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Competition between magnetism and superconductivity can lead to unconventional and topological superconductivity. However, the experimental confirmation of the presence of Majorana edge states and unconventional pairing currently poses a major challenge. Here we consider a two-dimensional lattice model for a superconductor with spin-orbit coupling and exchange coupling to randomly distributed magnetic impurities. Depending on parameters of the model, this system may display topologically trivial or nontrivial edge states. We map out the phase diagram by computing the Bott index, a topological invariant defined in real space. We then use machine learning (ML) algorithms to predict the Bott index from the local density of states (LDOS) at zero energy, obtaining high-accuracy results. We also train ML models to predict the amplitude of odd-frequency pairing in the anomalous Green's function at zero energy. Once the ML models are trained using the LDOS, which is experimentally accessible via scanning tunneling spectroscopy, our method could be applied to predict the number of Majorana edge states and to estimate the magnitude of odd-frequency pairing in real materials., Comment: 10 pages, 8 figures

We study the dynamics of hard-core bosons on ladders, in the presence of strong kinetic constrains akin to those of the Bariev model. We use a combination of analytical methods and numerical simulations to establish the phase diagram of the model. The model displays a paired Tomonaga-Luttinger liquid phase featuring an emergent dipole symmetry, which encodes the local pairing constraint into a global, non-local quantity. We scrutinize the effect of such emergent low-energy symmetry during quench dynamics including single particle defects. We observe that, despite being approximate, the dipole symmetry still leads to very slow relaxation dynamics, which we model via an effective field theory. The model we discuss is amenable to realization in both cold atoms in optical lattices and Rydberg atom arrays with dynamics taking place solely in the Rydberg manifold. We present a blueprint protocol to observe the effect of emergent dipole symmetry in such experimental platforms, combining adiabatic state preparation with quench dynamics., Comment: 29 pages, 12 figures

We investigate the generic transport in a one-dimensional strongly correlated fermionic chain beyond linear response. Starting from a Gaussian wave packet with positive momentum on top of the ground state, we find that the numerical time evolution splits the signal into at least three distinct fractional charges moving with different velocities. A fractional left-moving charge is expected from conventional Luttinger liquid theory, but for the prediction of the two separate right-moving packets the nonlinearity of the dispersion must also be taken into account. This out-of-equilibrium protocol therefore allows a direct measurement of nonlinear interaction parameters, which also govern threshold singularities of dynamic response functions. The nonlinear Luttinger Liquid theory also predicts the correct dynamics at low energies, where it agrees with the conventional Luttinger liquid. Moreover, at high energies, the wave packet dynamics reveals signatures of composite excitations containing two-particle bound states. Our results uncover a simple strategy to probe the nonlinear regime in time-resolved experiments in quantum wires and ultracold-atom platforms.

We predict a general local spin-flip transition mechanism caused by magnetic quantum impurities in (partially) polarized phases of quantum magnets in the absence of conservation laws. This transition arises when a magnon bound state crosses zero energy as function of the magnetic field. As application, we study 2D van der Waals magnets described by the Kitaev-Heisenberg honeycomb model which applies to the transition metal trihalides CrI$_3$ and $\alpha$-RuCl$_3$. We consider adatom and substitutional impurity positions, and show how spin-flip transitions can be detected in scanning tunneling spectroscopy., Comment: 13 pages, 7 figures

Fractonic matter can undergo unconventional phase transitions driven by the condensation of particles that move along subdimensional manifolds. We propose that this type of quantum critical point can be realized in a bilayer of crossed Rydberg chains. This system exhibits a transition between a disordered phase and a charge-density-wave phase with subextensive ground state degeneracy. We show that this transition is described by a stack of critical Ising conformal field theories that become decoupled in the low-energy limit due to emergent subsystem symmetries. We also analyze the transition using a Majorana mean-field approach for an effective lattice model, which confirms the picture of a fixed point of decoupled critical chains. We discuss the unusual scaling properties and derive anisotropic correlators that provide signatures of subdimensional criticality in this realistic setup., Comment: 11 pages, 5 figures, published version

