Organic SuperconductorsAt Extremes of High Magnetic FieldOrganic SuperconductorsAt Extremes of High Magnetic Field

C. H. MielkeLos Alamos National LaboratoryNational High Magnetic Field Laboratory

Organic SuperconductorsAt Extremes of High Magnetic Field

C. H. MielkeLos Alamos National LaboratoryNational High Magnetic Field Laboratory

NHMFL

NHMFL Magnetic Field Capabilities

• Explosively Driven– 145 T flux compression generator (~3 kg detasheet)– 800-1000 T fcg cylindrical symmetry (~20 kg HMX-9501)– 300 T Capacitor Driven exploding coils

• Controlled Waveform 90 MJ (650 MJ max)– 60T 2 second controlled waveform– 100T CW outsert CD insert 145 MJ (available 2004)

• Capacitor Driven 0.6-1.2 MJ (1.6 MJ max)– 60T “short pulse” 6ms rise 40ms decay– 50T “mid-pulse” 40ms rise 300ms decay

• DC Superconducting Magnets (to 20T)

“Fowler” Flux compressors• Max field of ~180T

• 10mm to 20mm bore

• High homogeneity

• Sample & cryostat are destroyed

• 3 kg of sheet explosive140

120

100

80

60

40

20

0100x10

-6806040200

Time (seconds)

10MT/s

5

0

-5

-10

• Explosively Driven– 145 T flux compression generator (~3 kg detasheet)– 800-1000 T fcg cylindrical symmetry (~20 kg HMX-9505)– 300 T Capacitor Driven exploding coils

• Controlled Waveform 90 MJ (650 MJ max)– 60T 2 second controlled waveform– 100T CW outsert CD insert 145 MJ (available 2004)

• Capacitor Driven 0.6-1.2 MJ (1.6 MJ max)– 60T “short pulse” 6ms rise 40ms decay– 50T “mid-pulse” 40ms rise 300ms decay

• DC Superconducting Magnets (to 20T)

NHMFL Magnetic Field Capabilities

Multi-Stage Flux Compression Generators

• Russian Design “MC1” FCG

• 800 to 1000 tesla

• 20 kg shaped explosive (PBX 9501) 95% HMX 9505 and 5% Plastic bonder

Multi Stage Flux Compression

800

600

400

200

0

Magnetic Field Intensity (tesla)

74x10-6

706866646260

Time (seconds)

First Cascade Accelerates

Second Stage Fuses

Shock Wave Hits

MC-1 Flux Compression GeneratordB/dT ~ 150 MT/sec

• Explosively Driven– 145 T flux compression generator (~3 kg detasheet)– 800-1000 T fcg cylindrical symmetry (~20 kg HMX-9505)– 300 T Capacitor Driven exploding coils

• Controlled Waveform 90 MJ (650 MJ max)– 60T 2 second controlled waveform– 100T CW outsert CD insert 145 MJ (available 2004)

• Capacitor Driven 0.6-1.2 MJ (1.6 MJ max)– 60T “short pulse” 6ms rise 40ms decay– 50T “mid-pulse” 40ms rise 300ms decay

• DC Superconducting Magnets (to 20T)

NHMFL Magnetic Field Capabilities

60

50

40

30

20

10

02.01.51.00.50.0

Time (seconds)

NHMFL 60 tesla controlled waveform magnet

100 ms flat top 200 ms flat top Stepped fiels (Specific Heat Experiments)

Specific Heat in a Kondo InsulatorJaime, et al, Nature 405 (2000) 160

60 minutes between full field shots

1.4 GW motor-generator

1m90 MJ of energy

• Explosively Driven– 145 T flux compression generator (~3 kg detasheet)– 800-1000 T fcg cylindrical symmetry (~20 kg HMX-9505)– 300 T Capacitor Driven (CD) exploding coils

• Controlled Waveform (CW) 90 MJ (650 MJ max)– 60T 2 second controlled waveform– 100T CW outsert CD insert 145 MJ (available 2004)

• Capacitor Driven 0.6-1.2 MJ (1.6 MJ max)– 60T “short pulse” 6ms rise 40ms decay– 50T “mid-pulse” 40ms rise 300ms decay

• DC Superconducting Magnets (to 20T)

