Finite-temperature dynamical correlations using the microcanonical ensemble and the Lanczos algorithm

Martin Long, P Prelovsek, S El Shawish

Research output: Contribution to journalArticle

49 Citations (Scopus)

Abstract

We show how to generalize the zero-temperature Lanczos method for calculating dynamical correlation functions to finite temperatures. The key is the microcanonical ensemble which allows us to replace the involved canonical ensemble with a single appropriately chosen state; in the thermodynamic limit it provides the same physics as the canonical ensemble but with the evaluation of a single expectation value. We can employ the same system sizes as for zero temperature but, whereas the statistical fluctuations present in small systems are prohibitive, the spectra of the largest system sizes are surprisingly smooth. We investigate, as a test case, the spin conductivity of the spin-1/2 anisotropic Heisenberg model and in particular we present a comparison of spectra obtained by the canonical and microcanonical ensemble methods.
Original languageEnglish
Pages (from-to)235106
Number of pages1
JournalPhysical Review B
Volume68
Issue number23
Early online date1 Dec 2003
DOIs
Publication statusPublished - 1 Dec 2003

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