We formulate a Majorana mean-field theory for the extended $JK\Gamma$ Kitaev model in a magnetic Zeeman field of arbitrary direction, and apply it for studying spatially inhomogeneous states harboring vortices. This mean-field theory is exact in the pure Kitaev limit and captures the essential physics throughout the Kitaev spin liquid phase. We determine the charge profile around vortices and the corresponding quadrupole tensor. The quadrupole-quadrupole interaction between distant vortices is shown to be either repulsive or attractive, depending on parameters. We predict that electrically biased scanning probe tips enable the creation of vortices at preselected positions. Our results open new perspectives for the electric manipulation of Ising anyons in Kitaev spin liquids., Comment: 15 pages, 12 figures

We use junctions of critical spin-1 chains as the basic elements to construct a honeycomb network that harbors a gapless chiral spin liquid phase. The low-energy modes are described by spin-1 Majorana fermions that form a two-dimensional Fermi surface when the interactions at the junctions are tuned to the vicinity of chiral fixed points with staggered chirality. We discuss the physical properties and the stability of this chiral spin liquid phase against perturbations from the point of view of the effective field theory for the network. We find clear connections with the excitation spectrum obtained in parton constructions on the kagome lattice., Comment: 11 pages, 6 figures

In an altermagnet, the symmetry that relates configurations with flipped magnetic moments is a rotation. This makes it qualitatively different from a ferromagnet, where no such symmetry exists, or a collinear antiferromagnet, where this symmetry is a lattice translation. In this paper, we investigate the impact of the crystalline environment, enabled by the spin-orbit coupling, on the magnetic and electronic properties of an altermagnet. We find that, because each component of the magnetization acquires its own angular dependence, the Zeeman splitting of the bands has symmetry-protected nodal lines residing on mirror planes of the crystal. Upon crossing the Fermi surface, these nodal lines give rise to pinch points that behave as single or double type-II Weyl nodes. We show that an external magnetic field perpendicular to these mirror planes can only move the nodal lines, such that a critical field value is necessary to collapse the nodes and make the Weyl pinch points annihilate. This unveils the topological nature of the transition from a nodal to a nodeless Zeeman splitting of the bands. We also classify the altermagnetic states of common crystallographic point groups in the presence of spin-orbit coupling, revealing that a broad family of magnetic orthorhombic perovskites can realize altermagnetism., Comment: revised manuscript accepted for publication as an Editors' Suggestion in PRB

We study an exactly solvable model with bond-directional quadrupolar and octupolar interactions between spin-orbital entangled $j_{\mathrm{eff}} = \frac{3}{2}$ moments on the honeycomb lattice. We show that this model features a multipolar spin liquid phase with gapless fermionic excitations. In the presence of perturbations that break time-reversal and rotation symmetries, we find Abelian and non-Abelian topological phases in which the Chern number evaluates to $0$, $\pm 1$, and $\pm 2$. We also investigate quantum phase transitions out of the multipolar spin liquid using a parton mean-field approach and orbital wave theory. In the regime of strong integrability-breaking interactions, the multipolar spin liquid gives way to ferroquadrupolar-vortex and antiferro-octupolar ordered phases that harbor a hidden spin-$\frac{1}{2}$ Kitaev spin liquid. Our work unveils mechanisms for unusual multipolar orders and quantum spin liquids in Mott insulators with strong spin-orbit coupling., Comment: 14 pages, 9 figures

We use a network of chiral junctions to construct a family of topological chiral spin liquids in two spatial dimensions. The chiral spin liquid phase harbors SU(2)$_k$ anyons, which stem from the underlying SU(2)$_k$ WZW models that describe the constituent spin chains of the network. The network exhibits quantized spin and thermal Hall conductances. We illustrate our construction by inspecting the topological properties of the SU(2)$_2$ model. We find that this model has emergent Ising anyons, with spinons acting as vortex excitations that bind Majorana zero modes. We also show that the ground state of this network is threefold degenerate on the torus, asserting its non-Abelian character. Our results shed new light on the stability of non-Abelian topological phases in artificial quantum materials., Comment: 24 pages, 4 figures

We study the real-time dynamics of the Kondo effect after a quantum quench in which a magnetic impurity is coupled to two metallic Hubbard chains. Using an effective field theory approach, we find that for noninteracting electrons the charge current across the impurity is given by a scaling function that involves the Kondo time. In the interacting case, we show that the Kondo time decreases with the strength of the repulsive interaction and the time dependence of the current reveals signatures of the Kondo effect in a Luttinger liquid. In addition, we verify that the relaxation of the impurity magnetization does not exhibit universal scaling behavior in the perturbative regime below the Kondo time. Our results highlight the role of nonequilibrium dynamics as a valuable tool in the study of quantum impurities in interacting systems.

