Dynamics of the two-spin spin-boson model with a common bath

Area of Science:

• Quantum mechanics
• Condensed matter physics

Background:

• The spin-boson model (SBM) is crucial for understanding quantum systems interacting with their environment.
• Accurate simulation of SBM dynamics is essential for predicting system behavior.

Purpose of the Study:

• To investigate the dynamics of the two-spin spin-boson model using an advanced simulation technique.
• To assess the accuracy and validity of the multi-D1 Ansatz across different coupling regimes and bath types.

Main Methods:

• Employed the multi-Davydov D1 Ansatz (multi-D1 Ansatz) for dynamics simulations.
• Systematically examined the Ansatz's validity using a deviation vector.
• Studied time evolution of population difference and entanglement.
• Compared results with time-dependent numerical renormalization group (TD-NRG), Bloch-Redfield theory, and variational master equation methods.

Main Results:

• The multi-D1 Ansatz shows improved accuracy over the single D1 Ansatz, particularly in weak to moderate coupling.
• In the strong coupling Ohmic bath regime, results align with TD-NRG.
• In the strong coupling sub-Ohmic bath regime, the multi-D1 Ansatz is more accurate than TD-NRG.
• In the weak coupling regime, the multi-D1 Ansatz agrees with master-equation methods but differs from TD-NRG in sub-Ohmic baths.

Conclusions:

• The multi-D1 Ansatz provides a reliable and accurate method for simulating two-spin spin-boson model dynamics.
• The study highlights potential limitations of TD-NRG in sub-Ohmic bath scenarios at long times.
• This work offers a more accurate computational tool for quantum dynamics research.