Natan Andrei

Heisenberg chain with impurities (an integrable model)

Abstract We present an integrable model describing the interaction of spin- S impurities with an isotropic Heisenberg chain. The model is diagonalized and its thermodynamics formulated.

Kondo-stabilised spin liquids and heavy fermion superconductivity

The authors consider an SU(2) path integral formulation of a Kondo lattice model for heavy fermions that treats the RKKY interaction explicitly. At low temperatures they find the heavy Fermi liquid becomes unstable to the formation of a spin liquid amongst the f spins. Kondo coupling to the spin liquid stabilises it against antiferromagnetism, causing the resonating valence bonds of the spin liquid to occasionally escape into the conduction sea. This process induces off-diagonal resonant scattering in the conduction sea, thereby generating anisotropic superconductivity in the heavy fermion system.

Nonequilibrium Transport in Quantum Impurity Models: The Bethe Ansatz for Open Systems

We develop an exact nonperturbative framework to compute steady-state properties of quantum impurities subject to a finite bias. We show that the steady-state physics of these systems is captured by nonequilibrium scattering eigenstates which satisfy an appropriate Lippman-Schwinger equation. Introducing a generalization of the equilibrium Bethe ansatz--the nonequilibrium Bethe ansatz--we explicitly construct the scattering eigenstates for the interacting resonance level model and derive exact, nonperturbative results for the steady-state properties of the system.

Dynamical symmetry breaking and fractionization in a new integrable model

We propose and investigate a new O(n)-invariant exactly integrable model. The model is found to undergo dynamical symmetry breaking and hence contain quantum-kink excitations. Surprisingly, the quantum numbers carried by the kink excitations are partially fractionized. As a consequence the spectrum is found to contain only even but no odd-particle sectors.

Calculation of the magnetoresistance in the Kondo model

Abstract Using the exact diagonalization of the model we calculate the resistivity for arbitrary magnetic fields at zero temperature.

Failure of the local generalized Gibbs ensemble for integrable models with bound states

In this work we study the applicability of the local GGE to integrable one dimensional systems with bound states. We find that the GGE, when defined using only local conserved quantities, fails to describe the long time dynamics for most initial states including eigenstates. We present our calculations studying the attractive Lieb-Liniger gas and the XXZ magnet, though similar results may be obtained for other models.

Integrable Models in Condensed Matter Physics

This is an expanded version of the lectures given at the Trieste Summer School 1992 on Low-dimensional Quantum Field Theories for Condensed Matter Physicists.

Thermal conductivity of spin-12chains

We study the low-temperature transport properties of clean one-dimensional spin-

Electrically controlled pumping of spin currents in topological insulators

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SOLUTION OF THE MULTICHANNEL COQBLIN-SCHRIEFFER IMPURITY MODEL AND APPLICATION TO MULTILEVEL SYSTEMS

chains coupled to phonons. Due to the presence of approximate conservation laws, the heat current decays very slowly giving rise to an exponentially large heat conductivity,