We study the fracton phase described by the Chamon model in a manifold with a boundary. The new processes and excitations emerging at the boundary can be understood by means of a diagrammatic framework. From a continuum perspective, the boundary theory is described by a set of scalar fields in similarity with the standard $K$-matrix Chern-Simons theory. The continuum theory recovers the gapped boundaries of the lattice model once we include sufficiently strong interactions that break charge conservation. The analysis of the perturbative relevance of the leading interactions reveals a regime in which the Chamon model can have a stable gapless fractonic phase at its boundary., Comment: 29 pages, 6 figures, extended discussions, references added, minor corrections

We describe scanning tunneling spectroscopic signatures of Majorana zero modes (MZMs) in Kitaev spin liquids. The tunnel conductance is determined by the dynamical spin correlations of the spin liquid, which we compute exactly, and by spin-anisotropic cotunneling form factors. Near a $\mathbb{Z}_2$ vortex, the tunnel conductance has a staircase voltage dependence, where conductance steps arise from MZMs and (at higher voltages) from additional vortex configurations. By scanning the probe tip position, one can detect the vortex locations. Our analysis suggests that topological magnon bound states near defects or magnetic impurities generate spectroscopic signatures that are qualitatively different from those of MZMs., Comment: 14 pages, 7 figures

Junctions of one-dimensional systems are of great interest to the development of synthetic materials that harbor topological phases. We study a junction of three gapless spin-1 chains described by the $\mathrm{SU(2)}_{2}$ Wess-Zumino-Wittten model and coupled by exchange and chiral three-spin interactions. We show that a chiral fixed point appears as a special point on the transition line separating two regimes described by open boundary conditions, corresponding to decoupled chains and the formation of a boundary spin singlet state. Along this transition line, the junction behaves as a tunable spin circulator as the spin conductance varies continuously with the coupling constant of a marginal boundary operator. Since the spectrum of the junction contains fractional excitations such as Majorana fermions, in this paper, we set the stage for network constructions of non-Abelian chiral spin liquids., Comment: 14 pages, 5 figures

Quantum spin systems can break time reversal symmetry by developing spontaneous magnetization or spin chirality. However, collinear magnets and chiral spin states are invariant under different symmetries, implying that the order parameter of one phase vanishes in the other. We show how to construct one-dimensional anisotropic spin models that exhibit a "Landau-forbidden" continuous phase transition between such states. As a concrete example, we focus on a zigzag chain with bond-dependent exchange and six-spin interactions. Using a combination of exact solutions, effective field theories, and numerical simulations, we show that the transition between the chiral and magnetic phases has an emergent U(1) symmetry. The excitations governing the transition from the chiral phase can be pictured as mobile defects in a $\mathbb Z_2$ flux configuration which bind fermionic modes. We briefly discuss extensions to two dimensions and analogies with deconfined quantum criticality. Our results suggest new prospects for unconventional phase transitions involving chiral spin states., Comment: 11 pages, 7 figures

Weyl semimetals harbor topological Fermi-arc surface states which determine the nontrivial charge current response to external fields. We here study the quasiparticle decay rate of Fermi arc states arising from their coupling to acoustic phonons, as well as the phonon-limited conductivity tensor for a clean Weyl semimetal slab. Using the phonon modes for an isotropic elastic continuum with a deformation potential coupling to electrons, we determine the temperature dependence of the quasiparticle decay rate, both near and far away from the arc termination points. By solving the coupled Boltzmann equations for the bulk and arc state distribution functions in the slab geometry, we show how the linear response conductivity depends on key parameters such as the temperature, the chemical potential, the geometric shape of the Fermi arcs, or the slab width. The chiral nature of Fermi arc states causes an enhancement of the longitudinal conductivity along the chiral direction at low temperatures, together with a 1/T^2 scaling regime at intermediate temperatures without counterpart for the conductivity along the perpendicular direction., Comment: 27 pages, 6 figures. Accepted version

