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Medientyp:
E-Artikel
Titel:
Partial thermalisation of a two-state system coupled to a finite quantum bath
Beteiligte:
Crowley, Philip;
Chandran, Anushya
Erschienen:
Stichting SciPost, 2022
Erschienen in:
SciPost Physics, 12 (2022) 3
Sprache:
Nicht zu entscheiden
DOI:
10.21468/scipostphys.12.3.103
ISSN:
2542-4653
Entstehung:
Anmerkungen:
Beschreibung:
The eigenstate thermalisation hypothesis (ETH) is a statisticalcharacterisation of eigen-energies, eigenstates and matrix elements oflocal operators in thermalising quantum systems. We develop an ETH-likeansatz of a partially thermalising system composed of aspin-\tfrac{1}{2}12coupled to a finite quantum bath. The spin-bath coupling is sufficientlyweak that ETH does not apply, but sufficiently strong that perturbationtheory fails. We calculate (i) the distribution of fidelitysusceptibilities, which takes a broadly distributed form, (ii) thedistribution of spin eigenstate entropies, which takes a bi-modal form,(iii) infinite time memory of spin observables, (iv) the distribution ofmatrix elements of local operators on the bath, which is non-Gaussian,and (v) the intermediate entropic enhancement of the bath, whichinterpolates smoothly between S = 0S=0and the ETH value of S = \log 2S=log2.The enhancement is a consequence of rare many-body resonances, and isasymptotically larger than the typical eigenstate entanglement entropy.We verify these results numerically and discuss their connections to themany-body localisation transition.