RQC Seminar

62nd RQC Seminar

• Speaker

  Mr. Daniele Lamberto
  ( Università degli Studi di Messina, Dipartimento di Scienze Matematiche e Informatiche, Scienze Fisiche e Scienze della Terra (MIFT) )

• Date

  16:00-17:00, July 20th, 2023 (Thursday)

• Venue

  Hybrid(ZOOM・ Wako Main Research 3F 345-347 Seminar Room)

• Title

  On the Impossibility of Superradiant Phase Transitions in Many-Dipole Cavity-QED Systems

• Inquiries

  rqc_info[at]ml.riken.jp

Abstract
The possibility of a phase transition between a normal and a photon condensate state (also known as superradiant phase transitions, SPT) in light-matter systems under (electric) dipolar interactions is the subject of much debate, due to numerous apparently conflicting no-go and counter no-go theorems (see, e.g., [1, 2, 3, 4]). It is worth pointing out that the debate is limited to the case of (electric) dipolar interactions and there is a general agreement on the possibility that ground state superradiance can occur in the presence of magnetic interactions [5, 6]. Recent no-go theorems have provided rather general demonstrations that gauge invariance forbids any phase transition to a photon condensate state when the cavity-photon mode is assumed to be spatially uniform in the region where the dipoles are located [4, 7]. On the other hand, a number of papers still support the existence of a SPT in many-dipole cavity-QED systems (e.g., [8, 9, 10]). I present a brief historical account of this long standing debate and try to identify the origin of the fundamental errors determining the prediction of the SPT in many-dipole systems.
References
[1] M. Bamba and T. Ogawa, Phys. Rev. A, vol. 90, p. 063825, Dec 2014.
[2] L. Garziano, A. Settineri, O. Di Stefano, S. Savasta, and F. Nori, Phys. Rev. A, vol. 102, p. 023718, Aug 2020.
[3] J. M. Knight, Y. Aharonov, and G. T. C. Hsieh, Phys. Rev. A, vol. 17, pp. 1454–1462, Apr 1978.
[4] G. M. Andolina, F. M. D. Pellegrino, V. Giovannetti, A. H. MacDonald, and M. Polini, Phys. Rev. B, vol. 100, p. 121109, Sep 2019.
[5] G. Andolina, F. Pellegrino, V. Giovannetti, A. MacDonald, and M. Polini, Phys. Rev. B, vol. 102, p. 125137, Sep 2020.
[6] J. Rom´an-Roche, F. Luis, and D. Zueco, Phys. Rev. Lett., vol. 127, p. 167201, Oct 2021.
[7] G. Andolina, F. Pellegrino, A. Mercurio, O. Di Stefano, M. Polini, and S. Savasta, The European Physical Journal Plus, vol. 137, p. 1, Dec 2022. 1