Relaxation to Negative Temperatures in Double Domain Systems

TL;DR

This paper studies how two coupled spin domains relax when interacting with a common reservoir, revealing conditions under which the system reaches negative-temperature states, especially with antiparallel and unbalanced initial configurations.

Contribution

It demonstrates the relaxation dynamics of double domain spin systems and identifies conditions leading to negative-temperature states, a novel insight in quantum thermodynamics.

Findings

Negative-temperature states occur in unbalanced initial configurations.

Antiparallel spin domain configurations facilitate unique relaxation pathways.

System relaxation depends on the initial spin distribution and domain sizes.

Abstract

We investigate the relaxation of two collective spins in double domain system, which are individually coupled to a single bosonic reservoir, by varying the total number of spins in each domain and their initial spin configurations. A particularly interesting situation occurs when the spin domains are set in an antiparallel configuration. Further for an unbalanced configuration where the number of spins are in the excited state initially is much greater than that in the ground state, the spin ensemble prepared in the ground state relaxes towards a negative-temperature state.