5th Institute of Physics
 
 
 
 

Dipolar quantum gases

Magnetic quantum gases and liquids of Dysprosium atoms

Abstract | Highlights | Research | The Crew | Refs & Publications | Open Positions | Bachelor- and Master-Topics

Abstract

 

In this project we experimentally investigate the dipole-dipole interactions in quantum gases like Bose-Einstein condensates (BECs).


Even though an atomic Bose-Einstein-Condensate (BEC) is a very dilute system, the most fascinating experimental results arise from the weak interactions between the particles. In most experiments the dominating interaction in a BEC is the isotropic and short-range contact interaction that can be characterized by the s-wave scattering length a. Magnitude and sign of a can be modified using Feshbach resonances. In dipolar gases a large dipole moment results in additional long range and anisotropic interactions giving rise to novel states of matter and collective phenomena. Among those are so-called super-solids and two dimensional solitons.

In 2005 we produced the first Chromium-BEC [2and we showed that it exhibits non-negligible dipolar effects [3]. Nevertheless, the dipole-dipole interactions were only a small perturbation compared to the usual contact interactions. After exploring a lossless cooling method for a thermal cloud [4], which exploits the fast dipolar relaxation [1], we focused on the strong-dipolar effects in the quantum degenerate regime. In 2007 we achieved the first quantum ferrofluid [5], i.e. a BEC with comparable contact and dipole-dipole interactions, and shortly afterwards a purely dipolar BEC [6]. Due to the anisotropic character of the dipole-dipole interactions the stability the BEC depends on the trap geometry [6] and shows an universal behavior in the large N regime. We have observed instabilities - the so-called  dipolar collapse involving an anisotropic d-wave symmetry [7]. We have then investigated the phase coherence of collapsed condensates [8]. We induced the collapse in several condensates simultaneously and let them interfere. By observing high fringe contrast, we proved that the collapsed cloud contains a remnant condensate. Also dipolar interaction in optical lattices was observed.

Since 2014 we have replaced the Chromium quantum gas by a Dysprosium BEC. Dysprosium has the highest magnetic moment of all atoms in the periodic table and due to its larger mass a reduced contact interaction. It is therefore best suited to study the dipolar phenomena. With this new system we have observed the equivalent of the Rosensweig instability which happens for classical ferrofluids, with our dipolar BEC, a quantum ferrofluid. This instability is characterized by the formation of regular patterns of peaks and valleys in the denity of the BEC. As opposed to what was previously thought, the resulting state is actually stable, characterized by the formation of droplets [30]. These droplets are actually made of a novel quantum liquid, where the attraction due to the dipolar interaction, which tends to drive a collapse, is balanced by quantum fluctuations of the BEC field as dictated by Heisenberg uncertainty principle [31]. 

A quantum ferrofluid: The contact interaction, symbolized by the grey “hard sphere” on the schematic representation of the atoms (top), is reduced from top to bottom, while the magnetic dipole moment of the atoms (green and red arrow) stays constant. One thus enhances the effects of the dipolar interactions between the magnetic moments of the atoms. This manifests itself in an elongation of the condensate along the magnetization direction, yielding a clear change in the condensate ellipticity (false colour experimental images at the bottom).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Illustration of the behaviour of a quantum ferrofluid: When the quantum ferrofluid is placed in a flat "pancake" trap (a, left), decreasing the contact interaction such that the gas becomes dominated by the dipolar interaction results in the formation of stable density waves and eventually of droplets (a, right and b). This is the equivalent of the rosensweig instability of classical ferrofluid.