Chiral three-spin interactions can suppress long-range magnetic order and stabilize quantum spin liquid states in frustrated lattices. We study a spin-1/2 model on the kagome lattice involving a staggered three-spin interaction $J_\chi$ in addition to Heisenberg exchange couplings $J_1$ on nearest-neighbor bonds and $J_d$ across the diagonals of the hexagons. We explore the phase diagram using a combination of a classical approach, parton mean-field theory, and variational Monte Carlo methods. We obtain a variety of noncoplanar magnetic orders, including a phase that interpolates between cuboc-1 and cuboc-2 states. In the regime of dominant $J_{\chi}$, we find a classically disordered region and argue that it may harbor a gapless chiral spin liquid with a spinon Fermi surface. Our results show that the competition between the staggered three-spin interaction and Heisenberg exchange interactions gives rise to unusual ground states of spin systems., Comment: Final version submitted to SciPost. New appendix about the nature of the classical ground state degeneracy

We show that line defects in a non-Abelian Kitaev spin liquid harbor gapless one-dimensional Majorana modes if the interaction across the defect falls below a critical value. Treating the weak interaction at the line defect within a mean-field approximation, we determine the critical interaction strength as a function of the external magnetic field. In the gapless regime, we use the low-energy effective field theory to calculate the spin-lattice relaxation rate for a nuclear spin near the defect and find a cubic temperature dependence that agrees with experiments in the Kitaev material $\alpha\text{-RuCl}_3$., Comment: 11 pages, 4 figures

Fracton phases of matter feature a variety of exciting phenomena stemming from the restricted mobility of their quasiparticles. Here we consider a model of interacting electrons in one dimension that describes hopping of spin-singlet pairs and obeys both charge and dipole conservation laws. The model contains Bethe ansatz integrable sectors which allow us to solve the ground state and calculate the exact spin and single-electron excitation gaps. We observe hallmarks of fractonic behavior, including localization of single-electron excitations and propensity to clustering. Our results demonstrate the important role of the dipole moment conservation law in a simple model of spin-1/2 fermions., Comment: 16 pages, 16 figures

We show that spin-spin correlations in a non-Abelian Kitaev spin liquid are associated with a characteristic inhomogeneous charge density distribution in the vicinity of $\mathbb{Z}_2$ vortices. This density profile and the corresponding local electric fields are observable, e.g., by means of surface probe techniques. Conversely, by applying bias voltages to several probe tips, one can stabilize Ising anyons ($\mathbb{Z}_2$ vortices harboring a Majorana zero mode) at designated positions, where we predict a clear Majorana signature in energy absorption spectroscopy., Comment: 14 pages, 5 figures

Weakly coupled Ising chains provide a condensed-matter realization of confinement. In these systems, kinks and antikinks bind into mesons due to an attractive interaction potential that increases linearly with the distance between the particles. While single mesons have been directly observed in experiments, the role of the multiparticle continuum and bound states of mesons in the excitation spectrum is far less clear. Using time-dependent density matrix renormalization group methods, we study the dynamical structure factors of one- and two-spin operators in a transverse-field two-leg Ising ladder in the ferromagnetic phase. The propagation of time-dependent correlations and the two-spin excitation spectrum reveal the existence of interchain bound states, which are absent in the one-spin dynamical structure factor. We also identify two-meson bound states that appear at higher energies, above the thresholds of several two-meson continua., Comment: 11 pages, 14 figures

