Cǎtǎlin Paşcu Moca

6604083229

Publications - 4

Dissipative dynamics in the free massive boson limit of the sine-Gordon model

Ádám Bácsi Balázs Dóra Balázs Dóra Cǎtǎlin Paşcu Moca Gergely Zarand

Publication Name: Scipost Physics Core

Publication Date: 2022-01-01

Volume: 5

Issue: 1

Page Range: Unknown

Description:

We study the dissipative dynamics of one-dimensional fermions, described in terms of the sine-Gordon model in its free massive boson or semi-classical limit, while keeping track of forward scattering processes. The system is prepared in the gapped ground state, and then coupled to environment through local currents within the Lindblad formalism. The heating dynamics of the system is followed using bosonization. The single particle density matrix exhibits correlations between the left and right moving particles. While the density matrix of right movers and left movers is translationally invariant, the left-right sector is not, corresponding to a translational symmetry breaking charge density wave state. Asymptotically, the single particle density matrix decays exponentially with exponent proportional to -γt|x|∆2 where γ and ∆ are the dissipative coupling and the gap, respectively. The charge density wave order parameter decays exponentially in time with an interaction independent decay rate. The second Rényi entropy grows linearly with time and is essentially insensitive to the presence of the gap.

Open Access: Yes

DOI: 10.21468/SciPostPhysCore.5.1.004

Vaporization Dynamics of a Dissipative Quantum Liquid

Ádám Bácsi Balázs Dóra Balázs Dóra Cǎtǎlin Paşcu Moca Gergely Zarand

Publication Name: Physical Review Letters

Publication Date: 2020-12-30

Volume: 125

Issue: 26

Page Range: Unknown

Description:

We investigate the stability of a Luttinger liquid, upon suddenly coupling it to a dissipative environment. Within the Lindblad equation, the environment couples to local currents and heats the quantum liquid up to infinite temperatures. The single particle density matrix reveals the fractionalization of fermionic excitations in the spatial correlations by retaining the initial noninteger power law exponents, accompanied by an exponential decay in time with an interaction dependent rate. The spectrum of the time evolved density matrix is gapped, which collapses gradually as -ln(t). The von Neumann entropy crosses over from the early time -tln(t) behavior to ln(t) growth for late times. The early time dynamics is captured numerically by performing simulations on spinless interacting fermions, using several numerically exact methods. Our results could be tested experimentally in bosonic Luttinger liquids.

Open Access: Yes

DOI: 10.1103/PhysRevLett.125.266803

Dissipation-Induced Luttinger Liquid Correlations in a One-Dimensional Fermi Gas

Ádám Bácsi Balázs Dóra Balázs Dóra Cǎtǎlin Paşcu Moca

Publication Name: Physical Review Letters

Publication Date: 2020-04-03

Volume: 124

Issue: 13

Page Range: Unknown

Description:

We study a one-dimensional Fermi gas in the presence of dissipative coupling to environment through the Lindblad equation. The dissipation involves energy exchange with the environment and favours the relaxation of electrons to excitations. After switching on the dissipation, the system approaches a steady state, which is described by a generalized Gibbs ensemble. The fermionic single particle density matrix resembles deceivingly to that in a hermitian interaction quench. It decays inversely with the distance for short times due to the fermionic correlations in the initial state, which changes into a noninteger power law decay for late times, representing dissipation-induced Luttinger liquid behavior. However, the crossover between the two regions occurs due to dissipation-induced damping, and is unrelated to the propagation of excitations. The velocity of information spreading is set by the dissipative coupling, and differs significantly from the original sound velocity. The thermodynamic entropy grows as -t ln t initially, and saturates to an extensive value. Our results can be tested experimentally in one-dimensional Dirac systems.

Open Access: Yes

DOI: 10.1103/PhysRevLett.124.136401

Infinite-temperature spin dynamics in the asymmetric Hatsugai-Kohmoto model

Ádám Bácsi Doru Sticlet Balázs Dóra Cǎtǎlin Paşcu Moca

Publication Name: Physical Review B

Publication Date: 2025-10-14

Volume: 112

Issue: 15

Page Range: Unknown

Description:

We focus on the infinite-temperature dynamical spin structure factor of the asymmetric Hatsugai-Kohmoto model, a relative of the asymmetric Hubbard model. It is characterized by distinct single-particle energies for the two spin species, which interact with each other through a contact interaction in momentum space. We evaluate its spin structure factor exactly and follow the evolution of its excitation spectrum for all fillings and interactions, identifying signatures of the Mott transition and fingerprints of the asymmetric hoppings. The longitudinal spin structure factor exhibits soundlike and interaction-induced gapped excitations, whose number gets doubled in the presence of hopping asymmetry. The transverse response displays the competition of interaction- and asymmetry-induced gaps and results in a quadratic excitation branch at their transition. The complete asymmetric case features a momentum-independent dynamical structure factor, characteristic of transitions involving a flat band.

Open Access: Yes

DOI: 10.1103/7bc3-3jz9