Charge-dipole interactions are very common interactions among atoms and molecules, especially materials that can emit light or contain free charges. The second-order charge-dipole interactions, proportional to $\frac{1}{R^4}$, are stronger than the second-order dipole-dipole interactions or van der Waals interactions, proportional to $\frac{1}{R^6}$, at longer distances. In reality, there is more than one atom or charge; therefore, we focus on few-body charge-dipole interactions, such as charge-dipole-dipole interactions. Laser cooling and trapping allow us to study such interactions with much higher precision. In this article, charge-dipole interactions will be investigated in ultracold gases. To increase the interaction strength, we excite the ultracold atoms to highly excited states, Rydberg states. Here, we treat one Rydberg atom as a dipole, the excited electron and the ion core are the two poles of an electric dipole. Specifically, we study charge-atom interactions in ultracold Rydberg gases.
Charge-dipole interactions are very common interactions among atoms and molecules, especially materials that can emit light or contain free charges. The second-order charge-dipole interactions, proportional to R41, are stronger than the second-order dipole-dipole interactions or van der Waals interactions, proportional to R61, at longer distances. In reality, there is more than one atom or charge; therefore, we focus on few-body charge-dipole interactions, such as charge-dipole-dipole interactions. Laser cooling and trapping allow us to study such interactions with much higher precision. In this article, charge-dipole interactions will be investigated in ultracold gases. To increase the interaction strength, we excite the ultracold atoms to highly excited states, Rydberg states. Here, we treat one Rydberg atom as a dipole, the excited electron and the ion core are the two poles of an electric dipole. Specifically, we study charge-atom interactions in ultracold Rydberg gases.
Charge-dipole interactions are very common interactions among atoms and molecules, especially materials that can emit light or contain free charges. The second-order charge-dipole interactions, proportional to 1 R 4 , are stronger than the second-order dipole-dipole interactions or van der Waals interactions, proportional to 1 R 6 , at longer distances. In reality, there is more than one atom or charge; therefore, we focus on few-body charge-dipole interactions, such as charge-dipole-dipole interactions. Laser cooling and trapping allow us to study such interactions with much higher precision. In this article, charge-dipole interactions will be investigated in cold gases. To increase the interaction strength, we excite the cold atoms to highly excited states, Rydberg states. Here, we treat one Rydberg atom as a dipole; the excited electron and the ion core are the two poles of an electric dipole. Specifically, we study charge-atom interactions in cold Rydberg gases. The laser-cooled lower level atoms were excited to highly excited states, and we scanned a microwave to look at the line shape of a particular transition between two Rydberg states. It has been shown that adding a charge can enhance atom-atom interactions under certain circumstances.
Van der Waals interactions are interactions between dipoles. Similarly, quadrupole-quadrupole interactions are interactions between quadrupoles. In this article, we focus on the interactions between two dipoles or two quadrupoles. Classically, we treat one Rydberg atom as a dipole; an outer excited electron and an ion core are the two poles of a dipole. Quantum mechanically, we consider Rydberg transition dipoles. Therefore, dipole-dipole interactions are the interactions between two Rydberg atoms. Rydberg atoms have quadrupole components; consequently, the interactions between two Rydberg atoms have quadrupole-quadrupole interaction components. In this article, we examine the dipole-dipole and quadrupole-quadrupole contribution to the interactions between ultracold Rydberg atoms. It is shown that the evidence of quadrupole-blockade has been observed, which is essential for fabricating more compact quantum computers, quantum electronics, as well as quantum sensing.
Few-body interactions offer the opportunity to study the isolated atom to few-body coupled molecules, and to condensed matter transitions. Atoms in molecules and in condensed matters are coupled by different orders of multipole–multipole interactions, which all stem from different orders of approximations from coulomb interactions between multiple charges. The lowest order multipole–multipole interaction is the dipole–dipole interaction, which is proportional to the size of the dipole. In this article, we use Rydberg atoms, which have more than 1000 times greater electric dipoles than the ground state atoms, to study the van der Waals interaction between few bodies. In addition to the large dipoles, the kinetic energy of the atoms is significantly reduced by reducing the temperature, which makes these interactions stable and observable. Here, we report on the 2D and 3D few-body interaction potentials and possible ways of creating semistable molecules in such an ultracold Rydberg gas with a temperature of ≈100 nK. Although we use Rydberg atoms in this article, this calculation can be applied to other states too. The results reported here are useful for studying repulsive van der Waals interactions and creating ultracold molecules.
