gharib85/xxzspinchain

Quantum spin chain Hamiltonian in presence of magnetic field

XXZspinchain

Quantum spin chain Hamiltonian in presence of magnetic field

The various functions that are included are used to calculate the eigenvalues of the Hamiltonian op a quantum spin chain (QSC). The calculated eigenvalues of the Hamiltonian operator represent energy values. We allow for a magnetic field to work on the QSC, and we are interested in the lowest eigenvalues of the system. Some additional function allows us to use a small orthogonal basis constructed out of the known eigenvectors at two specified points. From this basis it is possible to approximate the real eigenvalues, but a lot faster.

Running the code for long chains, say more than 17 atoms, WILL take a long time, especially if one wants to know the eigenvalues at a lot of steps of the magneticfield. e.g. Calculating 10 eigenvalues at 250 steps of the magnetic field strength for a 19 atoms chain can take several hours!

A DMRG method module has been included, the main part of this code has been copied from https://github.com/simple-dmrg/simple-dmrg/. Here we added the feature to activate a magnetic field. Al the credits for the rest of the program go to the original writers James R. Garrison and Ryan V. Mishmash.

Also a multiprocessing module and two functions to build Hamiltonian matrices for (next-)next-nearest neighbour interactions are included.