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Kernels for non interacting fermions via a Green’s function approach with applications to step potentials

hal.structure.identifierLaboratoire Ondes et Matière d'Aquitaine [LOMA]
dc.contributor.authorDEAN, David
hal.structure.identifierChamps Aléatoires et Systèmes hors d'Équilibre
dc.contributor.authorDOUSSAL, Pierre Le
hal.structure.identifierLaboratoire de Physique Théorique et Modèles Statistiques [LPTMS]
dc.contributor.authorMAJUMDAR, Satya N.
hal.structure.identifierLaboratoire de Physique Théorique et Modèles Statistiques [LPTMS]
dc.contributor.authorSCHEHR, Grégory
hal.structure.identifierLaboratoire de Physique Théorique et Modèles Statistiques [LPTMS]
dc.contributor.authorSMITH, Naftali R.
dc.date.issued2021-02-05
dc.identifier.issn1751-8113
dc.description.abstractEnThe quantum correlations of $N$ noninteracting spinless fermions in their ground state can be expressed in terms of a two-point function called the kernel. Here we develop a general and compact method for computing the kernel in a general trapping potential in terms of the Green's function for the corresponding single particle Schr\"odinger equation. For smooth potentials the method allows a simple alternative derivation of the local density approximation for the density and of the sine kernel in the bulk part of the trap in the large $N$ limit. It also recovers the density and the kernel of the so-called {\em Airy gas} at the edge. This method allows to analyse the quantum correlations in the ground state when the potential has a singular part with a fast variation in space. For the square step barrier of height $V_0$, we derive explicit expressions for the density and for the kernel. For large Fermi energy $\mu>V_0$ it describes the interpolation between two regions of different densities in a Fermi gas, each described by a different sine kernel. Of particular interest is the {\em critical point} of the square well potential when $\mu=V_0$. In this critical case, while there is a macroscopic number of fermions in the lower part of the step potential, there is only a finite $O(1)$ number of fermions on the shoulder, and moreover this number is independent of $\mu$. In particular, the density exhibits an algebraic decay $\sim 1/x^2$, where $x$ is the distance from the jump. Furthermore, we show that the critical behaviour around $\mu = V_0$ exhibits universality with respect with the shape of the barrier. This is established (i) by an exact solution for a smooth barrier (the Woods-Saxon potential) and (ii) by establishing a general relation between the large distance behavior of the kernel and the scattering amplitudes of the single-particle wave-function.
dc.description.sponsorshipMatrices aléatoires et fermions piégés - ANR-17-CE30-0027
dc.language.isoen
dc.publisherIOP Publishing
dc.title.enKernels for non interacting fermions via a Green’s function approach with applications to step potentials
dc.typeArticle de revue
dc.identifier.doi10.1088/1751-8121/abd9ef
dc.subject.halPhysique [physics]
dc.identifier.arxiv2009.12882
bordeaux.journalJournal of Physics A: Mathematical and Theoretical
bordeaux.page084001
bordeaux.volume54
bordeaux.issue8
bordeaux.peerReviewedoui
hal.identifierhal-03177657
hal.version1
hal.popularnon
hal.audienceInternationale
hal.origin.linkhttps://hal.archives-ouvertes.fr//hal-03177657v1
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