Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Physical Review A

Magneto-optical trapping of Fermionic potassium atoms

F. S. Cataliotti, Eric Cornell, C. Fort, M. Inguscio, Francesco Marin, M. Prevedelli, Leonardo Ricci, Guglielmo Maria Tino

Published Feb 1, 1998• 60 citations
Publisher

Abstract

We have trapped ${}^{40}\mathrm{K}$ in a vapor-cell magneto-optical trap starting from a natural abundance sample. This rare, weakly radioactive atom is a fermion. The number of trapped atoms is approximately 8000, with a density of $\ensuremath{\sim}{10}^{8}$ atoms/${\mathrm{cm}}^{3}$. Contrary to what is observed for the other isotopes of potassium, our data indicate that temperatures lower than the Doppler-cooling limit can be reached for ${}^{40}\mathrm{K}$. We discuss the interest of these results in view of possible experiments to study a degenerate Fermi gas.

DOI
10.1103/physreva.57.1136

Related papers

Sub-Doppler laser cooling and magnetic trapping of natural-abundance fermionic potassium

Mateusz Bocheński, Mariusz Semczuk

Abstract We demonstrate the largest number of 40K atoms that has ever been cooled to deeply sub-Doppler temperatures in a single-chamber apparatus without using an enriched source of potassium. With gray molasses cooling on the D 1-line following a standard D 2-line magneto-optical trap, we obtain 3 × 10 5 atoms at 10(2) µK. We reach densities high enough to measure the temperature via absorption imaging using the time-of-flight method. We magnetically trap a mixture of m F = − 3 / 2 , − 5 / 2 and − 7 / 2 Zeeman states of the F = 7 / 2 hyperfine ground state confining 5 × 10 4 atoms with a lifetime of 0.6 s or ∼ 10 3 atoms with a lifetime of 2.8 s—depending on whether the temperature of the potassium dispensers was chosen to maximize the atom number or the lifetime. The background pressure-limited lifetime of 0.6 s is a reasonable starting point for proof-of-principle experiments with atoms and/or molecules in optical tweezers as well as for sympathetic cooling with another species if transport to a secondary chamber is implemented. Our results show that unenriched potassium can be used to optimize experimental setups containing 40K in the initial stages of their construction, which can effectively extend the lifetime of enriched sources. Moreover, the demonstration of sub-Doppler cooling and magnetic trapping of a relatively small number of potassium atoms might influence experiments with laser-cooled radioactive isotopes of potassium.

arXiv:2307.16469•Journal of Physics B Atomic Molecular and Optical Physics•Jan 23, 2024•1 citation

Sub-Doppler laser cooling of fermionic 40K atoms

Giovanni Carlo Modugno, Craig Benko, Peter Hannaford +2 more

We report laser cooling of fermionic ${}^{40}\mathrm{K}$ atoms, with temperatures down to $(15\ifmmode\pm\else\textpm\fi{}5) \ensuremath{\mu}\mathrm{K},$ for an enriched sample trapped in a magneto-optical trap and additionaly cooled in optical molasses. This temperature is a factor of 10 below the Doppler-cooling limit and corresponds to an rms velocity within a factor of 2 of the lowest realizable rms velocity $(\ensuremath{\sim}{3.5v}_{\mathrm{rec}})$ in three-dimensional optical molasses. Realization of such low atom temperatures, up to now only accessible with evaporative cooling techniques, is an important precursor to producing a degenerate Fermi gas of ${}^{40}\mathrm{K}$ atoms.

arXiv:cond-mat/9908102•Physical Review A•Nov 1, 1999•32 citations

Efficient Capture in a vapor cell magneto-optical trap

Michelle S. Stephens, Royal Rhodes, Carl Wieman

Laser cooling and trapping of rare, radioactive isotopes has the potential for greatly enhancing experiments in high resolution spectroscopy of exotic species, electron electric-dipole moment searches, β-decay asymmetry, and parity nonconservation. The ability to hold atoms for several seconds at high densities (1011 cm-3) and away from the perturbing effects of the cell walls makes laser cooling and trapping attractive for use in the experiments mentioned above. Because many isotopes of interest for these experiments are difficult to produce, the ability to quickly and efficiently collect these atoms from a dilute vapor is crucial. We have demonstrated a 6% collection efficiency in a special wall-coated cell. We have developed a model that predicts the capture efficiency as a function of trap properties and have developed techniques for measuring the pertinent characteristics.