We propose an exactly solvable model for $j_{\text{eff}}=\frac32$ local moments on the honeycomb lattice. Our construction is guided by a symmetry analysis and by the requirement of an exact solution in terms of a Majorana fermion representation for multipole operators. The main interaction in the model can be interpreted as a bond-dependent quadrupole-quadrupole interaction. When time reversal symmetry is explicitly broken, we obtain a gapped spin liquid with a single chiral Majorana edge mode. We also investigate another solvable model in which the time-reversal-invariant spin liquid is coupled to conduction electrons in a superconductor. In the presence of a Kondo-like coupling that involves the octupole moment of the localized spins, the itinerant electrons hybridize with the emergent Majorana fermions in the spin liquid. This leads to spontaneous time reversal symmetry breaking and generates odd-frequency pairing. Our results suggest that $j_{\text{eff}}=\frac32$ systems with strong quadrupole-quadrupole interactions may provide a route towards non-Abelian quantum spin liquids and unconventional superconductivity., Comment: 16 pages, 8 figures. We corrected the statement about the number of edge states in the chiral phase of the quadrupolar spin liquid. We also added the appendix B

The formation of bound states between mobile impurity particles and fermionic atoms has been demonstrated in spin-polarized Fermi gases with attractive interspecies interaction. We investigate bound states of mobile impurities immersed in a two-dimensional system with a symmetry-protected quadratic band touching. In addition to the standard s-wave interaction, we consider an anisotropic dipolar exchange interaction that locally breaks point group symmetries. Using a weak-coupling renormalization group approach and a ladder approximation for the impurity-fermion propagator, we establish that the number of bound states can be controlled by varying the anisotropy of the exchange interaction. Our results show that the degeneracy and momentum dependence of the binding energies reflect some distinctive properties of the quadratic band touching., Comment: 9 pages, 8 figures

We show that a honeycomb lattice of Heisenberg spin-$1/2$ chains with three-spin junction interactions allows for controlled analytical studies of chiral spin liquids (CSLs). Tuning these interactions to a chiral fixed point, we find a Kalmeyer-Laughlin CSL phase which here is connected to the critical point of a boundary conformal field theory. Our construction directly yields a quantized spin Hall conductance and localized spinons with semionic statistics as elementary excitations. We also outline the phase diagram away from the chiral point where spinons may condense. Generalizations of our approach can provide microscopic realizations for many other CSLs., Comment: 6 pages, 5 figures

We present an analytical low-energy theory of piezoelectric electron-phonon interactions in undoped Weyl semimetals, taking into account also Coulomb interactions. We show that piezoelectric interactions generate a long-range attractive potential between Weyl fermions. This potential comes with a characteristic angular anisotropy. From the one-loop renormalization group approach and a mean-field analysis, we predict that superconducting phases with either conventional s-wave singlet pairing or nodal-line triplet pairing could be realized for sufficiently strong piezoelectric coupling. For small couplings, we show that the quasi-particle decay rate exhibits a linear temperature dependence where the prefactor vanishes only in a logarithmic manner as the quasi-particle energy approaches the Weyl point. For practical estimates, we consider the Weyl semimetal TaAs., Comment: 18 pages, 7 figures. v2: typo corrected, comments about disorder and a separate section for quasi-particle lifetime added. Accepted version

The combination of non-Hermitian physics and strong correlations can give rise to new effects in open quantum many-body systems with balanced gain and loss. We propose a generalized Anderson impurity model that includes non-Hermitian hopping terms between an embedded quantum dot and two wires. These non-Hermitian hopping terms respect a parity-time ($\mathcal{PT}$) symmetry. In the regime of a singly occupied localized state, we map the problem to a $\mathcal{PT}$-symmetric Kondo model and study the effects of the interactions using a perturbative renormalization group approach. We find that the Kondo effect persists if the couplings are below a critical value that corresponds to an exceptional point of the non-Hermitian Kondo interaction. On the other hand, in the regime of spontaneously broken $\mathcal{PT}$ symmetry, the Kondo effect is suppressed and the low-energy properties are governed by a local-moment fixed point with vanishing conductance., Comment: 7 pages, 4 figures

Frustrated spin systems can show phases with spontaneous breaking of spin-rotational symmetry without the formation of local magnetic order. We study the dynamic response of the spin-nematic phase of one-dimensional spin-1/2 systems, characterized by slow large-distance decay of quadrupolar correlations, by numerically computing one-spin and two-spin dynamical structure factors at zero temperature using time-dependent density matrix renormalization group methods. We interpret the results in terms of an effective theory of gapped magnon excitations interacting with a quasi-condensate of bound magnon pairs. This employs an extension of the well-known Tomonaga-Luttinger liquid theory which includes the magnon states as a mobile impurity. A good qualitative understanding of the characteristic thresholds and their intensity in the structure factors is obtained this way. Our results are useful in the interpretation of inelastic neutron scattering and resonant inelastic x-ray scattering experiments., Comment: 15 pages, 10 figures

