iron-type superconductors presentation

8/12/2019 Iron-type superconductors presentation

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Academia Sinica ()

Institute of Physics ()

Grace Lei, Alexander Tseng, Debby Hsu


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Or, we paraphrase out of a textbook (and also Wikipedia) (butshhh, dont tell)


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Any material that has the two following properties:

Zero resistivity (R), aka infinite conductivity, below acertain temperature, TC(critical temperature)

Perfect diamagnetism, aka zeromagnetic induction (B),

below the specific TC

That levitating piece ofmaterial that our physics

professors showed us in class.----The extent of our knowledgeon superconductors before

our internship.


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Materials resistance to flow of electric current.

Theoretically, for superconductors:

Any current flowing through the material will notexperience decay in any way.

If a current was inducedin a closed loop ofthe material cooledbelow its TC, the current

would never stop flowing.

Thats basically perpetual motion!


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Magnetic induction is zeroperfect diamagnetism

Meissner Effect!


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Most metallic elements But usually not magnetic ones (Fe, Co, Ni, etc)

Permanent magnetic moments destroysuperconducting ordering

Binary alloys/compoundstransition metals + otherelements

Certain organic compounds

First one discovered in 1980: [TMTSF]2PF6 TMTSF = teteamethyltetraselenafulvalene

Try saying that three times fast

Typically bad room temperature conductors

Require strong phonon-electron coupling


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BCS Theory (Bardeen-Cooper-Schrieffer)

Cooper Pairings

Phonons

To answer that question requires years and years ofgraduate-level math and knowledge, so I dont know why

youre asking us.


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In the medical field: MRI, NMR

In the technology field: Wires, high speed

computers, frequencyfilters (for mobile phonesand antennas)

In the science field: SQUID, giant particle

accelerators, stabilizers insatellites

In the industrial field: Maglev trains,

electric motors and

generators, devices todisable bombs

In everyday life: BUCKYBALLS, digital

routers for super fastInternet

And in many other devicesand systems.


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Room temperature superconductors

Or at least 273K (0C) superconductors

The temperature atwhich scientists wouldlove to see the Tcforsuperconductors.


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We didnt just spend two months partying, Ill have you know.


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Superconductivity in Fe-based compounds challengesconventional wisdom.

Fe is ferromagnetic

Simpler doping system may reveal clues to the

microscopic theory.

Superconductivity discovered in bulk form FeSeintercalated with Li and pyridine. Krzton-Maziopa, A., Pomjakushina, E. V., Pomjakushin, V. Y., von Rohr, F.,

Schilling, A., & Conder, K. (2012). Synthesis of a new alkali metal-organicsolvent intercalated iron selenide superconductor with tc{\approx}45k. doi:arXiv:1206.7022v1


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Bulk Nanoparticles

FeSe, FeSeTe, FeTeS


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SuperconductingQUantum InterferenceDevice

Measures TCfrom themagnetic flux

Graphs susceptibilityversus temperature

Instruments


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Uses x-rays to identifya materials crystalstructure

Instruments


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Instruments


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Evacuated tube, filled with nitrogen

Prevents oxidation

Instruments


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Stainless steal

Instruments


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Instruments


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We love the glove box because it prevents our materials

from oxidizing.


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And the glove box loves us too :D


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Iron precursors created by combining the isolated

powder elements in proportion.


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Iron mixtures compressed into blocks and then

vacuum-sealed into tubes.


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Iron mixtures then underwent 3 stages of

sintering.


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Between each stage of sintering, the compounds

were ground into a powder and then recompressed

into blocks.


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Iron mixtures then underwent sintering in

nitrogen-filled Swagelok tube furnace.


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Iron compounds

left to soak in a

liquid solution to

intercalate lithium

and pyridine into

the compounds.


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Materials are then annealed.


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Products TCevaluated via susceptibility (SQUID)

and resistance testing.


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At each stage (after sintering, after intercalation, afteranneal) in both experiments, samples were taken for: XRD testing to verify crystal structure.

SQUID testing to check superconductivity. Sintering

Intercalation

Annealing


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Or, we dont know what the hell were doing but heres somepretty graphs that are supposed to mean something significant.


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Nanoparticles


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10 20 30 40 50 60 70

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

(004)H(113)(211)

(103)

(200)

(112)

(102)H(111)

(002)H

(101)

Intensity(a.u.)