•May 8, 1994•0 citations

An enriched K40 source for fermionic atom studies

Brian DeMarco, H. Rohner, D. S. Jin

We have developed a novel, enriched potassium source for use in trapping and cooling of the fermionic isotope K40. The source is clean, easily controllable, and consistent with high vacuum applications. With this enriched source, we are able to collect 108 K40 atoms in a vapor cell magneto-optical trap.

Review of Scientific Instruments•Apr 1, 1999•42 citations

Low-temperature high-density magneto-optical trapping of potassium using the open 4S→5P transition at 405 nm

David C. McKay, Dylan Jervis, Daniel Fine +3 more

We report the laser cooling and trapping of neutral potassium on an open transition. Fermionic ${}^{40}$K is captured using a magneto-optical trap (MOT) on the closed $4{S}_{1/2}\ensuremath{\rightarrow}4{P}_{3/2}$ transition at 767 nm and then transferred, with high efficiency, to a MOT on the open $4{S}_{1/2}\ensuremath{\rightarrow}5{P}_{3/2}$ transition at 405 nm. Because the $5{P}_{3/2}$ state has a smaller linewidth than the $4{P}_{3/2}$ state, the Doppler limit is reduced from 145 \ensuremath{\mu}K to 24 \ensuremath{\mu}K, and we observe temperatures as low as 63(6) $\ensuremath{\mu}$K. The density of trapped atoms also increases, due to reduced temperature and reduced expulsive light forces. We measure a two-body loss coefficient of $\ensuremath{\beta}=1.4(1)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$ cm${}^{3}$/s near saturation intensity, and estimate an upper bound of $8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}18}$ cm${}^{2}$ for the ionization cross section of the $5P$ state at 405 nm. The combined temperature and density improvement in the 405 nm MOT is a twenty-fold increase in phase-space density over our 767 nm MOT, showing enhanced precooling for quantum gas experiments. A qualitatively similar enhancement is observed in a 405 nm MOT of bosonic ${}^{41}$K.

arXiv:1110.4067•Physical Review A•Dec 21, 2011•68 citations

Trapping fermionic potassium atoms in a quasi-electrostatic optical dipole potential

