Ballistic-to-Localized Dynamics as Signature of Quantum Phase Transition in Josephson Junction
Abstract
Using state-of-the-art numerical techniques, we investigate how quantum phase fluctuations and quasiparticle tunneling shape the behavior of a small-capacitance Josephson junction across Ohmic, sub-Ohmic, and super-Ohmic dissipation regimes. We show that increasing the Ohmic dissipation strength drives a Berezinskii-Kosterlitz-Thouless quantum phase transition at thermodynamic equilibrium. Deviations from Ohmic behavior profoundly alter this scenario: the super-Ohmic regime exhibits no phase transition, whereas the sub-Ohmic regime displays a continuous second-order transition, consistent with the universality classes of the spin-boson model. Within the Ohmic regime, real-frequency linear-response calculations reveal that the phase particle does not undergo the commonly assumed diffusive-to-localized crossover. Instead, finite resistance progressively suppresses the singular zero-frequency response, producing a ballistic-to-localized change in the dynamics. At finite frequencies, coupling to the environment generates a long-lived excitation in the charge response, which evolves into a resonance as the subgap and shunt resistances are reduced.
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BibTeX
@misc{capone2026ballistictolocalized,
title = {{Ballistic-to-Localized Dynamics as Signature of Quantum Phase Transition in Josephson Junction}},
author = {F. G. Capone and A. de Candia and G. Di Bello and V. Cataudella and R. Fazio and N. Nagaosa and C. A. Perroni and G. De Filippis},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2608.29830},
eprint = {2608.29830},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.29830},
}
RIS
TY - UNPB
TI - Ballistic-to-Localized Dynamics as Signature of Quantum Phase Transition in Josephson Junction
AU - F. G. Capone
AU - A. de Candia
AU - G. Di Bello
AU - V. Cataudella
AU - R. Fazio
AU - N. Nagaosa
AU - C. A. Perroni
AU - G. De Filippis
PY - 2026
DA - 2026/08/30
PB - arXiv
DO - 10.48550/arxiv.2608.29830
UR - https://arxiv.org/abs/2608.29830
AB - Using state-of-the-art numerical techniques, we investigate how quantum phase fluctuations and quasiparticle tunneling shape the behavior of a small-capacitance Josephson junction across Ohmic, sub-Ohmic, and super-Ohmic dissipation regimes. We show that increasing the Ohmic dissipation strength drives a Berezinskii-Kosterlitz-Thouless quantum phase transition at thermodynamic equilibrium. Deviations from Ohmic behavior profoundly alter this scenario: the super-Ohmic regime exhibits no phase transition, whereas the sub-Ohmic regime displays a continuous second-order transition, consistent with the universality classes of the spin-boson model. Within the Ohmic regime, real-frequency linear-response calculations reveal that the phase particle does not undergo the commonly assumed diffusive-to-localized crossover. Instead, finite resistance progressively suppresses the singular zero-frequency response, producing a ballistic-to-localized change in the dynamics. At finite frequencies, coupling to the environment generates a long-lived excitation in the charge response, which evolves into a resonance as the subgap and shunt resistances are reduced.
ER -