2

Original

Int ercalation

Annealed 36hr

Annealed 72hr

(001)

FeSe Series


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0 50 100 150 200 250 300

0.0

0.2

0.4

0.6

0.8

1.0

Li (C5H

5N)FeSe_Annealed 72 Hrs

Tempera ture (K)

normalized)

1000 Oe

500 Oe

100 Oe

30 Oe

0 10 20 30 400.0

0.6


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Nanoparticles


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10 20 30 40 50 60 70

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

FeSe0.3

Te0.7

Series

(201)(211)(200)

(112)

(102)

(111)(110)(002)

(101)

Intensity(a.u.)

2

Original

Intercalation

Annealed 36hr

Annealed 72hr

(001)

10 20 30 40 50 60 70

0

1000

2000

3000

4000

FeTe0.8

S0.2

Series

(202)

(211)

(201)(200)

(112)

(102)

(111)(110)(002)

(101)

Intensity(a.u.)

2

Original

Intercalation

Annealed 36hr

Annealed 72hr

(001)


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0 50 100 150 200 250 300-1.0

-0.5

0.0

0.5

1.0

1.5

FeSe0.3

Te0.7

_Original

Temperat ure (K)

(10-3emu/g*Oe)

30 Oe

TC= 13.27K

0 50 100 150 200 250 3002.2

2.4

2.6

2.8

3.0

3.2

3.4

3.6

3.8

4.0

FeTe0.8

S0.2

_Original

Temperature (K)

(10-4emu/g*Oe)

30 Oe

TC= 28.66K


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0 50 100 150 200 250 300-4

-2

0

2

4

6

Li(C5H

5N)FeSe

0.3Te

0.7_Interc alated

Temperature (K)

(10-3emu/g*Oe)

30 Oe

TC13.03K

0 50 100 150 200 250 3000.0

0.5

1.0

1.5

2.0

2.5

Li (C5H

5N)FeTe

0.8S

0.2_Interc alated

Temperat ure (K)

(10-3emu/g*Oe)

30 Oe

Tc 60K


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0 50 100 150 200 250 300

0.5

0.6

0.7

0.8

0.9

1.0

Temperatur e (K)

(normalized)

Li(C5H

5N)FeTe

0.8S

0.2_Annealed 72 Hrs

30 Oe

100 Oe500 Oe

1000 Oe

0 50 100 150 200 250 300

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Temperatur e (K)

(normalized)

Li(C5H

5N)FeSe

0.3Te

0.7_Annealed 72 Hrs

30 Oe500 Oe

1000 Oe

?


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0 50 100 150 200 250 3001.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

Li(C5H

5N)FeTe

0.8S

0.2_Anneale d 72 Hrs

Temperatur e (K)

Resistance(Ohm)

0 50 100 150 200 250 300

10

12

14

16

18

20

22

24

26

Temperat ure (K)

Li(C5H

5N)FeSe

0.3Te

0.7_Annealed 72 Hrs

Resistance(Ohm)


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Different molar ratios of FeTeS (more potential) FeTe0.3S0.7 , FeTe0.5S0.5, FeTe0.7S0.3

Different iron-based compounds

FeTe

Different alkali metals (1stgroup on periodic table)

Different annealing times

Different soaking times

Different sintering temperatures/times/rates Finer measurements


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National Science CouncilAcademia Sinica Institute of Physics

Professor Maw-Kuen Wu

Maverick HsiehAll PH.Ds and Research Assistants at the

Superconductor Laboratory

Special Shoutout to C. C. Chang, C. H.Hsu, Y. R. Wu, M. H. Wen


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Alright, if you really want to ask more questions well providesome visuals, though why you would want to stay here longer,

well never know.


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Sintering: Makes the mixed powder into a compound. Based on atomic diffusion Heated to temperature below melting point (usually). Atoms in the powder diffuse across boundaries of particles,

bonding together, making one solid piece. Also anneals a little bit at the same time.

Annealing: Melting the compound and recrystallizing for nanoparticles. Occurs by diffusion of atoms within a solid material, so that

material progresses towards equilibrium state. Bonds are broken (energy provided by heat) and recrystallized. Also normalizes the sample by refining the grains and

producing a more uniform and desirable size distribution.


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0 50 100 150 200 250 3000.4

0.5

0.6

0.7

0.8

0.9

1.0

Tempera tur e (K)

Li(C5H

5N)FeTe

0.8S

0.2_Annealed 36 Hrs

120K

(normalized)

25 Oe

100 Oe

TC39.42K

0 50 100 150 200 250 300-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Temperat ure (K)

Li(C5H

5N)FeSe

0.3Te

0.7_Annealed 36 Hrs

(normalized)

15 Oe100 Oe

1000 Oe

?

iron-type superconductors presentation

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