 

 

 

 

 

 

 

 

 

Abstract | Highlights | Research | The Crew | Refs & Publications | Open Positions | Bachelor- and Master-Topics

Highlights

18.07.2018Superfluidity becomes directional more...
19.04.2018Single-blade quantum scissors more...
27.11.2017Striped states with tilted dipoles more...
10.11.2016Self-bound droplets of a quantum liquid more...
23.05.2016Making a quantum liquid from a quantum gas more...
01.02.2016New state of matter: Quantum gas, liquid and crystal all-in-one more...
 14.10.2015Emergence of chaotic scattering in ultracold Er and Dy more...
 29.04.2014Narrow-line magneto-optical trap for dysprosium atoms more...
 16.01.2013Spectroscopy of a narrow-line optical pumping transition in dysprosium more...
 09.11.2012Deconfinement-induced collapse of a coherent array of dipolar Bose-Einstein condensates more...
 19.03.2009Artist Brigitte Simon inspired by Chrom Bose Nova more...
 18.02.2009Coherent collapse of a dipolar BEC in different trapping potentials ... more...
19.06.2008On the cover of PRL: d-wave collapse and explosion of a dipolar BEC more...
 13.05.2008Akademiepreis für Stuttgarter Physiker more...
 27.02.2008Stabilization of a purely dipolar quantum gas against collapse more...
 27.07.2007A quantum ferrofluid - creation of the first quantum gas with strong dipolar interactions, by using a Feshbach resonance in a Chromium BEC. more...
 15.11.2006Demagnetization cooling of a gas more...
 10.11.2005Observation of dipole-dipole interaction in a degenerate quantum gas more...
 03.03.2005Here we update our previous report on Bose-Einstein condensation in a gas of chromium more...
 26.11.2004Bose-Einstein Condensation of Chromium atoms more...
 26.07.2004Feshbach resonances in 52Cr collisions more...
 14.07.2004Piet Schmidt wins prize for the best PhD thesis more...
 15.10.2003Dipolar Relaxation in a magnetically trapped gas of Chromium atoms more...
 17.04.2003Measurement of the scattering lengths of 52Cr and 50Cr more...
 10.12.2002A combined trap for chromium and rubidium atoms more...
 24.04.2002Theory on tunable dipolar interaction in quantum gases more...
 14.11.2001First Ioffe-Pritchard trap for chromium atoms more...

Abstract | Highlights | Research | The Crew | Refs & Publications | Open Positions | Bachelor- and Master-Topics

Research

Figure 1: Stability of different trap geometries: In an pancake-shaped trap (A) the dipoles mainly repel each other, whereas in a cigar-shaped trap (B) the interaction is predominantly attractive. We find good agreement between experiment and a simple model (C). For details see [6].


 

Figure 2: Interfering Chromium-BECs.

 

Chromium 2008 (pdf presentation)

Chromium BEC tutorial (pdf)

 

Abstract | Highlights | Research | The Crew | Refs & Publications | Open Positions | Bachelor- and Master-Topics

The Crew

Viraatt Anasuri(Master Student)
Arup Bhowmick(Post Doc)
Fabian Böttcher(Doktorand)
Mingyang Guo(Post Doc)
Jens Hertkorn(Master Student)
Jan-Niklas Schmidt(Doktorand)
Matthias Wenzel(Doktorand)

Abstract | Highlights | Research | The Crew | Refs & Publications | Open Positions | Bachelor- and Master-Topics