Alexandro Gatto

Ultracold quantum gases have become a frequently used tool for the investigation of a variety of physical issues within the last decade, ranging from general questions in quantum physics up to special topics, e.g. quantum simulations of the physical origin of high temperature superconductivity in condensed matter physics. In this thesis, experiments are presented on the creation of an ultracold quantum gas of the fermionic potassium isotope, 40K, by all-optical means. For this purpose, a new experimental setup was designed, which was started from the scratch, with the long term goal of creating a supersolid in an optical lattice. One focus of this work lies in identifying light-assisted losses as a main restriction for achieving higher 40K atom numbers in a magneto-optical trap and in identifying light-assisted losses as a main reason for a low atomic transfer efficiency from a magneto-optical trap into an optical, quasi-electrostatic dipole trap (further called optical dipole trap) for 40K atoms. Naturally, another focus of this work lies in the application of different techniques to reduce these from light-assisted losses dependent restrictions. A two-dimensional magneto-optical trap, located in the prechamber of a vacuum system, creates a continuous beam of 40K atoms. The atoms of this beam are recaptured in the main chamber of the vacuum system by a spatial dark spot magneto-optical trap. Here, a dark magneto-optical trap is implemented instead of a standard magneto-optical trap in order to reduce light-assisted losses. Up to 1x109 atoms at temperatures around 240 μK are trapped in the dark magneto-optical trap. This is a factor of ten higher compared to atom numbers of a 40K standard magneto-optical trap. The light-assisted losses in the 40K magneto-optical trap were measured as a function of the total trapping intensity and as a function of the repumping intensity. In both cases, the smallest observed loss coefficient was β ≈ 2.5x10-10 cm3/s. Compared to the smallest values of β of all other alkali elements (apart from the bosonic potassium isotopes), the light-assisted losses with 40K atoms are approximately two orders of magnitude larger. Up to 6x105 atoms were transferred from the spatial dark magneto-optical trap into the quasi-electrostatic dipole trap, which was created by using the trapping potential induced by radiation emitted by a CO2 laser operating at a wavelength near 10.6 μm. In order to reach the here reported atom numbers in the optical dipole trap, its trapping volume had to be increased in comparison to a simple dipole trap arrangement as induced with a single focused dipole trapping beam. Simultaneously, the strong confinement, as present in a tigthly focused single beam trap and as required for a subsequent evaporative cooling, had to be maintained. For this purpose, the trapping laser beam of the optical dipole trap was retroreflected in such a way that an overall optical dipole trap with a nearly doubled waist and a slightly deeper potential depth was created. By this trapping arrangement, the number of atoms confined in the optical dipole trap could be nearly doubled compared to a simple dipole trapping arrangement consisting of a single tightly focused trapping beam. The atomic transfer process itself, from the magneto-optical trap into the optical dipole trap, was organized in two steps. In a first step, the dark magneto-optical trap was transformed into a compressed magneto-optical trap by increasing the field gradient and bringing the cooling laser closer to resonance as compared to the detuning of the usual magneto-optical trap. In contrast to other experiments, the repumping laser of the magneto-optical trap was detuned to the blue of the used repumping transition. As a consequence, atoms were optically pumped into the upper hyperfine ground state |S1/2, F=7/2〉, realizing a temporal dark, compressed magneto-optical trap in analogy to the operation of a temporal dark magneto-optical trap. By this approach, light-assisted losses were reduced. In the second step of the transfer process, the light fields of the magneto-optical trap and the optical dipole trap were alternately switched on and off. In this way, a spatially inhomogeneous ac Stark shift of the cooling transitions due to the spatially inhomogeneous intensity distribution of the dipole trapping beam was avoided and again light-assisted losses were reduced during the loading phase of atoms from the compressed magneto-optical trap into the optical dipole trap. The loading rate was measured to be approximately 2.8x108 atoms/s. The light-assisted losses during loading of the optical dipole trap were determined to be β ≈ 4.8x10-10 cm3/s. In the final step of the experiment, the temperature of the atomic ensemble confined in the optical dipole trap was further reduced by evaporative cooling. After an evaporation time of about 30 s, temperatures of 140 nK were reached at typical atom numbers of 12000. The corresponding Fermi temperature is TF = 110 nK yielding a ratio T/TF ≈ 1.3 which indicates that the fermionic potassium atoms are cooled close to the onset of quantum degeneracy. In the future, an additional trapping and evaporative cooling step within a magnetic quadrupole trap should allow for an improved loading efficiency into the far detuned optical dipole trap and finally allow for a subsequent evaporative cooling to a quantum degenerate Fermi gas.

