Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4
Download
1 / 25

Magnetic field effects on the CDW and SC states in ? -(BEDT-TTF) 2 KHg(SCN) 4 - PowerPoint PPT Presentation


  • 81 Views
  • Uploaded on

Magnetic field effects on the CDW and SC states in  -(BEDT-TTF) 2 KHg(SCN) 4. Dieter Andres, Sebastian Jakob , Werner Biberacher , Karl Neumaier and Mark Kartsovnik Walther-Mei ß ner-Institut , Bayerische Akademie der Wissenschaften , Garching , Germany Ilya Sheikin

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Magnetic field effects on the CDW and SC states in ? -(BEDT-TTF) 2 KHg(SCN) 4' - gram


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

Magnetic field effects on the CDW and SC states in -(BEDT-TTF)2KHg(SCN)4

Dieter Andres, Sebastian Jakob, Werner Biberacher,

Karl Neumaier and Mark Kartsovnik

Walther-Meißner-Institut, BayerischeAkademiederWissenschaften, Garching, Germany

Ilya Sheikin

Laboratoire National des Champs MagnétiquesIntenses, Grenoble, France

HaraldMüller

European Synchrotron Radiation Facility, Grenoble, France

Natalia Kushch

Institute of Problems of Chemical Physics, Chernogolovka, Russia


Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

a-(BEDT-TTF)2KHg(SCN)4: basic features

BEDT-TTF molecule:

bis(ethylenedithio)-tetrathiafulvalene

b

c

a

a

T. Mori et al., Bull. Chem. Soc. Jpn. 1990;

R. Rousseau et al., J. Phys. I (France) 1996;

P. Foury-Leylekian et al., PRB 2010

r||(300K) 10 - 20 mW•cmr/r|| ~ 104- 105ra/rc 2

r (300K) / r (1.4K) ~ 102t ||/t  670  ,coh/||  2.210-6


Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

Q

Nestinginstability

of the Fermi surface

  • CDW formation

    at8 K

verylow!!

a-(BEDT-TTF)2KHg(SCN)4: basic features

2D Fermi surface

[P. Foury-Leylekian et al., PRB 2010]

smallDCDW kBTCDWhighsensitivitytoexternalconditions:

pressure, magneticfield


Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

CDW in a magneticfield

  • Pauli paramagnetic effect: suppresses CDW [W. Dieterich & P. Fulde, 1973]

Phase diagram of a-(BEDT-TTF)2KHg(SCN)4

P. Christ, W. Biberacher, M.K., et al., JETP Lett. 2000

Q-

TCDW/TCDW(0), exp

2mBB/hvF

B

NM

CDWx

~ 23 T

CDW0

Q+

Q-< Q+

TCDW/TCDW(0)

Theory: A. Buzdin & V. Tugushev, JETP 1983

D. Zanchi et al., PRB 1996;

P. Grigoriev & D. Lyubshin, PRB 2005


Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

CDW in a magneticfield

  • Orbital effect (requires an imperfectly nested FS): stimulates CDW


Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

Real spaceorbit:

Dy ~ 1/Bz

electrons become

effectively more 1D

CDW in a magneticfield

  • Orbital effect (requires an imperfectly nested FS): stimulates CDW


Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

a-(BEDT-TTF)2KHg(SCN)4

D. Andres, M.K., et al., PRB 2001

CDW in a magneticfield

  • Orbital effect (requires an imperfectly nested FS): stimulates CDW

Theory:

D. Zanchiet al., PRB 1996


Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

a-(BEDT-TTF)2KHg(SCN)4

D. Andres, M.K., et al., PRB 2001

FICDW at t^’ > t^’ * ???

CDW in a magneticfield

  • Orbital effect (requires an imperfectly nested FS): stimulates CDW

Theory:

D. Zanchiet al., PRB 1996

L. Gor’kov& A. Lebed, J. Phys. Lett. (Paris) 1984


Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

CDW in a magneticfield

  • Field-induced CDW (FICDW) transitions

The “slow oscillations”

SdHo

  • appear at P  Pc  2.5 kbar

  • approximately periodic

  • with 1/B

P = 3 kbar

  • display a weak hysteresis

Positions of the FICDW transitions can be fitted with

t^  0.5 meV

[A. Lebed, PRL 2010]


Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

CDW in a magneticfield

  • Field-induced CDW (FICDW) transitions

FISDW

in (TMTSF)2PF6

FICDW

in a-(BEDT-TTF)2KHg(SCN)4

A. Kornilov et al., PRB 2002

FICDW is weaker than FISDW due to the paramagnetic effect!