Refs & Publications

[1]S. Hensler, J. Werner, A. Griesmaier, P.O. Schmidt, A. Görlitz, T. Pfau, S. Giovanazzi and K. Rzazewski
"Dipolar Relaxation in an ultra-cold Gas of magnetically trapped chromium atoms"
Appl. Phys. B 77, 765 (2003)
[2]A. Griesmaier, J. Werner, S. Hensler, J. Stuhler, and T. Pfau
"Bose-Einstein condensation of chromium"
Phys. Rev. Lett. 94, 160401 (2005)
[3]S. Hensler, A. Greiner, J. Stuhler, and T. Pfau
"Depolarisation cooling of an atomic cloud"
Europhys. Lett. 71, 918 (2005)
[4]J. Stuhler, A. Griesmaier, T. Koch, M. Fattori, S. Giovanazzi, P. Pedri, L. Santos, and T. Pfau
"Observation of Dipole-Dipole Interaction in a Degenerate Quantum Gas"
Phys. Rev. Lett. 95, 150406 (2005)
[5]L. Santos and T. Pfau
"Spin-3 Chromium Bose-Einstein Condensates"
Phys. Rev. Lett. 96, 190404 (2006)
[6]A. Griesmaier, J. Stuhler, and T. Pfau
"Production of a chromium Bose-Einstein condensate"
Appl. Phys. B 82, 211 (2006)
[7]M. Fattori, T. Koch, S. Goetz, A. Griesmaier, S. Hensler, J. Stuhler, and T. Pfau
"Demagnetization cooling of a gas"
Nature Physics 2, 765 (2006)
[8]J. Stuhler, A. Griesmaier, J. Werner, T. Koch, M. Fattori, and T. Pfau
"Ultracold chromium atoms: From Feshbach resonances to a dipolar Bose-Einstein condensate"
J. Mod Opt. 54, 647 (2007)
[9]B. Fröhlich, T. Lahaye, B. Kaltenhäuser, H. Kübler, S. Müller, T. Koch, M. Fattori, and T. Pfau
"A two-frequency acousto-optic modulator driver to improve the beam pointing stability during intensity ramps"
Rev. Sci. Instrum. 78, 043101 (2007); ; arXiv: physics/0701183 (2007)
[10]K. Glaum, A. Pelster, H. Kleinert, and T. Pfau
"Critical Temperature of Weakly Interacting Dipolar Condensates"
Phys. Rev. Lett. 98, 080407 (2007)
[11]S. Giovanazzi, L. Santos, and T. Pfau
"Collective oscillations of dipolar Bose-Einstein condensates and accurate comparison between contact and dipolar interaction"
Phys. Rev. A 75, 015604 (2007); ; arXiv:cond-mat/0608291 (2007)
[12]Th. Lahaye, T. Koch, B. Fröhlich, M. Fattori, J. Metz, A. Griesmaier, S. Giovanazzi, and T. Pfau
"Strong dipolar effects in a quantum ferrofluid"
Nature 448, 672 (2007)
[13]L. Santos, M. Fattori, J. Stuhler, and T. Pfau
"Spinor condensates with a laser-induced quadratic Zeeman effect"
Phys. Rev. A 75, 053606 (2007); ; arXiv: cond-mat/0612191, (2007)
[14]T. Koch, T. Lahaye, J. Metz, B. Fröhlich, A. Griesmaier, and T. Pfau
"Stabilizing a purely dipolar quantum gas against collapse"
Nature Physics 4, 218 (2008)
[15]A. Muramatsu and T. Pfau (eds.)
"Focus on Quantum Correlations in Tailored Matter"
New J. Phys. 10, 045001 (2008)
[16]T. Lahaye, J. Metz, B. Fröhlich, T. Koch, M. Meister, A. Griesmaier, T. Pfau, H. Saito, Y. Kawaguchi, and M. Ueda
"d-Wave Collapse and Explosion of a Dipolar Bose-Einstein Condensate"
Phys. Rev. Lett 101, 080401 (2008)
[17]J. Metz, T. Lahaye, B. Fröhlich, A. Griesmaier, T. Pfau, H. Saito, Y. Kawaguchi, and M. Ueda
"Coherent collapse of a dipolar Bose-Einstein condensate for different trap geometries"
New J. Phys. 11, 055032 (2009); arXiv:0901.1300v1 [physics.atom-ph]
[18]S. Müller, J. Billy, E. A. L. Henn, H. Kadau, A. Griesmaier, M. Jona-Lasinio, and L. Santos
"Stability of a dipolar Bose-Einstein condensate in a one-dimensional lattice"
Phys. Rev. A 84, 053601 (2011); doi: 10.1103/PhysRevA.84.053601
[19]A. Maluckov, G. Gligoric, L. Hadzievski, B. A. Malomed, and T. Pfau
"Stable periodic density waves in dipolar Bose-Einstein condensates trapped in optical lattices"
Phys. Rev. Lett. 108, 140402 (2012)
[20]D. Peter, K. Pawłowski, T. Pfau, and K. Rzążewski
"Mean-field description of dipolar bosons in triple-well potentials"
J. Phys. B: At. Mol. Opt. Phys. 45, 225302 (2012); doi: 10.1088/0953-4075/45/22/225302
[21]J. Billy, E. A. L. Henn, S. Müller, T. Maier, H. Kadau, A. Griesmaier, M. Jona-Lasinio, L. Santos, and T. Pfau
"Deconfinement-induced collapse of a coherent array of dipolar Bose-Einstein condensates"
Phys. Rev. A 86, 051603(R) (2012); doi: 10.1103/PhysRevA.86.051603