•Aug 3, 2012•0 citations
We have trapped 40K{}^{40}\mathrm{K}40K in a vapor-cell magneto-optical trap starting from a natural abundance sample. This rare, weakly radioactive atom is a fermion. The number of trapped atoms is approximately 8000, with a density of \ensuremath∼108\ensuremath{\sim}{10}^{8}\ensuremath∼108 atoms/cm3{\mathrm{cm}}^{3}cm3. Contrary to what is observed for the other isotopes of potassium, our data indicate that temperatures lower than the Doppler-cooling limit can be reached for 40K{}^{40}\mathrm{K}40K. We discuss the interest of these results in view of possible experiments to study a degenerate Fermi gas.
Abstract We demonstrate the largest number of 40K atoms that has ever been cooled to deeply sub-Doppler temperatures in a single-chamber apparatus without using an enriched source of potassium. With gray molasses cooling on the D 1-line following a standard D 2-line magneto-optical trap, we obtain 3 × 10 5 atoms at 10(2) µK. We reach densities high enough to measure the temperature via absorption imaging using the time-of-flight method. We magnetically trap a mixture of m F = − 3 / 2 , − 5 / 2 and − 7 / 2 Zeeman states of the F = 7 / 2 hyperfine ground state confining 5 × 10 4 atoms with a lifetime of 0.6 s or ∼ 10 3 atoms with a lifetime of 2.8 s—depending on whether the temperature of the potassium dispensers was chosen to maximize the atom number or the lifetime. The background pressure-limited lifetime of 0.6 s is a reasonable starting point for proof-of-principle experiments with atoms and/or molecules in optical tweezers as well as for sympathetic cooling with another species if transport to a secondary chamber is implemented. Our results show that unenriched potassium can be used to optimize experimental setups containing 40K in the initial stages of their construction, which can effectively extend the lifetime of enriched sources. Moreover, the demonstration of sub-Doppler cooling and magnetic trapping of a relatively small number of potassium atoms might influence experiments with laser-cooled radioactive isotopes of potassium.
We report laser cooling of fermionic 40K{}^{40}\mathrm{K}40K atoms, with temperatures down to $(15\ifmmode\pm\else\textpm\fi{}5) \ensuremath{\mu}\mathrm{K},$ for an enriched sample trapped in a magneto-optical trap and additionaly cooled in optical molasses. This temperature is a factor of 10 below the Doppler-cooling limit and corresponds to an rms velocity within a factor of 2 of the lowest realizable rms velocity $(\ensuremath{\sim}{3.5v}_{\mathrm{rec}})$ in three-dimensional optical molasses. Realization of such low atom temperatures, up to now only accessible with evaporative cooling techniques, is an important precursor to producing a degenerate Fermi gas of 40K{}^{40}\mathrm{K}40K atoms.
Laser cooling and trapping of rare, radioactive isotopes has the potential for greatly enhancing experiments in high resolution spectroscopy of exotic species, electron electric-dipole moment searches, β-decay asymmetry, and parity nonconservation. The ability to hold atoms for several seconds at high densities (1011 cm-3) and away from the perturbing effects of the cell walls makes laser cooling and trapping attractive for use in the experiments mentioned above. Because many isotopes of interest for these experiments are difficult to produce, the ability to quickly and efficiently collect these atoms from a dilute vapor is crucial. We have demonstrated a 6% collection efficiency in a special wall-coated cell. We have developed a model that predicts the capture efficiency as a function of trap properties and have developed techniques for measuring the pertinent characteristics.
We report the laser cooling and trapping of neutral potassium on an open transition. Fermionic 40{}^{40}40K is captured using a magneto-optical trap (MOT) on the closed $4{S}_{1/2}\ensuremath{\rightarrow}4{P}_{3/2}$ transition at 767 nm and then transferred, with high efficiency, to a MOT on the open $4{S}_{1/2}\ensuremath{\rightarrow}5{P}_{3/2}$ transition at 405 nm. Because the 5P3/25{P}_{3/2}5P3/2​ state has a smaller linewidth than the 4P3/24{P}_{3/2}4P3/2​ state, the Doppler limit is reduced from 145 \ensuremath{\mu}K to 24 \ensuremath{\mu}K, and we observe temperatures as low as 63(6) $\ensuremath{\mu}$K. The density of trapped atoms also increases, due to reduced temperature and reduced expulsive light forces. We measure a two-body loss coefficient of $\ensuremath{\beta}=1.4(1)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$ cm3{}^{3}3/s near saturation intensity, and estimate an upper bound of $8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}18}$ cm2{}^{2}2 for the ionization cross section of the 5P5P5P state at 405 nm. The combined temperature and density improvement in the 405 nm MOT is a twenty-fold increase in phase-space density over our 767 nm MOT, showing enhanced precooling for quantum gas experiments. A qualitatively similar enhancement is observed in a 405 nm MOT of bosonic 41{}^{41}41K.