NHMFL Magnetic Field Capabilities

Specifications

Outer Coil (125 MJ peak energy) (Department of Energy)

Coils 1 through 4 AL-60 Conductor 301 SS Sheet Reinforcement wound on Nitronic-40 bobbin

Coils 5 and 6 AL-15 Conductor Nitronic-40 Monolithic Reinforcement

Coil 7 Hard Cu Conductor 304 SS Monolithic Reinforcement

One Meter

Design and Materials

NHMFL’s 100 T Multi-Shot Magnet

100T peak field15mm borePulse every hour

1 msec at 100T peak field

2 secondtotal pulse duration

Insert Coil (2 MJ peak energy) (National Science Foundation) CuNb Conductor MP35N Sheet Zylon Fiber Reinforcement

10 msec above 75T

140 MJ of energy

• Explosively Driven– 145 T flux compression generator (~3 kg detasheet)– 800-1000 T fcg cylindrical symmetry (~20 kg HMX-9505)– 300 T Capacitor Driven exploding coils

• Controlled Waveform 90 MJ (650 MJ max)– 60T 2 second controlled waveform– 100T CW outsert CD insert 145 MJ (available 2004)

• Capacitor Driven 0.6-1.2 MJ (1.6 MJ max)– 60T “short pulse” 6ms rise 40ms decay– 50T “mid-pulse” 40ms rise 300ms decay

• DC Superconducting Magnets (to 20T)

NHMFL Magnetic Field Capabilities

60 tesla “short pulse”

• ~6 milli-seconds to peak field

• Work-horse of the magnet lab

• Life-time of ~500 full field shots

10 cm

30 minutes between full field shots

0.6 MJ of energy

Normal Mode of Failure

• Causes minor damage– He dewar tail– Probe insert– LN2 bucket (igloo cooler)

• Fault on lead end or sometimes in the 3rd layer midplane (due to fatigue of conductor)

• Audible report

Short Pulse Stress Failure

60 tesla magnet destroyed at 72 tesla “confinement failure”

0.8 MJ of energy

Worth the hassle for condensed matter physics

• Extreme fields quantize quasi-particle orbits

• Split Energy Bands

• Suppress Superconductivity

• Drive magnetic transitions

• Reveal new states of matter

• Ect., ect., etc….

5.0x10-8

4.5

4.0

3.5

3.0

6050403020100

Magnetic Field (tesla)

α-( - )BEDT TTF 2 ( )KHg SCN4 = 400 T mK

rf contactless conductivityƒ = 28 MHz

10-4

10-3

10-2

10-1

100

6000500040003000200010000

Frequency (tesla)

β

β−αβ+α

4α

β−α

3α2α

α

Organic Superconductors

• First Organic Superconductor Discovered in 1979

• Initial Tc of ~1K– Q1-D salt

• Various categories– “Bucky Balls”– FET types– Charge transfer salts

TetraMethylTetraSelenaFulvalene

cloride Tc=1K

-BisEthyleneDiThio-TetraThioFulvalene

Copper ThioCynate Tc=10K

-BisEthyleneDiThioTetraThioFulvalene

copper DiCyanidBromide Tc=11.6K

-BisEthelyneDiThioTetraSelenaFulvalene

Gallium TetraClorate Tc= 5K

Charge Transfer Salts begin with organic radicals

BEDT-TTF based (ET for short)

BEDT-TSF based (BETS for short)S

Se

Se

S

Se

S

S

Se

H

HHH

S

S

S

S

S

S

S

S

H

HHH

Effect of the Inorganic Anion

Organic meets Inorganic-(BEDT-TSF)2GaCl4

Half of the unit cell

The Unit Cell

-(BEDT-TSF)2GaCl4 -(BEDT-TTF)2Cu(NCS)2

a = 18 Åb = 16 Åc = 8 Å

a = 16 Åb = 8 Åc = 13 Å

Layer spacing is the important dimension

packing motif packing motif

The Fermi Surfaces

β

α

Γ

M

k

kc

b

Y

-(BEDT-TSF)2GaCl4 -(BEDT-TTF)2Cu(NCS)2

Anisotropy of the Electronic System

-(BEDT-TTF)2Cu(NCS)2-(BEDT-TTF)2Cu(NCS)2

Molecular Corridor-(BEDT-TSF)2GaCl4

4

3

2

1

06050403020100

Field (tesla)

