We present release 1.3 of the ALPS (Algorithms and Libraries for Physics Simulations) project, an international open source software project to develop libraries and application programs for the simulation of strongly correlated quantum lattice models such as quantum magnets, lattice bosons, and strongly correlated fermion systems. Development is centered on common XML and binary data formats, on libraries to simplify and speed up code development, and on full-featured simulation programs. The programs enable non-experts to start carrying out numerical simulations by providing basic implementations of the important algorithms for quantum lattice models: classical and quantum Monte Carlo (QMC) using non-local updates, extended ensemble simulations, exact and full diagonalization (ED), as well as the density matrix renormalization group (DMRG). Changes in the new release include a DMRG program for interacting models, support for translation symmetries in the diagonalization programs, the ability to define custom measurement operators, and support for inhomogeneous systems, such as lattice models with traps. The software is available from our web server at http://alps.comp-phys.org/.

High resolution neutron powder diffraction and single crystal measurements on the ferromagnetic shape memory compound Ni 2 MnGa have been carried out. They enabled the sequence of transformations which take place when the unstressed, stoichiometric compound is cooled from 400 to 20 K to be established. For the first time the crystallographic structure of each of the phases which occur has been determined. At 400 K the compound has the cubic L2 1 structure, and orders ferromagnetically at T C ≈ 365 K. On cooling below ∼260 K a super-structure, characterized by tripling of the repeat in one of the 110 cubic directions, forms. This phase, known as the pre-martensitic phase, persists down to the structural phase transition at T M ≈ 200 K and can be described by an orthorhombic unit cell with lattice parameters a ortho = 1 √ 2 a cubic , b ortho = 3 √ 2 a cubic , c ortho = a cubic and space group Pnnm. Below T M the compound has a related orthorhombic super-cell with b ortho ≈ 7 √ 2 a cubic , which can be described within the same space group. The new modulation appears abruptly at T M and remains stable down to at least 20 K.

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The electronic states near a surface or a domain wall in the p-wave superconductor are studied for the order parameter of the form p x ±ip y -wave, which is a unitary odd-parity state with broken time-reversal symmetry. This state has been recently suggested as the superconducting state of Sr 2 RuO 4 . The spatial variation of the order parameter and vector potential is determined selfconsistently within the quasi-classical approximation. The local density of states at the surface is constant and does not show any peak-like or gap-like structure within the superconducting energy gap, in contrast to the case of the d-wave superconductors. The influence of an external magnetic field is mainly observable in the energy range above the bulk gap. On the other hand, there is a small energy gap in the local density of states at the domain wall between domains of the two degenerate p x +ip y -wave and p x −ip y -wave states.KEYWORDS: Sr2RuO4, p-wave superconductor, unitary state, time-reversal breaking state, boundary effect, surface, domain wall, quasi-classical theory, Ginzburg-Landau free energy §1. Introduction Sr 2 RuO 4 is the first superconductor with layered perovskite structure, which does not contain copper. 1) Although the structure is identical to that of some of the high-temperature superconductors, the transition temperature is rather low, T C =1.5K. There is a clear difference in the electronic structure, since Sr 2 RuO 4 is a good metal and even a Fermi liquid in its stoichiometric composition.Band structure calculations in good agreement with the de Haas-van Alphen measurements show that this compound has three Fermi surfaces originating from the three 4d-t 2g -orbitals of Ru 4+ . 2,3,4) There is growing experimental evidence that the superconducting state is unconventional (non-swave). Examples are the absence of a Hebel-Slichter peak in 1/T 1 T of NQR-measurements 5) and the sensitivity of T C on non-magnetic impurities. 6) It was suggested that the superconducting state has odd-parity (spin triplet) pairing. 7,8,10,9,11) There is a certain similarity with 3 He considering the correlation effects (superfluid 3 He has pwave pairing). 7) Furthermore, there is a series of related compounds such as SrRuO 3 which are 1 ferromagnetic suggesting that ferromagnetic spin fluctuations are probably enhanced in Sr 2 RuO 4 and mediate odd-parity, spin triplet pairing. 12,7,13) The recent discovery of intrinsic magnetism in the superconducting phase by µSR experiments indicates a pairing state with broken time reversal symmetry. 14) Symmetry considerations lead to the conclusion that this would only be possible for an odd-parity state. 15) A very strong support for odd-parity pairing comes also from the Knight shift data in the 17 O-NMR measurements which demonstrate the absence of any reduction of the spin susceptibility in the superconducting state. 16) The superconducting state compatible with all of these experiments is given by d(k)=ẑ(k x ±ik y ). 15) The presence of three electron bands forming the Fermi liqui...