[22]D. Peter, A. Griesmaier, T. Pfau, and H. P. Büchler
"Driving dipolar fermions into the quantum Hall regime by spin-flip induced insertion of angular momentum"
Phys. Rev. Lett. 110, 145303 (2013); arXiv:1302.1308 [cond-mat.quant-gas]; (editor
[23]A. Maluckov, G. Gligoric, L. Hadzievski, B. A. Malomed, and T. Pfau
"High- and low-frequency phonon modes in dipolar quantum gases trapped in deep lattices"
Phys. Rev. A 87, 023623 (2013); arXiv:1302.2410
[24]M. Schmitt, E. A. L. Henn, J. Billy, H. Kadau, T. Maier, A. Griesmaier, and T. Pfau
"Spectroscopy of a narrow-line optical pumping transition in dysprosium"
Opt. Lett. 38, 637 (2013); doi: 10.1364/OL.38.000637
[25]K. Pawlowski, P. Bienias, T. Pfau and K. Rzazewski
"Correlations of a quasi-two-dimensional dipolar ultracold gas at finite temperatures"
Phys. Rev. A 87, 043620; doi: 10.1103/PhysRevA.87.043620
[26]P. Bienias, K. Pawlowski, T. Pfau and K. Rzazewski
"Ground state of a two component dipolar Fermi gas in a harmonic potential"
Phys. Rev. A 88, 043604 (2013); arXiv:1308.0567; doi: 10.1103/PhysRevA.88.043604
[27]J. B. Balewski, A. T. Krupp, A. Gaj, D. Peter, H. P. Büchler, R. Löw, S. Hofferberth, and T. Pfau
"Coupling a single electron to a Bose–Einstein condensate"
Nature 502, 664 (2013); doi: 10.1038/nature12592
[28]T. Maier, H. Kadau, M. Schmitt, A. Griesmaier, and T. Pfau
"Narrow-line magneto-optical trap for dysprosium atoms"
Optics Letters 39 , 3138(2014); arXiv:1403.1499
[29]T. Karpiuk, M. Brewczyk, K. Rzążewski, A. Gaj, J. B. Balewski, A. T. Krupp, M. Schlagmüller, R. Löw, S. Hofferberth, and T. Pfau
"Imaging single Rydberg electrons in a Bose–Einstein condensate"
New Journal of Physics 17, 053046 (2015); doi: 10.1088/1367-2630/17/5/053046
[30]T. Maier, I. Ferrier-Barbut, H. Kadau, M. Schmitt, M. Wenzel, C. Wink, T. Pfau, K. Jachymski, P. S. Julienne
"Broad Feshbach resonances in collisions of ultracold Dysprosium atoms"
Phys. Rev. A 92, 060702(R) (2015); arXiv:1506.01875
[31]T. Maier, H. Kadau, M. Schmitt, M. Wenzel, I. Ferrier-Barbut, T. Pfau, A. Frisch, S. Baier, K. Aikawa, L. Chomaz, M. J. Mark, F. Ferlaino, C. Makrides, E. Tiesinga, A. Petrov, S. Kotochigova
"Emergence of chaotic scattering in ultracold Er and Dy"
Phys. Rev. X 5, 041029 (2015)
[32]H. Kadau, M. Schmitt, M. Wenzel, C. Wink, T. Maier, I. Ferrier-Barbut, T. Pfau
"Observing the Rosensweig instability of a quantum ferrofluid"
Nature 530, 194 (2016), arXiv:1508.05007; doi: 10.1038/nature16485
[33]I. Ferrier-Barbut, H. Kadau, M. Schmitt, M. Wenzel, T. Pfau
"Observation of quantum droplets in a strongly dipolar Bose gas"
Phys. Rev. Lett. 116, 215301 (2016); doi: 10.1103/PhysRevLett.116.215301
[34]I. Ferrier-Barbut, M. Schmitt, M. Wenzel, H. Kadau and T. Pfau
"Liquid quantum droplets of ultracold magnetic atoms"
J. Phys. B: At. Mol. Opt. Phys 49, 214004 (2016), arXiv:1607.07355; doi: 10.1088/0953-4075/49/21/214004
[35]M. Schmitt, M. Wenzel, B. Böttcher, I. Ferrier-Barbut, T. Pfau
"Self-bound droplets of a dilute magnetic quantum liquid"
Nature 539, 259 (2016), arXiv:1607.07355; doi: 10.1038/nature20126
[36]Igor Ferrier-Barbut
"Smashing magnets"
New Journal of Physics 18, 111004 (2016); doi: 10.1088/1367-2630/18/11/111004
[37]M. Wenzel, F. Böttcher, T. Langen, I. Ferrier-Barbut, T. Pfau
"Striped states in a many-body system of tilted dipoles"
Phys. Rev. A 96 053630 (2017); doi: 10.1103/PhysRevA.96.053630
[38]Igor Ferrier-Barbut and Tilman Pfau
"Quantum liquids get thin"
Science 359,274 (2018); doi: 10.1126/science.aar3785
[39]Igor Ferrier-Barbut, Matthias Wenzel, Fabian Böttcher, Tim Langen, Tilman Pfau
"Onset of a modulational instability in trapped dipolar Bose-Einstein condensates"
Phys. Rev. A 97 011604 (2018); doi: 10.1103/PhysRevA.97.011604
[40]Igor Ferrier-Barbut, Matthias Wenzel, Fabian Böttcher, Tim Langen, Mathieu Isoard, Sandro Stringari, and Tilman Pfau
"Scissors Mode of Dipolar Quantum Droplets of Dysprosium Atoms"
Phys. Rev. Lett. 120, 160402 (2018); doi: 10.1103/PhysRevLett.120.160402