We study the effective spin-orbital model that describes the magnetism of 4$d^1$ or 5$d^1$ Mott insulators in ideal tricoordinated lattices. In the limit of vanishing Hund's coupling, the model has an emergent SU(4) symmetry which is made explicit by means of a Klein transformation on pseudospin degrees of freedom. Taking the hyperhoneycomb lattice as an example, we employ parton constructions with fermionic representations of the pseudospin operators to investigate possible quantum spin-orbital liquid states. We then use variational Monte Carlo (VMC) methods to compute the energies of the projected wave functions. Our numerical results show that the lowest-energy quantum liquid corresponds to a zero-flux state with a Fermi surface of four-color fermionic partons. In spite of the Fermi surface, we demonstrate that this state is stable against tetramerization. A combination of linear flavor wave theory and VMC applied to the complete microscopic model also shows that this liquid state is stable against the formation of collinear long-range order., Comment: 15 pages,11 figures. The updated version includes two corrections: the inclusion of neglected terms on the complete model (Eqs. (17)-(20)) and the assignment of the sublattices for the Klein transformation (this was presupposed in the first version, but incorrectly assigned). The stability of the QSOL was studied using a combination of LFWT and VMC

Using a perturbative renormalization group approach, we show that the extended ($J_1$-$J_2$-$J_d$) Heisenberg model on the kagome lattice with a staggered chiral interaction ($J_\chi$) can exhibit a gapless chiral quantum spin liquid phase. Within a coupled-chains construction, this phase can be understood as a chiral sliding Luttinger liquid with algebraic decay of spin correlations along the chain directions. We calculate the low-energy properties of this gapless chiral spin liquid using the effective field theory and show that they are compatible with the predictions from parton mean-field theories with symmetry-protected line Fermi surfaces. These results may be relevant to the state observed in the kapellasite material., Comment: 28 pages, 5 figures

We describe a coupled-chain construction for chiral spin liquids in two-dimensional spin systems. Starting from a one-dimensional zigzag spin chain and imposing SU(2) symmetry in the framework of non-Abelian bosonization, we first show that our approach faithfully describes the low-energy physics of an exactly solvable model with a three-spin interaction. Generalizing the construction to the two-dimensional case, we obtain a theory that incorporates the universal properties of the chiral spin liquid predicted by Kalmeyer and Laughlin: charge-neutral edge states, gapped spin-1/2 bulk excitations, and ground state degeneracy on the torus signalling the topological order of this quantum state. In addition, we show that the chiral spin liquid phase is more easily stabilized in frustrated lattices containing corner-sharing triangles, such as the extended kagome lattice, than in the triangular lattice. Our field theoretical approach invites generalizations to more exotic chiral spin liquids and may be used to assess the existence of the chiral spin liquid as the ground state of specific lattice systems., Comment: 12 pages, 8 figures

Some well-established examples of itinerant-electron ferromagnetism in one dimension occur in a Mott-insulating phase. We examine the consequences of doping a ferromagnetic insulator and cou- pling magnons to gapless charge fluctuations. Using a bosonization scheme for strongly interacting electrons, we derive an effective field theory for the magnon-holon interaction. When the magnon momentum matches the Fermi momentum of the holons, the backscattering of the magnon at low energies gives rise to a Kondo effect of a pseudospin defined from the chirality degree of freedom (right- or left-moving particles). The crossover between weak-coupling and strong-coupling fixed points of the effective mobile-impurity model is then investigated using a numerical renormalization group approach., Comment: 21 pages, 12 figures

