Dirac Strings and Magnetic Monopoles in Spin Ice Dy2Ti2O7

While sources of magnetic fields - magnetic monopoles - have so far proven elusive as elementary particles, several scenarios have been proposed recently in condensed matter physics of emergent quasiparticles resembling monopoles. A particularly simple proposition pertains to spin ice on the highly frustrated pyrochlore lattice. The spin ice state is argued to be well-described by networks of aligned dipoles resembling solenoidal tubes - classical, and observable, versions of a Dirac string. Where these tubes end, the resulting defect looks like a magnetic monopole. We demonstrate, by diffuse neutron scattering, the presence of such strings in the spin-ice Dy2Ti2O7. This is achieved by applying a symmetry-breaking magnetic field with which we can manipulate density and orientation of the strings. In turn, heat capacity is described by a gas of magnetic monopoles interacting via a magnetic Coulomb interaction.

Note:

32 pages (19 pages of article, 13 pages of supporting online material)

ice: spin
string: Dirac
magnetic monopole: interaction
interaction: Coulomb
n: scattering
lattice
detector: network
symmetry breaking
quasiparticle
defect

References(21)

Figures(0)

[1]

MAGNETIC MONOPOLES

John Preskill
(
- Caltech
)

- Ann.Rev.Nucl.Part.Sci. 34 (1984) 461-530
•
DOI:
- 10.1146/annurev.ns.34.120184.002333

[2]

New limits on magnetic monopoles searches from accelerator and non-accelerator experiments

Michela Cozzi
(
- Bologna U. and
- INFN, Bologna
)

- Phys.Atom.Nucl. 70 (2007) 118-122
•
e-Print:
- hep-ex/0703014
•
DOI:
- 10.1134/S1063778807010127

[3]

S.T. Bramwell
,
M.J.P. Gingras

- Science 294 1495

[4]

L. Pauling

- J.Am.Chem.Soc. 57 2680

[5]

A.P. Ramirez
,
A. Hayashi
,
R.J. Cava
,
R. Siddharthen
,
B.S. Shastry

- Nature 399 333

[6]

S.V. Isakov
,
K. Gregor
,
R. Moessner
,
S.L. Sondhi

- Phys.Rev.Lett. 93 167204

[7]

T. Yavorâskii
,
T. Fennell
,
M.J.P. Gringras
,
S.T. Bramwell

- Phys.Rev.Lett. 101 037204

[8]

T. Fennell
,
S.T. Bramwell
,
D. McMorrow
,
P. Manuel
,
A. Wildes

- Nature Phys. 3 566

[9]

Phys.Rev. B. : 72 (2005) 224411

T. Fennell
,
O.A. Petrenko
,
B. FÃ¥k
,
J.S Gardner
,
S.T. Bramwell

et al.

[10]

Phys.Rev. B. : 70 (2004) 134408

T. Fennell
,
O.A. Petrenko
,
B. FÃ¥k
,
S.T. Bramwell
,
M. Erjalran

et al.

[11]

C. Castelnovo
,
R. Moessner
,
S.L. Sondhi

- Nature 451 42

[12]

Electrostatic correlations: From plasma to biology

Yan Levin
(
- Rio Grande do Sul U.
)

- Rept.Prog.Phys. 65 (2002) 1577
•
e-Print:
- cond-mat/0207086
•
DOI:
- 10.1088/0034-4885/65/11/201

[13]

Signature of magnetic monopole and Dirac string dynamics in spin ice

- Nature Phys. 5 (2009) 258-261
•
e-Print:
- 0903.1074
•
DOI:
- 10.1038/nphys1227

[14]

Quantised singularities in the electromagnetic field,

Paul Adrien Maurice Dirac
(
- St John's Coll., Cambridge
)

- Proc.Roy.Soc.Lond.A 133 (1931) 821, 60-72
•
DOI:
- 10.1098/rspa.1931.0130

[15]

B. Canals
,
D.A. Garanin

- Can.J.Phys. 79 1323

[16]

at al

S.T. Bramwell

- Phys.Rev.Lett. 87 047205

[17]

L.D.C. Jaubert
,
J.C. Chalker
,
P.W.C. Holdsworth
,
R. Moessner

- Phys.Rev.Lett. 100 067207

[18]

L.D.C. Jaubert
,
J.C. Chalker
,
P.C.W. Holdsworth
,
R. Moessner

- J.Phys.Conf.Ser. 145 012024

[19]

J. Snyder
,
J.S. Slusky
,
R.J. Cava
,
P. Schiffer

- Nature 413 48

[20]

We wish to thank Shivaji Sondhi for help and encouragement, John Chalker for insights into the expected behaviour in field of the correlation functions, and Konrad Siemensmeyer with his help with sample cutting and preparation. Jochen Heinrich helped with COMSOL Multiphysics used for the demagnetisation calculations. S.A.G. would like to acknowledge financial support from the Royal Society (UK);

[20]

was supported by EPSRC under Grant No. GR/R83712/01

C.Ca