INFM DMF INFMeeting, Genova 23-25 Giugno 2003 EFFECTIVE MASS AND MOMENTUM RESOLVED INTRINSIC LINEWIDTH OF IMAGE-POTENTIAL STATES ON Ag(100) INFM and Università Cattolica del Sacro Cuore Dipartimento di Matematica e Fisica, Via Musei 41 Brescia. Claudio Giannetti
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INFMDMF INFMeeting, Genova 23-25 Giugno 2003 EFFECTIVE MASS AND MOMENTUM RESOLVED INTRINSIC LINEWIDTH OF IMAGE-POTENTIAL STATES ON Ag(100) INFM and Università
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INFM DMF
INFMeeting, Genova 23-25 Giugno 2003
EFFECTIVE MASS AND MOMENTUM RESOLVED INTRINSIC LINEWIDTH OF IMAGE-POTENTIAL
STATES ON Ag(100)
INFM and Università Cattolica del Sacro Cuore
Dipartimento di Matematica e Fisica, Via Musei 41 Brescia.
Claudio Giannetti
INFM DMF
INFMeeting, Genova 23-25 Giugno 2003
•Femtosecond Laser and tunability of photon energy
→ Non-Linear Photoemission
•Study of image-potential states on Ag(100) at different photon energies: effective masses and lifetimes.
INTRODUCTION
•WHY IMAGE POTENTIAL STATES?
Relaxation of electrons into bulk states can be studied directly in the time-
domain with pump-probe techniques.U. Höfer et al., Science 277, 1480 (1997).W. Berthold et al., Phys. Rev. Lett. 88, 056805 (2002).
It is a many body interesting problem.A.García-Lekue et al., Phys. Rev. Lett. 89, 096401 (2002).J. Kliewer et al., Science 288, 1399 (2000).
Interplay between image-potential states and dynamics of molecules at surfaces.A. D. Miller et al., Science 297, 1163 (2002).
* K.Giesen et al., PRB 35 975 (1987).** Z.Li and S.Gao , PRB 50 15349 (1994).
n=1n=1
n=2 n=2
INFM DMF
INFMeeting, Genova 23-25 Giugno 2003
Gaussian: experimental resolution FWHM45meV
Lorentzian: intrinsic linewidth 14meV @ k//=0
/
IS LIFETIMES
FITTING: Gaussian-Lorentzian convolution
LIFETIME
Linewidth dependance on k//
Measured values (fs) Calculated values (fs)
n=1 n=2 n=1 n=2
47±7 ≥5555±5# 160±10#
55## 132###
# I.L.Shumay et al., PRB 58 13974 (1998).## A.García-Lekue et al., Phys. Rev. Lett. 89, 096401 (2002).### E.V Chulkov et al., Surf. Sci 391 L1217 (1997).
fs658meV
INFM DMF
INFMeeting, Genova 23-25 Giugno 2003
heVE
FIRST OBSERVATION OF IMAGE STATES OUT OF RESONANCE
EEV
EF
n=1
e-
E=3.8 eV
0.5 eV
Ekin= h-Ebin= (3.14-0.5)eV 2.7eV
e-
LINSCALE
Fermi edge
inte
nsit
y
Ekin (eV)
LOGSCALE
Fermi edge
inte
nsit
y
Ekin (eV)
INFM DMF
INFMeeting, Genova 23-25 Giugno 2003
DISPERSION AND SELECTION RULES
m*/m0.95
n=1
Fermi edge
Ekin= h-Ebin
h=0.39eV
h=3.15eV h=3.54eVEV
EF
n=1e-
Ebin
INFM DMF
INFMeeting, Genova 23-25 Giugno 2003
SELECTION RULES
DIPOLE SELECTION RULES:
J=0 in S-polarizationJ≠0 in P-polarization
n
P
S
Ag(100)
WHICH IS THE POPULATION AND PHOTOEMISSION MECHANISM?
We can exclude:
Role of surface roughness
Ponderomotive and tunnel effects at the surface,
because the radiation intensity is too low. (I~0.1GW/cm2)
INFM DMF
INFMeeting, Genova 23-25 Giugno 2003
CONCLUSIONS
•Non-linear photoemission on image-potential states in Ag(100).
• Improvement of the precision in the measurement of the effective masses and lifetimes.
• Observation of image-potential states also when hE1-Efermi. In this case the image-potential states can be populated and photoemitted also in S-polarization.
INFM DMF
INFMeeting, Genova 23-25 Giugno 2003
Responsibles:
F. Parmigiani, G. Ferrini.
Co-workers:
F. Banfi, D. Fausti, G. Galimberti, S. Pagliara, M. Peloi.