arXiv subjects

Paolo Di Porto

Publications and source records attributed to Paolo Di Porto.

6 recordsLinked to original sources

arXiv2025

The microscopic origin of the Quantum Hall Effect

Topology is key in describing unconventional quantum phases of matter and devising robust quantum technology. Exactly how topology mixes with quantum mechanics remains largely unclear, as testified by the lack of a unifying microscopic theory for the ever-expanding and still puzzling transport behavior of electrons in the Quantum Hall Effect. Here we formulate a microscopic theory able to quantitatively describe the large wealth of Quantum Hall physics starting from one basic assumption, that the topological constraint in actual space leads to a superposition of states in the associated angular space. This allows us to identify the mechanism underlying quantum topology, single-particle wavefunction regularity in 3D, while many-body physics and disorder play no fundamental role. Our findings introduce a new far-reaching perspective in analyzing topological quantum systems and applications, such as topological quantum computing.

cond-mat.mes-hall↗

arXiv2021

Constraint-free wavelength conversion supported by giant optical refraction in a 3D perovskite supercrystal

Nonlinear response in a material increases with its index of refraction as $n^4$. Commonly, $n \sim$ 1 so that diffraction, dispersion, and chromatic walk-off limit nonlinear scattering. Ferroelectric crystals with a periodic 3D polarization structure overcome some of these constraints through versatile Cherenkov and quasi-phase-matching mechanisms. Three-dimensional self-structuring can also lead to a giant optical refraction. Here, we perform second-harmonic-generation experiments in KTN:Li in conditions of giant broadband refraction. Enhanced response causes wavelength conversion to occur in the form of bulk Cherenkov radiation without diffraction and chromatic walk-off, even in the presence of strong wave-vector mismatch and highly focused beams. The process occurs with a wide spectral acceptance of more than 100 nm in the near infrared spectrum, an ultra-wide angular acceptance of up to $\pm 40^{\circ}$, with no polarization selectivity, and can be tuned to allow bulk supercontinuum generation. Results pave the way to highly efficient and adaptable nonlinear optical devices with the promise of single-photon-to-single-photon nonlinear optics.

physics.optics↗

arXiv2006

Dynamics of a diathermal versus an adiabatic piston in an ideal gas: Langevin's and phase-space approaches

We present a comparison between the random motion of an adiabatic and a diathermal piston sliding in a perfect gas. In particular, their dynamical behaviour, if investigated by means of Langevin's approach, shows the amplitude of the adiabatic-piston random displacements around the equilibrium position to be much larger (by a factor (M/m)^(1/2), where M and m are the piston mass and the mass of the single gas molecule) than that of the diathermal piston. The origin of this intriguing difference, which is accounted for in the frame of Langevin's approach, is also explored in terms of a space-phase analysis.

cond-mat.dis-nn↗

arXiv2006

Callen's Adiabatic Piston and the Limits of the Second Law of Thermodynamics

The limits of the Second Law of Thermodynamics, which reigns undisputed in the macroscopic world, are investigated at the mesoscopic level, corresponding to spatial dimensions of a few microns. An extremely simple isolated system, modeled after Callen's adiabatic piston, [1] can, under appropriate conditions, be described as a self-organizing Brownian motor and shown to exhibit a perpetuum mobile behavior.

physics.class-ph↗

arXiv2004

Perfect Optical Solitons: Spatial Kerr Solitons as Exact Solutions of Maxwell's Equations

We prove that spatial Kerr solitons, usually obtained in the frame of nonlinear Schroedinger equation valid in the paraxial approximation, can be found in a generalized form as exact solutions of Maxwell's equations. In particular, they are shown to exist, both in the bright and dark version, as linearly polarized exactly integrable one-dimensional solitons, and to reduce to the standard paraxial form in the limit of small intensities. In the two-dimensional case, they are shown to exist as azimuthally polarized circularly symmetric dark solitons. Both one and two-dimensional dark solitons exhibit a characteristic signature in that their asymptotic intensity cannot exceed a threshold value in correspondence of which their width reaches a minimum subwavelength value.

physics.optics↗

arXiv2004

Azimuthally polarized spatial dark solitons: exact solutions of Maxwell's equations in a Kerr medium

Spatial Kerr solitons, typically associated with the standard paraxial nonlinear Schroedinger equation, are shown to exist to all nonparaxial orders, as exact solutions of Maxwell's equations in the presence of vectorial Kerr effect. More precisely, we prove the existence of azimuthally polarized, spatial, dark soliton solutions of Maxwell's equations, while exact linearly polarized (2+1)-D solitons do not exist. Our ab initio approach predicts the existence of dark solitons up to an upper value of the maximum field amplitude, corresponding to a minimum soliton width of about one fourth of the wavelength.

physics.optics↗