A. Lebed, JETP Lett. 2003


Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

Superconductivity vs. CDW

R  0

R = 0

Sample #2:

zero resistance

but no Meissner!

R^ (Ohm)

  • Resistance at zero field

See also: H. Ito et al., SSC 85 1005 (1993) – inhomogeneoussuperconductivityatP = 0


Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

Superconductivity vs. CDW

  • Onset of superconductivity


Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

Superconductivity vs. CDW

  • Onset of superconductivity

CDW+SC

R  0

R = 0

The SC onset temperature is 3 times higher

in the SC/CDW coexistence region!


Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

Superconductivity in a magneticfield; P > Pc

  • Critical field ^ layers

at P = 3 kbar:x||(0)  250nm

cf. meanfreepath  1m


Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

Superconductivity in a magneticfield; P > Pc

  • Critical field // layers

1.6Hp0

Hp0: Chandrasekhar-Clogston

paramagneticlimit

GL: Hc2 (Tc-T )

dHc2/dT 12 T/K

 x^(0) = 1.0 nmd/2;

x||(0)/ x^(0)  250!


Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

Superconductivity in a magneticfield; P > Pc

Directmanifestationoftheparamagnetic pair-breaking!


Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

Summary

  • CDW state:

  • richphasediagram due totheinterplayof

  • competingPauli paramagneticandorbital

  • effectsofmagneticfield

  • SC state:

  • at P < Pc: coexistswiththe CDW state; the

  • SC onsettemperatureisdrasticallyincreased

  • in thecoexistenceregion;

  • at P >Pc:bulk SC statewith a highly

  • anisotropic Hc2nearTc(0) and a clear

  • manifestationofparamagnetic pair-breaking

  • at H // layers.


Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

Qx = 2kF + NG,

G = eayBz/

CDW in a magneticfield

  • Field-induced density wave transitions, t^’>t^’*:

-kF

kF

B


Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

CDW in a magneticfield

  • Field-induced CDW (FICDW) transitions

Commensurate splitting

(A. Bjelis et al., 1999; A. Lebed, 2003)

N =

3,4

2,3

“Spin-zero”

1,2

0,1

0

2QP = MG

2QP = (M + 1/2)G

with M - integer


Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

CDW in a magneticfield

  • Field-induced CDW (FICDW) transitions

4

4

3

3

2

N =

N =

5

3

2

2

1

1

1

0

0

0

Pauli effect on (FICDW)

no Pauli effect (FISDW)

Qx = 2kFQP + NG

Qx = 2kF + NG

G = 2eayBz/

QP = 2mBB/vF


Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

CDW in a magneticfield

  • Field-induced CDW (FICDW) transitions

4

3

3

2

N =

2

A. Lebed, JETP Lett. 78, 138 (2003)

1

1

0

0

Pauli effect on (FICDW)

no Pauli effect (FISDW)

Qx = 2kFQP + NG

Qx = 2kF + NG

G = 2eayBz/

QP = 2mBB/vF


Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

CDW in a magneticfield

  • Field-induced CDW (FICDW) transitions

Spin-zero condition:

 vF 1.2105 m/s


Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

Superconductivity vs. CDW

  • Onset of superconductivity

Low Tc

 weakfluctuations!

CDW+SC

Ginzburg-Levanyuk

parameter:

Gi(2)~ 10-5

R  0

R = 0

The SC onset temperature is 3 times higher

in the SC/CDW coexistence region!


Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

Superconductivity in a magneticfield; P > Pc

B (mT)

  • Critical field ^ layers


Magnetic field effects on the cdw and sc states in bedt ttf 2 khg scn 4

Superconductivity in a magneticfield; P > Pc

  • Critical field // layers