QFEXT07 Leipzig, Germany, September 17-21, 2007. Recent progress on the precision measurement of the Casimir interaction Ricardo S. Decca Department of

QFEXT07 Leipzig, Germany, September 17-21, 2007.

Recent progress on the precision measurement of the Casimir interaction

Ricardo S. DeccaDepartment of Physics, IUPUI


Daniel López Alcatel-Lucent Technologies

Ephraim Fischbasch Purdue University

Dennis E. Krausse Wabash College and Purdue University

Valdimir M. Mostepanenko Noncommercial Partnership “Scientific Instruments”, Russia

Galina L. Klimchitskaya North-West Technical University, Russia

Eduardo Osquiguil Instituto Balseiro, Argentina. Fullbright Fellow.

NSF, DOE, LANL

Collaborators

Funding


Why does it matter?

• Consequences in nanotechnology (MEMS and NEMS)“Long-range” interaction between moving partsPossibility of controlling the interaction by engineering materials

• Consequences in quantum field theoryThermal dependence

• Consequences in gravitationBackground to measure deviations from Newtonian potential at smallseparations


Outline

• Experimental set-up -Measurement of the force between a Au-coated sphere and a Au-coated plate -Determination of the equivalent pressure between two Au-coated plates -Measurement of the separation between the bodies

• Casimir interaction

• Experimental studies of the PFA

• Future directions -External parameters to change () -Low temperature measurements -Constraints on Newtonian gravitation

• Summary


Experimental setup

bzzzz goimetal


703.4 703.6 703.8 704.0 704.20.0

0.2

0.4

0.6

0.8

1.0

Nor

mal

ized

am

plitu

de

Freq (Hz)

Hzrad10 9

400 600 800 10001E-15

1E-14

1E-13

1E-12

1E-11

F N

/Hz1/

2

Freq (Hz)

22

2

1

41

elth

el

o

B

FFb

AQ

Tk

bF

elF

thF


Dynamic measurements

z

F

I

b C

oor 2

222 1

CC

CC PRz

FERF

22

400 600 800 10000

50

100

150

200

250

PC (

mP

a)

z (nm)

R = 300 m R = 150 m

100 200 300 400 500 600 700 800

-2

0

2

4

6

8

10

P (

mP

a)

z (nm)


Separation measurement

bzzzz goimetal

zg = (2172.8 ± 0.1) nm, interferometer

zi = ~(12000.0 ± 0.2) absolute interferometer

zo = (8162.3 ± 0.5) nm, electrostatic calibration

b = (206 ± 3) m, optical microscope

= ~(1.000 ± 0.001) rad

zg

zmeas is determined using a known interaction

zi, are measured for each position


Distance measurement

Electrostatic force calibration

-15 -10 -5 0 5 10 15 20 250.0

0.2

0.4

0.6

0.8

1.0

(

rad

)

VAu

(mV)

z = 3 mz = 5 m

3.00 3.25 3.50 3.75 4.00 4.25 4.50 4.75 5.00

100

125

150

175

200

225

250

275

300

325

350

Fe (

pN

)

z (m)

V = 0.35 V

V = 0.27 V

)2()( 2

ometalAuoe z

RVVF

Determine:• R• VAu

• o

• ometalzz 2


LC =(775 +/- ) nm (low coherence),

CW 1550 nm (high coherence) in

x

Mirror (v ~ 10 m/s)

x = zi

Readout

- Changes in about 2 nm) give different curves. Intersections provide x

-Quite insensitive to jitter. Only 2x’/(CW)2 Instead of 2x’/CW

(Yang et al., Opt. Lett. 27, 77 (2005)

)2(mod)()(

int4

2

21

xxS

SSz

DDphase

phasefringeCW

i

CWLCD

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

D

= 1.7 nm = -2.1 nm

0 2 4 6 8 10 12 14 16 18 20 22 24-1

0

1

2

3

4

5

6

7

CW

x (m)

Interferometer

Distance measurement


Pressure determination



-Dark grey, Drude model approach-Light grey, Leontovich impedance approach

PRD 75, 077101



Random error

Systematic error

For the first time in our experimentthe random error is smaller than the systematic one



2/32

4)(

pp

TT

eV)1.09.8( p

What are the characteristics of the Au used?

Plasma model

Leontovich impedance


Proximity force approximation

z

F

RR

zzPRzP

R

zzRRzF

Cppeff

ppCasimirC

2

1...1)(,

...12,

'

Measurements as a function of R

10.5 m31.4 m52.3 m

102.8 m148.2 m

400 600 800 10000

50

100

150

200

250

PC (

mP

a)

z (nm)

R = 300 m R = 150 m



Insets:Fits at z =170 nm

Yield the slopes ’

z

F

RR

zzPRzP

R

zzRRzF

Cppeff

ppCasimirC

2

1...1)(,

...12,

'



’(z<300 nm)| < 0.4

Not so clearwith

If we assume the ideal case situation,

|(z<300 nm)| < 0.6


Future work

• External parameters to change ()Negative index of refraction materialsMagnetic field in manganitesQuantum Hall effect

• Thermal dependenceCheck for consistency between models by lowering the temperature

• Corrections to Newtonian gravitationCheck upturn observed at low separationsContinue building new system for “Casimir-less”measurements


-Reduce background

What’s next?

Si

Ti

Si

Si

Ti

Si

Si

Ti

Si Au

Si

Ti

Si Au

Glass

Au

Ti

Si Au

Glass

r/n

-Improve signal


1 0

- 7

1 0

- 6

1 0

- 5

1 0

- 4

1 0

2 0

1 0

1 6

1 0

1 2

1 0

8

1 0

4

1 0

0

5

3

4

m e t e r s

1

Gau ged Baryon s

Excludedby

exper im ents

Glu

on

mod

ulus

2

Str

ang

e m

od

ulu

s

Two orders of magnitude improvement

About four orders ofmagnitude improvement


Summary

• Random errors smaller than systematic ones

• Improved agreement with theory

• Experimental investigations to test PFA

• Continued effort towards a more sensitive “Casimir-less” experiment



Jonathan L. Feng, Science 301, 795

(’03)

The strength of gravity for various numbers of large extra dimensions n, compared to the strength of electromagnetism (dotted)

Without extra dimensions, gravity is weak relative to the electromagnetic force for all separation distances.

With extra dimensions, the gravitational force rises steeply for small separations and may become comparable to electromagnetism at short distances.

What is the background?


Proximity force theorem

a

k,4

122

kCC hRERF

CE : energy density

R

Believed to be exact for Casimir interaction. Proved to produce errors smaller than a/R ~ 1/1000


bQf

TkF

r

B 12

serp

Sis L

Ewt

6

3

t

w

L

tEw Sir 3

2 3

w, t = 2m

40r

s


vi: Fraction of the sample at separation zi

)(zFvF CSi

iC

AFM image of the Au plane

Documents

QFEXT07 Leipzig, Germany, September 17-21, 2007. Recent progress on the precision measurement of the Casimir interaction Ricardo S. Decca Department of