Negative Oxygen Isotope Effect on the Static Spin
Stripe Order in La1.875Ba0.125CuO4
Zurab Guguchia
Physik-Institut der Universität Zürich, Switzerland
Laboratory for Muon Spin Spectroscopy, Paul-Scherrer Institut, Switzerland
Thank you!
Tbilisi State University
Alexander Shengelaya
Markus Bendele
Hugo Keller
Laboratory for Muon Spin Spectroscopy (PSI)
Rustem Khasanov
Laboratory for Developments and Methods (PSI)
Ekaterina Pomjakushina
Kazimierz Conder
Outline
• Introduction
 Stripe phase in cuprates.
 Isotope effects.
 Muon Spin Rotation (µSR) technique.
• Results
 Oxygen Isotope Effect (OIE) on superconductivity in LBCO-1/8.
 OIE on the static spin stripe order in LBCO-1/8.
 Pressure effects in LBCO-1/8.
• Conclusions
Superconductivity in La2-xBaxCuO4
Moodenbaugh et al, Phys. Rev. B 38, 4596 (1988).
Axe et al, Phys. Rev. Lett. 62, 2751 (1989).
Hücker et al, Phys. Rev. B 83, 104506 (2011).
Experimental evidence for static stripes in La1.48Nd0.4Sr0.12CuO4
Neutron Scattering
Spin order
Real space
Charge order
Tranquada et al, Nature (London) 375, 561 (1995).
Guguchia, PhD thesis,University of Zürich (2013).
M. Vojta, Adv. Phys. 58, 699 (2009) and references therein.
T. Wu et. al., Nature 477, 191 (2011).
Central issues in Cuprates
 What is microscopic origin of the stripe formation?
The stripe phase may be caused by electronic and/or electron-lattice
interaction.
Do they contain all ingredients required for stripe formation?
 Do stripes promote or inhibit superconductivity?
Zaanen and Gunnarson Phys. Rev. B 40, 7391 (1989).
White and Scalapino, PRL 80, 1272 (1998).
Emery and Kivelson, Physica C 209, 597 (1993).
M. Vojta, Adv. Phys. 58, 699 (2009).
Conventional superconductivity
Electron-phonon interaction
Isotope effect:
Tc  M  ,
  -d ln Tc / d ln M .
Ranges from 0.2-0.5 in elemental metals
Weak coupling BCS predicts a value of  = 0.5
C.A. Reynolds et. al., Phys. Rev. 78, 487 (1950).
E. Maxwell, Phys. Rev. 78, 477 (1950).
J. Bardeen et. al., Phys. Rev. 108, 1175 (1957).
Unconventional Oxygen Isotope effects (OIE’s) in cuprates
J. Hofer et. al., PRL 84, 4192 (2000).
K.A. Müller, J. Phys. Condens. Matter 19, 251002 (2007).
H. Keller et. al., Materials today 11, 9 (2008).
Shengelaya et. al, PRL 83, 24 (1999).
Khasanov et. al., PRL 101, 077001
(2008).
Lanzara et. al., J. Phys. Condens.
Matter 11, L541 (1999).
Rubio Temprano et. al., PRL 84, 1990
(2000).
Zhech et. al., Nature 371, 681–683,
1994.
Isotope effect on Tc near 1/8
M.K. Crawford et. al., Science 250, 1390 (1990).
J.P. Franck et. al., PRL 71, 283 (1993).
B. Batlogg et. al., PRL 59, 912 (1987).
G.M. Zhao et. al., J. Phys.: Condens. Matter 10, 9055 (1998).
J. Hofer et. al., PRL 84, 4192 (2000).
G.Y. Wang et. al., PRB 75, 212503 (2007).
Muon-spin rotation (μSR) technique
TRIUMF http://neutron.magnet.fsu.edu/muon_relax.html
μSR in magnetic materials
1.0
Muon Spin Polarisation
0.8
homogeneous
0.6
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
-1.0
0
1
2
3
4
5
6
7
8
9
10
7
8
9
10
Time ((s)
s)
time
Muon Spin Polarisation
1.0
inhomogeneous
0.8
0.6
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
-1.0
0
1
2
3
4
5
6
Time (s)
time
(s)
Courtesy of H. Luetkens
amplitude
frequency
Damping
→ magnetic volume fraction
→ average local magnetic field
→ magnetic field distribution / magnetic fluctuations
Magnetization experiments
Z. Guguchia et al., Phys. Rev. Lett. (2014).
Z. Guguchia et al., New Journal of Physics 15, 093005 (2013).
Tranquada et. al., PRB 78, 174529 (2008).
Li et. al., PRL 99, 067001 (2007).
Isotope effect on Tc in La1.875Ba0.125CuO4
Tc  M  .
  -d ln Tc / d ln M .
Z. Guguchia et al., Phys. Rev. Lett. (2014).
Tc1  29.7(1)K and
16
Tc1  28.3(1) K.
18
Oxygen Isotope effect on Tso


1
A(T ) / A(0)  a 1 
 b
exp[(
T

T
)
/

T
]

1
so
so


Z. Guguchia et al., Phys. Rev. Lett. (2014).
Oxygen Isotope effect on Tso


1
A(T ) / A(0)  a 1 
 b
exp[(
T

T
)
/

T
]

1
so
so


Z. Guguchia et al., Phys. Rev. Lett. (2014).
Tso  32.9(3)K and
16
Tso  34.8(2) K.
18
Oxygen Isotope effect on Tso


1
A(T ) / A(0)  a 1 
 b
exp[(
T

T
)
/

T
]

1
so
so


Z. Guguchia et al., Phys. Rev. Lett. (2014).
Tso  32.9(3)K and
16
Tso  34.8(2) K.
18
G.M. Luke et. al., Physica C 185-9, 1175 (1991).
B. Nachumi et. al., PRB 58, 8760 (1998).
OIE effect on Tso and magnetic fraction Vm
Z. Guguchia et al., Phys. Rev. Lett. (2014).
Summary of the OIE studies on La1.875Ba0.125CuO4
T
 0.57 (6), Vm  0.71(9).
SO
Give evidence for stripe-lattice coupling in cuprates.
T
SO
 0.57 (6),  Tc1  0.46(6).
Superconductivity and stripe order are competing phenomena.
Pressure experiments with SQUID and µSR
SQUID (Maisuradze and Guguchia)
Z. Guguchia et al., New Journal of Physics 15, 093005 (2013).
µSR
(R. Khasanov)
Pressure effect on static spin-stripe order in La1.875Ba0.125CuO4
Vsc(0) + Vm(0) ≈ 1
Z. Guguchia et al., New Journal of Physics 15, 093005 (2013).
LTT structural phase under pressure
Hücker et al, PRL 104, 057004 (2010).
Pressure effect on the isotope effect inLBCO-1/8
Conclusions
 Large negative OIE’s were observed on Tso and Vm in La2-xBaxCuO4
(x = 1/8).
 Oxygen-isotope shifts of Tc and TSO are sign reversed. Stripe order
and superconductivity are competing orders.
 The electron-lattice interaction is involved in the stripe formation and
is a crucial factor controlling the competition between the stripe
order and superconductivity.
 A purely electronic mechanism can not explain the present isotope
and pressure experiments!
Thank you very much
for your attention!