Ultracold quantum gases have become a frequently used tool for the investigation of a variety of physical issues within the last decade, ranging from general questions in quantum physics up to special topics, e.g. quantum simulations of the physical origin of high temperature superconductivity in condensed matter physics. In this thesis, experiments are presented on the creation of an ultracold quantum gas of the fermionic potassium isotope, 40K, by all-optical means. For this purpose, a new experimental setup was designed, which was started from the scratch, with the long term goal of creating a supersolid in an optical lattice. One focus of this work lies in identifying light-assisted losses as a main restriction for achieving higher 40K atom numbers in a magneto-optical trap and in identifying light-assisted losses as a main reason for a low atomic transfer efficiency from a magneto-optical trap into an optical, quasi-electrostatic dipole trap (further called optical dipole trap) for 40K atoms. Naturally, another focus of this work lies in the application of different techniques to reduce these from light-assisted losses dependent restrictions. A two-dimensional magneto-optical trap, located in the prechamber of a vacuum system, creates a continuous beam of 40K atoms. The atoms of this beam are recaptured in the main chamber of the vacuum system by a spatial dark spot magneto-optical trap. Here, a dark magneto-optical trap is implemented instead of a standard magneto-optical trap in order to reduce light-assisted losses. Up to 1x109 atoms at temperatures around 240 μK are trapped in the dark magneto-optical trap. This is a factor of ten higher compared to atom numbers of a 40K standard magneto-optical trap. The light-assisted losses in the 40K magneto-optical trap were measured as a function of the total trapping intensity and as a function of the repumping intensity. In both cases, the smallest observed loss coefficient was β ≈ 2.5x10-10 cm3/s. Compared to the smallest values of β of all other alkali elements (apart from the bosonic potassium isotopes), the light-assisted losses with 40K atoms are approximately two orders of magnitude larger. Up to 6x105 atoms were transferred from the spatial dark magneto-optical trap into the quasi-electrostatic dipole trap, which was created by using the trapping potential induced by radiation emitted by a CO2 laser operating at a wavelength near 10.6 μm. In order to reach the here reported atom numbers in the optical dipole trap, its trapping volume had to be increased in comparison to a simple dipole trap arrangement as induced with a single focused dipole trapping beam. Simultaneously, the strong confinement, as present in a tigthly focused single beam trap and as required for a subsequent evaporative cooling, had to be maintained. For this purpose, the trapping laser beam of the optical dipole trap was retroreflected in such a way that an overall optical dipole trap with a nearly doubled waist and a slightly deeper potential depth was created. By this trapping arrangement, the number of atoms confined in the optical dipole trap could be nearly doubled compared to a simple dipole trapping arrangement consisting of a single tightly focused trapping beam. The atomic transfer process itself, from the magneto-optical trap into the optical dipole trap, was organized in two steps. In a first step, the dark magneto-optical trap was transformed into a compressed magneto-optical trap by increasing the field gradient and bringing the cooling laser closer to resonance as compared to the detuning of the usual magneto-optical trap. In contrast to other experiments, the repumping laser of the magneto-optical trap was detuned to the blue of the used repumping transition. As a consequence, atoms were optically pumped into the upper hyperfine ground state |S1/2, F=7/2〉, realizing a temporal dark, compressed magneto-optical trap in analogy to the operation of a temporal dark magneto-optical trap. By this approach, light-assisted losses were reduced. In the second step of the transfer process, the light fields of the magneto-optical trap and the optical dipole trap were alternately switched on and off. In this way, a spatially inhomogeneous ac Stark shift of the cooling transitions due to the spatially inhomogeneous intensity distribution of the dipole trapping beam was avoided and again light-assisted losses were reduced during the loading phase of atoms from the compressed magneto-optical trap into the optical dipole trap. The loading rate was measured to be approximately 2.8x108 atoms/s. The light-assisted losses during loading of the optical dipole trap were determined to be β ≈ 4.8x10-10 cm3/s. In the final step of the experiment, the temperature of the atomic ensemble confined in the optical dipole trap was further reduced by evaporative cooling. After an evaporation time of about 30 s, temperatures of 140 nK were reached at typical atom numbers of 12000. The corresponding Fermi temperature is TF = 110 nK yielding a ratio T/TF ≈ 1.3 which indicates that the fermionic potassium atoms are cooled close to the onset of quantum degeneracy. In the future, an additional trapping and evaporative cooling step within a magnetic quadrupole trap should allow for an improved loading efficiency into the far detuned optical dipole trap and finally allow for a subsequent evaporative cooling to a quantum degenerate Fermi gas.