Abstract The interactions between dipoles are called dipole–dipole interactions. One type of dipole–dipole interaction is van der Waals interaction. Similar to van der Waals interactions, the interactions between quadrupoles are called quadrupole–quadrupole interactions. Atoms can be treated not only as dipoles but also as quadrupoles. In this article, we study the quadrupole interactions between highly excited atoms or Rydberg atoms. In addition, unlike many other calculations, in which the primary focus was on the one-dimensional two-body quadrupole–quadrupole interactions, the primary aim of this article is to study the two-dimensional few-body quadrupole–quadrupole interactions. Specifically, the two-dimensional three-body interactions are investigated. This research has many applications, such as quadrupole-blockade for quantum computing, creating molecules based on quadrupole interactions, or quadrupole–quadrupole molecules.
Abstract Many light-emitting objects, such as gases, have free charges or ions, and atoms are building blocks of those objects. Therefore, there are charge-atom interactions in those objects. A better understanding of charge-atom interactions will help to understand such objects. Among those objects, many atoms are in excited states, which causes light to be emitted. Highly excited states are called Rydberg states. In this article, we study the few-body charge-atom interactions of two-dimensional configurations, or planar Rydberg-atom/charge geometries. Specifically, we study one positive charge and two atoms, three atoms, four atoms, and five atoms lying on the same plane. In addition, we assume those atoms are in excited states, Rydberg states. Moreover, we investigate the principal quantum number dependence of such interactions. It has been shown that the maximum frequency shift of the n s n s n s + states is proportional to n 6 for an energy level in a certain principal quantum number range. Furthermore, we study the 1 R 2 dependent charge-atom interactions, where R is the distance between one atom and the positive charge.
Interactions between particles play an important role in quantum degenerate gases.\nIn fact, the system’s behavior is usually largely determined by the strength, range, and\nsymmetry of the interactions, even if very weak. For more than two decades after the\nfirst experimental realization of a Bose-Einstein condensate (BEC) in 1995, investigations of ultracold atomic gases have mainly considered contact-type interactions, which\nmodel the short-range van der Waals interactions between the atoms in terms of a single\nparameter, the s-wave scattering length. However, some atomic or molecules species\npossess a magnetic or electric dipole moment and additionally interact among each\nother via the dipole-dipole interaction (DDI), which is long-ranged and anisotropic.\nSignatures of the DDI have been first observed in a BEC of chromium atoms in 2005.\nIn the last several years, a new class of atoms from the lanthanide series, e.g., dysprosium and erbium, with stronger dipolar properties, have come into play. This permits\na more full-fledged study of dipolar effects in BECs. Furthermore, ultracold molecules\nand highly excited Rydberg atoms are other promising examples for futures studies of\nsystems where dipolar interaction will be even more dominant, but they still need experimental efforts to achieve the desired quantum regime. Whereas the weak DDI in a\nchromium BEC is well described with the Gross-Pitaevskii equation, stronger dipolar\ninteractions certainly necessitate a beyond-mean-field description within a Bogoliubov\ntheory.\nIn parallel to research on bosons, cold fermions also trigger great interest because\nthey are actually often found in nature, e.g., within the electron gas of metals, as\nneutrons of heavy stars, or as quarks in plasmas as constituent elements of composite particles. Contrary to Bose systems, quantum degeneracy in experiments is much\nmore difficult to achieve in Fermi systems, since s-wave scattering is absent between\nidentical fermions, due to the Pauli exclusion principle. It was first achieved in 1999\nfor alkali atoms using a technique based on the sympathetic cooling with a second spin\nstate, another species, or a different isotope. For highly magnetic atoms, quantum degeneracy was achieved for dysprosium in 2012 using the standard sympathetic cooling\ntechnique, while in 2014 erbium was cooled deep into the degenerate regime using a\ndirect evaporative cooling mediated by dipolar collisions. This direct cooling scheme\nivallows producing very dense Fermi gas down to 10% of the Fermi temperature.\nFurthermore, a novel kind of strongly dipolar quantum gases became available in\nthe last several years. These are weakly bound polar molecules produced from atoms\nwith large magnetic dipole moments, such as erbium. Only very recently a quantum\ndegenerate dipolar Fermi gas of potassium-rubidium molecules has been experimentally realized. Unlike previously considered magnetic systems, heteronuclear molecules\nsuch as potassium-rubidium possess large electric dipole moments. The next natural\nstep is to polarize this system in a preferential direction by an external electric field,\nsuch that the DDI dominates the behavior of the system, which would open up the\nrealm for experimental investigation of strong dipolar Fermi gases...