Abstract | Highlights | Research | The Crew | Refs & Publications | Open Positions | Bachelor- and Master-Topics

Open Positions

We are planning a new setup for a degenerate Dysprosium gases and are looking forquantum ferrofluid

  • a PhD student

If you are interested in working on exotic states of matter and like to setup new things, contact mailto icon Tilman Pfau via email/phone or just come by and visit our labs.

Interested? Here you find the recent papers on our quantum liquid

M. Schmitt, M. Wenzel, B. Böttcher, I. Ferrier-Barbut, T. Pfau
Self-bound droplets of a dilute magnetic quantum liquid
Nature 539, 259 (2016), arXiv:1607.07355

I. Ferrier-Barbut, H. Kadau, M. Schmitt, M. Wenzel, T. Pfau
"Observation of quantum droplets in a strongly dipolar Bose gas"
Phys. Rev. Lett. 116, 215301 (2016)

Abstract | Highlights | Research | The Crew | Refs & Publications | Open Positions | Bachelor- and Master-Topics

Bachelor- and Master-Topics

Simulations of beyond-mean-field dipolar Bose-Eintein condensates (Master thesis)

 

The current state-of-the-art theoretical model to describe strongly dipolar Bose-Eintein condensates of Dysprosium is the so-called extended Gross-Pitaevskii equation. This equation is based on the mean-field Gross-Pitaevskii equation including the long-range anisotropic dipole-dipole interaction, to which an effective term is added to take into account the effect of beyond-mean-field corrections. These correction arise from quantum fluctuations in the fluid and act as an effective extra non-linearity. The goal of this project is to perform simulations of this equation to compare to experiments in order to test the thepry at the current level and make useful predictions for our experiments on Dysprosium. These numerical simultions are developped in our group, and they allow to implement the exact experimental conditions.

Contact:

 T.Pfau

 

Abstract | Highlights | Research | The Crew | Refs & Publications | Open Positions | Bachelor- and Master-Topics