Abstract
We investigate the dynamics brought on by an impulse perturbation in two infinite-range quantum Ising models coupled to each other and to a dissipative bath. We show that, if dissipation is faster the higher the excitation energy, the pulse perturbation cools down the low-energy sector of the system, at the expense of the high-energy one, eventually stabilising a transient symmetry-broken state at temperatures higher than the equilibrium critical one. Such non-thermal quasi-steady state may survive for quite a long time after the pulse, if the latter is properly tailored.
Highlights
Until now the most remarkable failure of the naïve correspondence between light firing and thermal heating is the evidence of superconducting-like behaviour at nominal temperatures far higher than the critical one in the molecular conductors K3C60 and κ-(BEDTTTF)2Cu[N(CN)2]Br irradiated by laser pulses [12–14]
In an attempt to explain the photoinduced superconductivity in K3C60 [12], a different laser cooling mechanism was proposed in Ref. [20], which is essentially based on the existence of a high energy localised mode that, when the laser is on, is able to fast absorb entropy from the thermal bath of low-energy particle-hole excitations, while, after the end of the laser pulse, it release back that absorbed entropy very slowly
In this paper we have investigated the transient cooling mechanism brought on by a pulse perturbation in the two coupled infinite-range quantum Ising models of Ref. [21], but in presence of dissipation
Summary
I, j=1 i=1 and σαn,i, α = x, y, z, are Pauli matrices on site i = 1, . J, h1, h2 and λ are assumed positive. Hereafter we take J = 1 as energy unit. N,i m, j n,i n, j which implies that the mean-field approximation becomes exact in the thermodynamic limit N → ∞, or, equivalently, that the full density matrix ρfactorises in that limit into the product of single-site density matrices:. N →∞ i=1 where ρi are positive definite 4 × 4 matrices with unit trace. The property (4) allows exactly solving with relative ease the model Hamiltonian (1)
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