1.0

0.8

0.6

0.4

0.2

0.0800040000

Frequency (tesla)

αƒ=670 T

βƒ=4060 T

0.10

0.05

0.00

-0.05

-0.1026 10x -324222018

1/μ0 (H T-1)

-( - )BEDT TSF2GaCl4 = 430 T mK

Magnetic Breakdown in -(BEDT-TSF)2GaCl4

Magnetic Breakdown in -(BEDT-TTF)2Cu(NCS)2

1.0

0.5

0.0

-0.5

36x10-3

34323028262422

Inverse Magnetic Field (T-1

)

T = 40 mK

T = 650 mK

Magnetic Breakdown1.0

0.8

0.6

0.4

0.2

0.01000080006000400020000

Frequency (tesla)

α = 600 T

β = 3990 Tβ − α

Pippard Magnetic Breakdownβ

α

Γ

M

k

kc

b

Y

Exponential Growth of Breakdown Amplitude

4x10-3

2

0

-2

-4

42x10-3

4038363432302826

Inverse Magnetic Field ( T-1

)

-( - )BEDT TTF 2 ( )Cu NCS4 Breakdown orbit digitally filtered = 40T mK

Forbidden Trajectories0.25

0.20

0.15

0.10

0.05

0.001000080006000400020000

Frequency (tesla)

β

β + α

β − α

β + 3αβ − 2α

-( - )BEDT TTF 2 ( )Cu NCS4

β − α α

Γ

Mk

k

Y

Anomalous Trajectories are due toStark Quantum Interference

β

α

Γ

M

k

kc

b

Y

Angular Dependent Magnetoresistance

Field Lines

PlatformSample

Rotation Axis

-(BEDT-TSF)2GaCl4

-(BEDT-TTF)2Cu(NCS)2

B = 42T (DC)

B

Belly orbits show salt to be more 3-D than

Quasi 2-D region w/B || layersPeak width is determinedby the interlayer transfer integral (t )

β

α

Γ

M

k

kc

b

Y

J. Singleton, et. al. PRL, 88 (2002).

t⊥λ ≈0.21meV

t⊥κ ≈0.04meV

C. Mielke, et. al. J. Phys. Cond. Mat., 13 (2001) 8325.

Tight-binding dispersion relation added to the effective dimer model

Using G-L theory to estimate z

302520151050

Magnetic Field (tesla)

H c2 c2H

H || planes

-( )ET 2 ( )Cu NCS4 -( )BETS 2GaCl4

Hc2⊥z =φ0

2πξxyξz

z ≈ 5Å

z ≈ 16Å

At T* ≈ 18 Å for -(BEDT-TSF)2GaCl4

10

2

3

4

5

6

7

89

100

43210

Temperature (K)

( ) ~ T (0)/(1 - )t1/2

4

5

6

7

89

10

2

3

4

5

Coherence Length (Å)

86420

Temperature (K)

-(BEDT-TTF)2Cu(NCS)2 appears to be in the 2-D limit so close to Tc we can’t resolve it

Superconducting Properties of -(BEDT-TSF)2GaCl4

and -(BEDT-TTF)2Cu(NCS)2

C. H. Mielke, J. Singleton, M-S Nam, N. Harrison, C.C. Agosta, B. Fravel, and L.K. Montgomery, J. Phys.: Condens. Matter, 13 (2001)8325.

6

5

4

3

2

1

01086420

Temperature (K)

-( )ET 2 ( )Cu NCS2

(Fit to Tc- )Tβ

β =0.73

λ-(BEDT-TSF)2GaCl4 Fit to (Tc-T)

β

β = 0.5 G-L theory 3D linear fit

Conclusions

• Creating very high magnetic fields can be exciting!

• By tuning the organic molecules the effective dimensionality of the system is readily changed

• Dimensionality is closely related to the superconducting properties

John Singleton (Oxford U. joining LANL in July)Ross McDonald (LANL Postdoctoral Fellow 3-D Fermi surfaces)Greg Boebinger, Dwight Rickel, Neil Harrison (LANL)Mike (L. K.) Montgomery (Indiana U. synthesis of organic SC) Department of Energy and the National Science Foundation