Organic Superconductors At Extremes of High Magnetic Field Organic Superconductors At Extremes of High Magnetic Field C. H. Mielke Los Alamos National Laboratory National High Magnetic Field Laboratory

Organic Superconductors At Extremes of High Magnetic Field C. H. Mielke Los Alamos National Laboratory National High Magnetic Field Laboratory NHMFL

NHMFL Magnetic Field Capabilities Explosively Driven –145 T flux compression generator (~3 kg detasheet) – 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 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 explosive

Explosively Driven –145 T flux compression generator (~3 kg detasheet) – 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 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

Explosively Driven –145 T flux compression generator (~3 kg detasheet) – 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 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

Specific Heat in a Kondo Insulator Jaime, et al, Nature 405 (2000) minutes between full field shots 1.4 GW motor-generator 1m 90 MJ of energy

Explosively Driven –145 T flux compression generator (~3 kg detasheet) – 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 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 field 15mm bore Pulse every hour 1 msec at 100T peak field 2 second total 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) – 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 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 –LN 2 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….

Organic Superconductors First Organic Superconductor Discovered in 1979 Initial T c of ~1K –Q1-D salt Various categories –“Bucky Balls” –FET types –Charge transfer salts TetraMethylTetraSelenaFulvalene cloride T c =1K  -BisEthyleneDiThio-TetraThioFulvalene Copper ThioCynate T c =10K  -BisEthyleneDiThioTetraThioFulvalene copper DiCyanidBromide T c =11.6K -BisEthelyneDiThioTetraSelenaFulvalene Gallium TetraClorate T c = 5K

Charge Transfer Salts begin with organic radicals BEDT-TTF based (ET for short) BEDT-TSF based (BETS for short)

Effect of the Inorganic Anion

Organic meets Inorganic -(BEDT-TSF) 2 GaCl 4 Half of the unit cell

The Unit Cell -(BEDT-TSF) 2 GaCl 4  -(BEDT-TTF) 2 Cu(NCS) 2 a = 18 Å b = 16 Å c = 8 Å a = 16 Å b = 8 Å c = 13 Å Layer spacing is the important dimension

The Fermi Surfaces -(BEDT-TSF) 2 GaCl 4  -(BEDT-TTF) 2 Cu(NCS) 2

Anisotropy of the Electronic System  -(BEDT-TTF) 2 Cu(NCS) 2

Molecular Corridor -(BEDT-TSF) 2 GaCl 4

Magnetic Breakdown in  -(BEDT-TSF) 2 GaCl 4

Magnetic Breakdown in  -(BEDT-TTF) 2 Cu(NCS) 2 T = 40 mK T = 650 mK

Magnetic Breakdown Pippard Magnetic Breakdown

Exponential Growth of Breakdown Amplitude

Forbidden Trajectories Anomalous Trajectories are due to Stark Quantum Interference

Angular Dependent Magnetoresistance -(BEDT-TSF) 2 GaCl 4  -(BEDT-TTF) 2 Cu(NCS) 2 B = 42T (DC)

B 

Belly orbits show salt to be more 3-D than  Quasi 2-D region w/B || layers Peak width is determined by the interlayer transfer integral (t ) J. Singleton, et. al. PRL, 88 (2002). C. Mielke, et. al. J. Phys. Cond. Mat., 13 (2001) Tight-binding dispersion relation added to the effective dimer model

Using G-L theory to estimate  z  z ≈ 5Å  z ≈ 16Å

At T*  ≈ 18 Å for -(BEDT-TSF) 2 GaCl 4

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

Superconducting Properties of -(BEDT-TSF) 2 GaCl 4 and  -(BEDT-TTF) 2 Cu(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.

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