Giant Atom Eats Quantum Gas
Oct. 31, 2013 — A team of
experimental and theoretical physicists from the University of Stuttgart
studied a single micrometer-sized atom. This atom contains tens of
thousands of normal atoms in its electron orbital
.
Illustration
of the system investigated: A highly excited Rydberg-atom, consisting
of a single electron (blue), traveling on a large orbit far from the
positively charged core (red). The Rydberg atom has the same spatial
extent as the ultracold atomic cloud. The single electron is exciting
oscillations, so-called phonons, in the surrounding quantum gas.
(Credit: Image courtesy of University of Stuttgart)
The interaction of electrons and matter is fundamental to material
properties such as electrical conductivity. Electrons are scattering
from atoms of the surrounding matter and can excite lattice
oscillations, so called phonons, thereby transferring energy to the
environment. The electron is therefore slowed which causes electrical
resistance. However, in certain materials phonons can surprisingly cause
the opposite effect, so-called superconductivity, where the electrical
resistance drops to zero. Understanding the interaction of electrons and
matter is therefore important goal in order to both answer fundamental
questions as well as to solve technical problems.
A single electron is best suited for systematic investigations of such processes. For the first time, physicists from Stuttgart have now realized a model system in the laboratory, where the interaction of a single electron with many atoms inside its orbital can be studied. These atoms are from an ultracold cloud near absolute zero, a so-called Bose-Einstein condensate.
The basic idea now is simple: Instead of using a technically challenging electron trap, the scientists are using the fact that in nature electrons are bound to a positively charged atomic core. In a classical picture, they are travelling on ellipsoidal orbits around the core. These orbits are usually very small, typically in the range below one nanometer. In order to achieve an interaction between an electron and many atoms, an atom is excited from a cloud consisting of 100,000 atoms using laser light. The orbit of a single electron then expands to several micrometers and a Rydberg atom is formed. On atomic length scales, this atom is huge, larger than most bacteria, which are consisting each of several billions to trillions of atoms. The Rydberg atom then contains tens of thousands of atoms from the cold cloud. Thus, the electron is trapped in a defined volume and at the same time interacts with a large number of atoms. This interaction is so strong that the whole atomic cloud, consisting of 100,000 atoms is considerably influenced by the single electron. Depending on its quantum state the electron excites phonons in the atomic cloud, which can be measured as collective oscillations of the whole cloud culminating in a loss of atoms from the trap.
The experimental observations in the group of Prof. Tilman Pfau could so far largely be explained by collaborative work with the theory group of Prof. Hans Peter Büchler. However, this work is only the basis for a series of further exciting experiments. According to the previous studies an electron is leaving a clear trace in the surrounding atomic cloud. Therefore imaging a single electron in a well defined quantum state seems to be feasible.
This work has been realized within Sonderforschungsbereich SFB/TRR 21 (Control of quantum correlations in tailored matter) and has been supported by the Detusche Forschungsgemeinschaft DFG and the European Research Council. These results have been published in the journal Nature.
A single electron is best suited for systematic investigations of such processes. For the first time, physicists from Stuttgart have now realized a model system in the laboratory, where the interaction of a single electron with many atoms inside its orbital can be studied. These atoms are from an ultracold cloud near absolute zero, a so-called Bose-Einstein condensate.
The basic idea now is simple: Instead of using a technically challenging electron trap, the scientists are using the fact that in nature electrons are bound to a positively charged atomic core. In a classical picture, they are travelling on ellipsoidal orbits around the core. These orbits are usually very small, typically in the range below one nanometer. In order to achieve an interaction between an electron and many atoms, an atom is excited from a cloud consisting of 100,000 atoms using laser light. The orbit of a single electron then expands to several micrometers and a Rydberg atom is formed. On atomic length scales, this atom is huge, larger than most bacteria, which are consisting each of several billions to trillions of atoms. The Rydberg atom then contains tens of thousands of atoms from the cold cloud. Thus, the electron is trapped in a defined volume and at the same time interacts with a large number of atoms. This interaction is so strong that the whole atomic cloud, consisting of 100,000 atoms is considerably influenced by the single electron. Depending on its quantum state the electron excites phonons in the atomic cloud, which can be measured as collective oscillations of the whole cloud culminating in a loss of atoms from the trap.
The experimental observations in the group of Prof. Tilman Pfau could so far largely be explained by collaborative work with the theory group of Prof. Hans Peter Büchler. However, this work is only the basis for a series of further exciting experiments. According to the previous studies an electron is leaving a clear trace in the surrounding atomic cloud. Therefore imaging a single electron in a well defined quantum state seems to be feasible.
This work has been realized within Sonderforschungsbereich SFB/TRR 21 (Control of quantum correlations in tailored matter) and has been supported by the Detusche Forschungsgemeinschaft DFG and the European Research Council. These results have been published in the journal Nature.
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