title: Experimental evidence of replica symmetry breaking in random lasers.
abstract: Spin-glass theory is one of the leading paradigms of complex physics and describes condensed matter, neural networks and biological systems, ultracold atoms, random photonics and many other research fields. According to this theory, identical systems under identical conditions may reach different states. This effect is known as replica symmetry breaking and is revealed by the shape of the probability distribution function of an order parameter named the Parisi overlap. However, a direct experimental evidence in any field of research is still missing. Here we investigate pulse-to-pulse fluctuations in random lasers, we introduce and measure the analogue of the Parisi overlap in independent experimental realizations of the same disordered sample, and we find that the distribution function yields evidence of a transition to a glassy light phase compatible with a replica symmetry breaking.
authors.affiliation: 1] Institute for Chemical Physical Processes, CNR (CNR-IPCF), UOS Roma Kerberos, Dept. of Physics, La Sapienza University, Piazzale Aldo Moro 5, I-00185 Rome, Italy [2] Department of Physics, La Sapienza University, Piazzale Aldo Moro 5, I-00185 Rome, Italy [3] Institute for Complex Systems, CNR (CNR-ISC), Via dei Taurini 19, I-00185 Rome, Italy.
authors.forename: N
authors.initials: N
authors.lastname: Ghofraniha
authors.affiliation: 1] Department of Physics, La Sapienza University, Piazzale Aldo Moro 5, I-00185 Rome, Italy [2] National Nanotechnology Laboratory of CNR-Nanoscience Institute (NNL, CNR-NANO), Via Arnesano, I-73100 Lecce, Italy.
authors.forename: I
authors.initials: I
authors.lastname: Viola
authors.affiliation: 1] Institute of Organic Synthesis and Photoreactivity, CNR (CNR-ISOF), Via Piero Gobetti 101, I-40129 Bologna, Italy [2] MIST.E-R Laboratory, Via Piero Gobetti 101, I-40129 Bologna, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Di Maria
authors.affiliation: Institute of Organic Synthesis and Photoreactivity, CNR (CNR-ISOF), Via Piero Gobetti 101, I-40129 Bologna, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Barbarella
authors.affiliation: 1] National Nanotechnology Laboratory of CNR-Nanoscience Institute (NNL, CNR-NANO), Via Arnesano, I-73100 Lecce, Italy [2] Department of Mathematics and Physics "Ennio de Giorgi", Salento University, Via Arnesano, I-73100 Lecce, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Gigli
authors.affiliation: 1] Institute for Chemical Physical Processes, CNR (CNR-IPCF), UOS Roma Kerberos, Dept. of Physics, La Sapienza University, Piazzale Aldo Moro 5, I-00185 Rome, Italy [2] Department of Physics, La Sapienza University, Piazzale Aldo Moro 5, I-00185 Rome, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Leuzzi
authors.affiliation: 1] Department of Physics, La Sapienza University, Piazzale Aldo Moro 5, I-00185 Rome, Italy [2] Institute for Complex Systems, CNR (CNR-ISC), Via dei Taurini 19, I-00185 Rome, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Conti