Electron-Phonon Interaction in the Polymeric

Superconductor, Polysulfur Nitride, (SN)x

Paul M. GrantIBM Research Staff Member, Emeritus

Session P8: Focus Session: Novel Superconductors: Miscellaneous Materials

2007 APS March MeetingTalk P8.00007, 12:39 PM – 12:51 PMWednesday, 7 March, CCC Korbel 1C

Denver, Colorado

http://www.w2agz.com/snxaps07.htm

1975: Superconductivity Discovered at 300 degrees in

Polysulfurnitride, (SN)x…but the units are in millikelvin !

Precursor to a Nobel Prize

“Thanks,” “Grazie,” & “Hvala Lepa” to…

• Paolo Giannozzi and his team at CNR-INFM-Democritos for developing and supporting PWscf and Quantum-Espresso

• Anton Kokalj of the Jozef Stefan Institute, Slovenia, for PWgui and XCrySDen

• The UK Cambridge crystal structure data base team for developing and support of the Mercury crystal imaging package

…and all this for free! A paradigm for a future world order?

Structure of (SN)x

Cohen, et al., JACS 98, 3844 (1976)

• Monoclinic P21/c

• a=4.485, b=3.767, c=8.452, =106.43

• 4 N, 4 S, 2 chains• S=32.06, N=14.007• S[Ne]3s23p4,

N[He]2s22p3

• 44 electrons• 22+ bands• Many phonon IRs

(12-24)

b-axis unique

ZE

U

A

b-axis unique(but same notation

for c-axis)

Z E A U

eV

EF

Band Structure of (SN)x

-25

-20

-15

-10

-5

0

5

0 1 2 3 4 5 6

DOS (electrons/eV)

En

erg

y (

eV

)

Electrons

Holes

Electron-Phonon Coupling

Wierzbowska, et al., arKiv.cond-mat/0504077

“Experimental Apparatus”

• Linux box running SUSE 10.1• Dual Xeon (1.2 GHz) Motherboard, 2 GB

RAM, 133 MHz FSB, Vintage ca. 2003• Democritos Quantum Espresso Package

– Vanderbilt US pseudopotentials for N & S– pw.x, 4x4x4 MP grid– ph.x, tr2_ph = 1e-11 |ddv_scf|^2– 1 q-point => 25 hours wall time– Still not a fully converged calculation!

Omega vs Representation

-5

0

5

10

15

20

25

1 3 5 7 9 11 13 15 17 19 21 23

Representation Index

THz

B_u 1A_u 2A_g 3B_g 4B_u 5B_g 6A_u 7A_g 8A_u 9A_g 10B_u 11B_g 12B_u 13B_g 14A_u 15A_g 16B_u 17B_g 18A_u 19A_u 20A_g 21A_g 22B_u 23B_g 24

DOS

0

5

10

15

20

25

0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Gauss Factor (Ry)

stat

es/s

pin

/Ry/

un

it c

ell

Fermi Energy

2.532.542.552.562.572.582.592.6

2.612.622.63

0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Gauss Factor (Ry)

Ef

(eV

)

Total Lambda (q = 0,0,0 (Gamma))

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Gauss Factor (Ry)

lam

bd

a

Exp

To-Do List

• Get access to some more flops (BlueGene?)

• Compute “nesting vectors”

• Compute Eliashberg and compare with Binnig tunneling

• Compute full lambda• Dope (e.g., Br & ?)