Two problems in solid state physics and superconductivity are addressed by applications of dispersion dynamics. The first is the Hall effect. The dynamics of charges that yield positive Hall coefficients in material having no mobile positive charges have always been problematic The effect requires both electric and magnetic response, but magnetic deflection is only possible in mobile charges. In high temperature superconductors, these charges must be electrons. Contrary to Newton’s second law, their acceleration is reversed in crystal fields that dictate negative dispersion. This is evident in room temperature measurements, but a second problem arises in supercurrents at low temperatures. The charge dynamics in material having zero internal electric field because of zero resistivity; and zero magnetic field because of the Meissner-Ochsenfeld diamagnetism; while the supercurrents themselves have properties of zero net momentum; zero spin; and sometimes, zero charge; are so far from having been resolved that they may never have been addressed. Again, dispersion dynamics are developed to provide solutions given by reduction of the superconducting wave packet. The reduction is here physically analyzed, though it is usually treated as a quantized unobservable.
Two problems in solid state physics and superconductivity are addressed by applications of dispersion dynamics. The first is the Hall effect. The dynamics of charges that yield positive Hall coefficients in material having no mobile positive charges have always been problematic The effect requires both electric and magnetic response, but magnetic deflection is only possible in mobile charges. In high temperature superconductors, these charges must be electrons. Contrary to Newton’s second law, their acceleration is reversed in crystal fields that dictate negative dispersion. This is evident in room temperature measurements, but a second problem arises in supercurrents at low temperatures. The charge dynamics in material having zero internal electric field because of zero resistivity; and zero magnetic field because of the Meissner-Ochsenfeld diamagnetism; while the supercurrents themselves have properties of zero net momentum; zero spin; and sometimes, zero charge; are so far from having been resolved that they may never have been addressed. Again, dispersion dynamics are developed to provide solutions given by reduction of the superconducting wave packet. The reduction is here physically analyzed, though it is usually treated as a quantized unobservable.
Recent numerical calculation of the intrinsic thermal Hall conductivity of nodal d-wave superconductors in the mixed state revealed a rapid increase of this quantity above an onset temperature. Interestingly, this defines a measurable energy scale in an otherwise gapless state. Using the mathematics of magnetic coherent states, in this paper such energy scale is related to a dynamical process associated with the Andreev scattering of an electron wave packet moving along the constant energy contours in the momentum space. This energy scale is then used to obtain an improved scaling collapse of numerically calculated thermal Hall conductivity in a tight-binding model as a function of temperature, magnetic field, and the d-wave pairing amplitude at various band fillings. The results indicate that the mentioned onset temperature is associated with the ability of the quasiparticle wave packet to complete its semiclassical orbit before it is appreciably scattered by the superconducting condensate.
The Meissner effect is a hallmark of superconductivity arising from the interplay between charged superfluids and electromagnetic fields. However, superfluidity can also occur in systems of charge-neutral particles with magnetic or electric dipole moments, such as Bose-Einstein condensates of magnons or excitons. Despite this interest, the electromagnetic response of dipole superfluids, including potential analogues or contrasts to the Meissner effect, remains poorly understood. Here we develop a Ginzburg-Landau theory to describe dipole superfluids subjected to a pseudo-magnetic field, which is induced by a spatially modulating electromagnetic field. In magnetic dipole superfluids, the response differs strikingly from the conventional Meissner effect: the external field is enhanced by a positive feedback, forming a vortex lattice separated by singular domain walls with diverging electric charges. In contrast, electric dipole superfluids exhibit screening akin to superconductors, where the pseudo-magnetic field is suppressed except near vortices. The electromagnetic response of dipole superfluids, including potential analogues to the Meissner effect, remains poorly understood. This paper develops a phenomenological theory and shows that magnetic-dipole superfluids form vortex lattices separated by singular domain walls with concentrated electric charge, while electric-dipole superfluids exhibit vortex lattices resembling those in conventional superconductors.
Abstract Within the past decade there has been a resurgence of interest in the dynamics of superfluid and superconducting vortices. One source of motivation for this topic may be attributed to the discovery of the quantum Hall effect (von Klitzing et al., 1980), which led to the suggestion that elementary excitations in 2D systems may obey nonstandard statistics (Wilczek, 1982; Halperin, 1984). Haldane and Wu (1985) pointed out a powerful analogy between the dynamics of a vortex in a 2D superfluid film and the electron motion in a cyclotron orbit. critical value.
In this paper we investigate the zero-temperature doping-driven evolution of a superconductor toward the Mott insulator in a two-dimensional electron model, relevant for high-temperature superconductivity. To this purpose we use a cluster extension of dynamical mean-field theory. Our results show that a standard d-wave superconductor, realized at high doping, is driven into the Mott insulator via an intermediate superconducting state displaying unconventional physical properties. By restoring the translational invariance of the lattice, we give an interpretation of these findings in momentum space. In particular, we show that at a finite doping a strong momentum-space differentiation takes place: non-Fermi liquid and insulatinglike (pseudogap) characters rise in some regions (antinodes), while Fermi liquid quasiparticles survive in other regions (nodes) of momentum space. We describe the consequence of these happenings on the spectral properties, stressing in particular the behavior of the superconducting gap, which reveals two distinct nodal and antinodal energy scales as a function of doping, detected in photoemission and Raman spectroscopy experiments. We study and compare with experimental results the doping-dependent behavior of other physical quantities, such as for instance, the nodal quasiparticle velocity (extracted in angle-resolved photoemission) and the low-energy slopes of the local density of states and of the Raman scattering response. We then propose a description of the evolution of the electronic structure while approaching the Mott transition. We show that, within our formalism, a strong asymmetry naturally arises in the local density of states, measured in scanning tunneling spectroscopy. We investigate in detail the doping evolution of the electronic bands, focusing on the kinklike quasiparticle dispersion observed with angle-resolved photoemission in specific cuts of the momentum-energy space. We finally show the consequences of the properties presented above in the doping dependence of the Hall resistivity, measured in magnetotransport experiments.
