Transcript of Sasha Kuntsevich Nimrod Teneh Vladimir Pudalov Spin-droplet state of an interacting 2D electron...
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- Sasha Kuntsevich Nimrod Teneh Vladimir Pudalov Spin-droplet
state of an interacting 2D electron system M. Reznikov Magnetic
order in clean low- density systems Methods of magnetization
measurements Recharging Technique Experimental results Implications
Technion
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- Electron gas with interactions Short range repulsive
interaction 2nd order phase transition into ferromagnetic ordered
state For a single-valley system Stoner (1947) Stoner
instability
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- Ferromagnetic Bloch Instability Decreasing density Energy
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- Phase diagram Attaccalite et al. (2001) First order transition
at r s ~20: Senatore et al. (2001) r s ~26
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- Clean system B. Tanatar and D.C. Ceperley (1989)
ferromagnetic
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- Clean system Very small energy difference! antiferromagnetic
ferromagnetic B. Tanatar and D.C. Ceperley (1989)
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- Methods: Shubnikov - de Haas beatings F. Fang and P. Stiles
(1968), T. Okamoto at al., (1999), S. Vitkalov at al. (2000), V.
Pudalov at.al., (2001) 2 4 6 7 rsrs
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- V. Pudalov at al, (2001) Metal-Insulator Transition in a
Silicon Inversion Layer gg
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- In-plane magnetoresistance S. Vitkalov et al. PRL 2001A.
Shashkin et al. PLR, 2001
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- In-plane magnetoresistance A. Shashkin et al. PLR, 2001
Possible FM transition ??
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- Samples: Si Field effect transistors Russian samples, beginning
of 80 th, Holland samples, mid 80 th Typical parameters 3.4 x10 4
cm 2 /Vs @1.7K
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- The Principle of the Recharging Technique Maxwell relation:
Small correction
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- Diamagnetic contribution Capacitance contribution
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- Recharging Technique _ + VGVG Out Modulated magnetic field B+
Current Amplifier Ohmic contact Gate SiO 2 Si 2D electron gas
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- Expected behavior T=0, finite magnetic field gg Interactions M
n No interactions n Interactions Prus et al,2003 B>T
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- B (T) g B B~2E F kT/4
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- Raw data, low fields Compare with single spins M/n= B tanh(b),
b=g B B/2T
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- 1
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- The same characteristic magnetic field
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- Interactions n n No interactions Interactions d /dn(n),
expectations
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- d /dn(n), T=1.7-13K
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- d /dn(n), T=0.6-4K
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- vs. Temperature
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- (n), T=1.7-13K
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- Magnetic moment at B=2T
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- Comparison with Transport Measurements
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- Main observations Possible scenario: few electron droplets
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- Droplet scenario vs theory Fermi-liquid expectations:
Spontaneous large spin droplets in disordered metal Diffusion
enhanced interactions in quantum dots Mean Field treatment:
Andreev, Kamenev (1998) Numerics: Shepelyansky (2001) Narozhny, B.
N. and Aleiner, I. L. and Larkin, A. I. (2000)
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- Conclusion: Problems :
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- Problem O. Prus, Y. Yaish, M. Reznikov, U. Sivan, and V.
Pudalov, PRB 2003 : Assumption: at large density the susceptibility
is the renormalized Pauli one This assumption happened to be
wrong!
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- Old results (Prus et al, 2003)
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- Field dependence of the magnetic moment
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- In-plane magnetoresistance A. Shashkin et al. PLR, 2001Fleury,
Weintal, 2010.
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- Raw data
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- Susceptibility in at B=2T
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- d /dn(n), Holland sample
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- Stoner Ferromagnetic Instability Stoner (1947) Finkelstein
(1983) For a short range repulsive interaction Diffusion enhanced
interactions in quantum dots Mean Field treatment: Andreev, Kamenev
(1998) Numerics: Shepelyansky (2001)
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- Clean system Very small energy difference! antiferromagnetic
ferromagnetic A. Finkelstein (1983), Castellani at al.,(1984)
Shekhter, A. and Finkel'stein, A. M (2005) B. Tanatar and D.C.
Ceperley (1989)
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- Real system S=0 Bhatt and Lee (1982)
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- Real system S=0 Bhatt and Lee (1982)
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- Real system S=0 Bhatt and Lee (1982) Andreev, A. V. &
Kamenev, A. (1998) Kurland, I. L. and Aleiner, I. L. and Altshuler,
B. L. (2000)
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