Interfacing ultracold atoms with
A. D. West1, K. J. Weatherill1, T. Hayward2, D. Allwood2 and I. G. Hughes1
1Joint Quantum Centre (JQC) Durham – Newcastle, Department of Physics,
Durham University, Durham, DH1 3LE, UK
2Department of Engineering Materials, University of Sheffield, Sheffield, UK
We present a first demonstration of interaction of ultracold atoms with domain walls within magnetic nanowires. Planar permalloy
nanowires host oppositely orientated domains, divided by domain walls. Fringing fields are produced at the walls . An array of
serpentine nanowires gives a 2D array of domain walls, mimicing the sinusoidal magnetisation pattern required for an ideal magnetic
mirror . The domain wall structure is reconfigurable by external magnetic fields . A cloud of ~107 87Rb atoms at 10 mK, optically
pumped into the weak field seeking F=2, mF = 2 state is reflected by these fields. Monte Carlo simulations accurately predict the
signal observed from an interrogating light sheet. Using the bounce signal we infer characteristics of the nanowire array. Future work
aims to probe van der Waals potentials at short distances. We also present planned work to use the field from a single domain wall to
create a tight (~1 MHz) atom trap. Once in such a trap, atoms can be transported above nanowires by application of a small magnetic
field, inducing domain wall motion. Such a setup bears all the hallmarks
of a scheme
quantum information processing.
Made from Permalloy (Ni81Fe19)
• Very soft ferromagnetic material
• Lithographically fabricated using
e-beam and lift off processing.
Host head-to-head or tail-to-tail
reversal (left) yields out of
plane magnetic fields (bottom
determines the domain
An atom’s intrinsic magnetic moment,
, interacts with field produced by
mFgF > 0 gives weak-field-seeking
state; atoms entering fringing fields
Ideal mirror has sinusoidal magnetisation, giving an evanescent field
proportional to the period of the pattern.
A domain wall based mirror represents a quantum
combining ultracold physics and spintronic technology.
Can image the
fields using MOKE or
scanning Hall probe
Mobile Atom Trap:
Field gradients up to
The field from a single domain
can be approximated by :
Choose a serpentine pattern of nanowires which produces a 2D
array of domain walls.
External fields toggle ‘on’ (lower) and ‘off’ (upper) states.
trapping potential (left):
Resulting periodic field mimics an ideal magnetic mirror (above
the interaction as a point one,
w giving an
effective surface (below right).
The massive field gradients then give
a very high trap frequency.
The presence of a magnetic zero leads to rapid Majorana losses.
Many conventional techniques are not applicable for nanoscale
traps – we propose a new method of creating a time-averaged
potential, using piezoelectric actuation :
the field source produces
a harmonic potential.
We have observed the diffuse reflection of a cloud of ultracold
atoms, shown in fluorescence images below :
The trap is also deeper
and more adiabatic than
We anticipate wTrap ~MHz
and depths of around 200
R = 0.25
R = 0.75
R = 1.00
We also use a weak light sheet to
Results (left) are seen to agree
well with Monte Carlo simulations.
By increasing the amplitude of movement (R) the trap topology
changes to being toroidal (above and below left).
Colder atoms give a larger, better
By reconfiguring the mirror
Traps based on domain walls are inherently mobile – they can be
moved by currents or external fields.
Networks of such traps present an ideal architecture for quantum
The atoms then act as a
probe of the micromagnetic
The closest approach is very
calculating magnetic nanowire domain wall fringing
der Waals region.
 A. D. West, T. J. Hayward, K. J. Weatherill, T. Schrefl, D. A. Allwood and I. G. Hughes, A simple model for
fields, J. Phys. D. 45, 095002 (2012).
 E. A. Hinds and I. G. Hughes, Magnetic atom optics: mirrors, guides, traps and chips for atoms, J. Phys. D, 32 R119 (1999).
 T. J. Hayward, A. D. West, K. J. Weatherill, P. J. Curran, P. W. Fry, P. M. Fundi, M. R. J. Gibbs, T. Schrefl, C. S. Adams, I. G. Hughes, S. J. Bending and D.
A. Allwood, Design and characterization of a field-switchable nanomagnetic atom mirror, J. Appl. Phys. 108, 043906 (2010)
 D. A. Allwood, T. Schrefl, G. Hrkac, I. G. Hughes and C. S. Adams, Mobile atom traps using magnetic nanowires, Appl. Phys. Lett. 89, 014102 (2006).
 J. Fortágh and C. Zimmerman, Magnetic microtraps for ultracold atoms, Rev. Mod. Phys. 79 235 (2005) and references therein.
 R. Folman, P. Krüger, J. Schmiedmayer, J. Denschlag and C. Henkel, Microscopic atom optics: from wires to an atom chip, Adv. Atom. Mol. Opt. Phys. 48 263
(2002) and references therein.
 A. D. West, K. J. Weatherill, T. J. Hayward, P. W. Fry, T. Schrefl, M. R. J. Gibbs, C. S. Adams, D. A. Allwood and I. G. Hughes, Realization of the
manipulation of ultracold atoms with a reconfigurable nanomagnetic system of domain walls, Nano Letters DOI: 10.1021/nl301491m.
 A. D. West, C. G. Wade, K. J. Weatherill and I. G. Hughes, Piezoelectrically-actuated time-averaged atomic microtraps, Appl. Phys. Lett., 3 023115 (2012).
This work was carried out in
collaboration with colleagues
at the University of Sheffield.
This project is funded by
EPSRC grants EP/F025459/1