Recursive Method for the Density of States in One Dimension

We derive a powerful yet simple method for analyzing the local density of states in gapless one dimensional fermionic systems, including extensions such as momentum dependent interaction parameters and hard-wall boundaries. We study the crossover of the local DOS from individual density waves to the well-known asymptotic powerlaws and identify characteristic signs of spin charge separation in possible STM experiments. For semi-infinite systems a closed analytic expression is found in terms of hypergeometric functions.Comment: 5 pages and 3 figures. The latest version can be found at http://www.physik.uni-kl.de/eggert/papers/index.htm

Magnetic order and moment distribution in doped spin-chain systems

We consider the effect of doping on the magnetic order in quasi one-dimensional (1D) antiferromagnets. First the detailed magnetic response of finite spin-1/2 chains in the presence of a staggered field is determined, which by itself shows an interesting crossover as function of length and field strength. We can then understand the ordering by including an effective coupling between the chains, which results in a Neel ordered phase at low temperatures, but with a broad distribution of magnetic moments that has to be determined self-consistently.Comment: 2 pages, 1 figure. Latest pdf-file is available at http://www.physik.uni-kl.de/eggert/papers/magorder.pd

A Luttinger Liquid in Box

We study a Luttinger Liquid in a finite one-dimensional wire with box-like boundary conditions by considering the local distribution of the single particle spectral weight. This corresponds to the experimental probability of extracting a single electron at a given place and energy, which can be interpreted as the square of an electron wave-function. For the non-interacting case, this is given by a standing wave at the Fermi wave-vector. In the presence of interactions, however, the wave-functions obtain additional structure with a sharp depletion near the edges and modulations throughout the wire. In the spinful case, these modulations correspond to the separate spin- and charge-like excitations in the system.Comment: 5 pages in revtex4 format including 3 epsf-embedded figures. The latest version in PDF format is available from http://fy.chalmers.se/~eggert/papers/LLbox.pd

Knight shifts around vacancies in the 2D Heisenberg model

The local response to a uniform field around vacancies in the two-dimensional (2D) spin-1/2 Heisenberg antiferromagnet is determined by numerical quantum Monte Carlo simulations as a function of temperature. It is possible to separate the Knight shifts into uniform and staggered contributions on the lattice which are analyzed and understood in detail. The contributions show interesting long and short range behavior that may be of relevance in NMR and susceptibility measurements. For more than one impurity remarkable non-linear enhancement and cancellation effects take place. We predict that the Curie impurity susceptibility will be observable for a random impurity concentration even in the thermodynamic limit.Comment: 5 pages, 4 figures, submitted to Phys. Rev. Lett. The latest pdf version can be found at http://www.physik.uni-kl.de/eggert/papers/knight.pd

A two-channel Kondo impurity in the spin-1/2 chain: Consequences for Knight shift experiments

A magnetic impurity in the spin-1/2 chain is a simple realization of the two-channel Kondo problem since the field theoretical descriptions in the spin-sector are identical. The correlation functions near the impurity can be calculated. Using a modified version of the numerical transfer matrix DMRG, we are able to accurately determine local properties close to the impurity in the thermodynamic limit. The local susceptibilities (Knight-shifts) show an interesting behavior in a large range around the impurities. We are able to make quantitative experimental predictions which would allow to observe two-channel Kondo physics for the first time directly by doping of spin-1/2 chain compounds.Comment: 2 pages in revtex format including 2 embedded figures (using epsf