization group method to the bosonized model, it is shown that the next-nearest-neighbor repulsion stabilizes 2 k F density waves and induces the excitation gap in spin fluctuation for V 2> U/2.

Finite Temperature Correlation Functions of One-dimensional Interacting Electron Systems

The well-known bosonisation method of one-dimensional electron systems is extended to finite temperatures. As an example, the correlation functions of the non-interacting case are explicitly calculated. The presentation is pedagogical and is intended to be accessible to graduate students or physicists who are not experts in this field.

A Barrier Problem in Luttinger Liquid**The project supported by National Natural Science Foundation of China

By using Gaussian wave functional method, the problem of a single barrier in a one-dimensional interacting electron system is studied. We have constructed the ground state of the system and discussed the phase diagram at the weak barrier limit.

Spin and charge separation in a mesoscopic ring

Abstract We propose a simple model, i.e., a magnetic impurity embedded in a mesoscopic ring, which can be used to detect the spin and charge separation in a one-dimensional interacting electron system by measuring the basic period of the persistent current produced by the Aharonov-Bohm flux threading the ring and the low temperature behavior of the impurity susceptibility. The former only depends upon a dimensionless coupling strength parameter g which characterizes the interaction among the charge collective excitation modes, while the latter is completely controlled by another parameter g , which characterizes the interaction among the spin collective excitation modes.