Die Entwicklung einer einheitlichen Theorie für Quantenmechanik und Gravitation ist derzeitig eines der größten Ziele der Physik. Ein hohes Hindernis, dass es dabei zu überwinden gibt, ist der Mangel an Experimenten - um experimentelle Daten in diesem Bereich zu gewinnen, ist es nötig, die Bewegungsfreiheitsgrade eines massiven Teilchens in einen Quantenzustand zu versetzen. Der aktuelle Stand der Technik ermöglicht es, das Gravitationsfeld von Milligramm-Massen zu messen und optisch levitierte Teilchen mit Femtogramm-Massen in einen Quantenzustand zu versetzen. Die magnetische Levitation von supraleitenden Teilchen in einem quasistatischen Feld kann nahezu dämpfungsfrei sein, und zwar selbst für massive Teilchen, deren Gravitationsfeld experimentell nachweisbar ist. Die Bewegung dieser Teilchen kann über das Magnetfeld beeinflusst und prinzipiell in einen Quantenzustand versetzt werden. In dieser Arbeit habe ich das Fundament für Experimente mit levitierenden Supraleitern gelegt. Ich habe das Verhalten von supraleitenden Teilchen in einem Magnetfeld sowohl analytisch als auch numerisch berechnet und, basierend auf den Ergebnissen, eine magnetische Falle für Supraleiter entworfen. Ich habe die Falle in einen Entmischkryostaten bei 15mK eingebaut und damit eine supraleitende Kugel mit einem Durchmesser von 100um levitiert. Ich konnte die Bewegung der Kugel mit einem supraleitenden Quanteninterferenzgerät auslesen und einen Gütefaktor von 2.6e7 nachweisen. Durch Echtzeitverarbeitung des gemessenen Signals und einer darauf basierenden Modifikation des Magnetfelds konnte ich die Bewegung des Teilchens in allen drei Dimensionen kontrollieren. Weiters habe ich noch ein neuartiges kryogenens Vibrationisolationssystem entworfen und eingebaut, sowie Magnetschilder zur Abschirmung vor externen Magnetfeldschwankungen. Eine detaillierte Analyse der Ergebnisse zeigt, dass es mit weiteren Verbesserungen möglich ist, das levitierte Teilchen in einen Quantenzustand zu versetzen. Dadurch hat dieses System das Potential, Quantenphysik mit massiven, makroskopischen Teilchen zu betreiben und Gravitationseffekte in diesem Bereich zu testen.
We propose a simple setup for introducing an artificial magnetic field for neutral atoms in 2D optical lattices. This setup is based on the phenomenon of photon-assistent tunneling and involves a low-frequency periodic driving of the optical lattice. We also address the problem of detecting this effective magnetic field. In particular, we discuss interference patterns of the atomic wave function and study the center of mass wave-packet dynamics, which shows some features of cyclotron dynamics of a classical charged particle. Introduction. – A major motivation of current research with cold atoms in optical lattices is the prospect of simulating the solid state physics. However, to have a full access to phenomena of the solid state physics this system (which can be considered as an artificial crystal) should be accomplished by artificial electric and magnetic fields. In present days experiments the former case of external electric field is routinely mimicked by accelerating the optical lattice [1–3], or by using the gravitational force [4–6] or a combination of gravitational and levitational forces [7]. The case of magnetic field is more difficult for laboratory realization because it requires a setup, where atomic wave function acquires a finite phase when the atom tunnels along a closed path on the lattice. This setup was suggested in the seminal paper [8], where the authors use two independent 2D optical lattices for two different internal atomic states, which are coupled by additional Raman lasers. The Rabi transition between internal states induces hopping of the atom between nearest lattice sites, where the required phase accumulation is achieved by using a special geometry for the Raman beams. This idea was developed further in Ref. [9, 10]. It was shown that one can also introduce an exotic (unphysical) field and non-Abelian gauge potentials by using the Raman-laser technique. For atoms in a harmonic trap (no lattice) the Raman scheme with 3 spin states of the F = 1 electronic ground state of Rb atom was realized in the recent experiment [11]. In this setup the magnitude of the effective magnetic field is defined by the gradient of the real magnetic field which splits the F = 1 level into Zeeman sublevels. In the paper the authors put forward a conjecture that this scheme should work in the presence of an optical lattice as well. We note that the cited experiment also illuminated a drawback of the Raman-laser based techniques. Namely, the spontaneous emission from the Raman beams removes atom from the trap, causing the population to decay within approx. 2 seconds.