Decay of correlations in the dissipative two-state system
Institut für Theoretische Physik, Universität
Stuttgart - D-70550 Stuttgart, Germany
2 Istituto di Fisica, Università di Catania and INFM, Viale A. Doria 6, 95129 Catania, Italy
Accepted: 22 May 1998
We study the equilibrium correlation function of the polaron-dressed tunnelling operator in the dissipative two-state system and compare the asymptoptic dynamics with that of the position correlations. For an Ohmic spectral density with damping strength , the correlation functions are obtained in analytic form for all times at any T and any bias. For K<1, the asymptotic dynamics is found by using a diagrammatic approach within a Coulomb gas representation. At T=0, the tunnelling or coherence correlations drop as , whereas the position correlations show universal decay . The former decay law is a signature of unscreened attractive charge-charge interactions, while the latter is due to unscreened dipole-dipole interactions.
PACS: 05.30.-d – Quantum statistical mechanics / 05.40.+j – Fluctuation phenomena, random processes, and Brownian motion / 73.40.Gk – Tunneling
© EDP Sciences, 1998