An overview is given of the limitations of Luttinger liquid theory in describing the real time equilibrium dynamics of critical one-dimensional systems with nonlinear dispersion relation. After exposing the singularities of perturbation theory in band curvature effects that break the Lorentz invariance of the Tomonaga-Luttinger model, the origin of high frequency oscillations in the long time behaviour of correlation functions is discussed. The notion that correlations decay exponentially at finite temperature is challenged by the effects of diffusion in the density-density correlation due to umklapp scattering in lattice models., Comment: 17 pages, 3 figures. Short review to appear in the Luttinger Liquids special issue of Int. J. Mod. Phys. B; reference added

We discuss an approximation for the dynamic charge response of nonlinear spin-1/2 Luttinger liquids in the limit of small momentum. Besides accounting for the broadening of the charge peak due to two-holon excitations, the nonlinearity of the dispersion gives rise to a two-spinon peak, which at zero temperature has an asymmetric line shape. At finite temperature the spin peak is broadened by diffusion. As an application, we discuss the density and temperature dependence of the Coulomb drag resistivity due to long-wavelength scattering between quantum wires., Comment: 16 pages, 5 figures. This is an extended version of "Coulomb drag from spin-charge coupling at zero magnetic field"

We study the spectral function of interacting one-dimensional fermions for an integrable lattice model away from half-filling. The divergent power-law singularity of the spectral function near the single-particle or single-hole energy is described by an effective x-ray edge type model. At low densities and for momentum near the zone boundary, we find a second divergent singularity at higher energies which is associated with a two-particle bound state. We use the Bethe ansatz solution of the model to calculate the exact singularity exponents for any momentum and for arbitrary values of chemical potential and interaction strength in the critical regime. We relate the singularities of the spectral function to the long-time decay of the fermion Green's function and compare our predictions with numerical results from the time-dependent density matrix renormalization group (tDMRG). Our results show that the tDMRG method is able to provide accurate time decay exponents in the cases of power-law decay of the Green's function. Some implications for the line shape of the dynamical structure factor away from half-filling are also discussed. In addition, the spectral weight of the Luttinger liquid result for the dynamical structure factor of the Heisenberg model at zero field is compared with the exact two-spinon contribution., Comment: 30 pages, 18 figures

We propose that the finite size of the Kondo screening cloud, xi_K, can be probed by measuring the charge quantization in a one-dimensional system coupled to a small quantum dot. When the chemical potential, mu in the system is varied at zero temperature, one should observe charge steps whose locations are at values of mu that are controlled by the Kondo effect when the system size L is comparable to xi_K. We show that, if the standard Kondo model is used, the ratio between the widths of the Coulomb blockade valleys with odd or even number of electrons is a universal scaling function of xi_K/L. If we take into account electron-electron interactions in a single-channel wire, this ratio also depends on the parameters of the effective Luttinger model; in addition, the scaling is weakly violated by a marginal bulk interaction. For the geometry of a quantum dot embedded in a ring, we show that the dependence of the charge steps on a magnetic flux through the ring is controlled by the size of the Kondo screening cloud., Comment: This is an extended version of cond-mat/0612635 with an analysis of bulk Luttinger liquid interactions added as well as a discussion of experimental possibilities

Exact formulas for the singularities of the dynamical structure factor, S^{zz}(q,omega), of the S=1/2 xxz spin chain at all q and any anisotropy and magnetic field in the critical regime are derived, expressing the exponents in terms of the phase shifts which are known exactly from the Bethe ansatz solution. We also study the long time asymptotics of the self-correlation function <0|S_j^z(t)S_j^z(0)|0>. Utilizing these results to supplement very accurate time-dependent Density Matrix Renormalization Group (DMRG) for short to moderate times, we calculate S^{zz}(q,omega) to very high precision., Comment: 4 pages, 1 figure, 1 table, published version

We propose that the finite size of the Kondo screening cloud, xi_K, can be probed by measuring the charge quantization in a one-dimensional system coupled to a small quantum dot. When the chemical potential in the system is varied at zero temperature, one should observe charge steps that are controlled by the Kondo effect when the system size L is comparable to xi_K. We show that, if the standard Kondo model is used, the ratio between the widths of the Coulomb blockade valleys with odd or even number of electrons is a universal scaling function of xi_K/L., Comment: An extended version of this paper is now available at: 0801.4166. An analysis of bulk Luttinger liquid interactions has been added as well as a discussion of experimental possibilities