single electron transport in diluted magnetic semiconductor quantum dots department of applied...

Single electron Transport in diluted magnetic semiconductor quantum dots

Department of Applied Physics, U. Alicante SPAINMaterial Science Institute of Madrid, CSIC SPAIN

J. Fernández-Rossier, R. Aguado

www.ua.es/personal/jfrossier/

Spin dependentCapacitance

Z19-1

Gate Tuning Anisotropy

CdTe+1 Mn

GaMnAs Single electron transistor

cond-mat/0602608 Coulomb blockade anisotropic magnetoresistance: Single electronics meets spintronicsAuthors:J. Wunderlich et al.

Mn(2+)

S=5/22S+1=6

PL

Int

ensi

ty

www.ua.es/personal/jfrossier/

Y. Léger et al., PRL 95, 047403 (05)L. Besombes et al. PRL 93, 207403 (04)

Single ExcitonSpectroscopy

1 Mn per dot

MSJMSJHH eezzheh

0

ST=Se+M

Heisenberg

Ising

25zM

21zM

23zM

Mzhe JJ

Single exciton spectroscopy (1 Mn dot)

EXPERIMENTS:Y. Léger et al. PRL 95, 047403 (05)

THEORY: J. Fernández-Rossier, PRB73, 045301 (06)

WE UNDERSTAND e+h+Mn

NENH Ndot

Theory I: The dot STATES

MSffJffVH vvvvvv

vvv

nnGvdot

','

',',

NUMERICAL DIAGONALIZATION

STATES WITH a FIXED NUMBER of CARRIERS (Controlled By Gate Voltage)

GATE CONTROL of Magnetic Anisotropy

Heisenberg

ST

Q=-1 Q=0 Q=+1 Q=+3

Free

HHLH

Ising ZXX

Mz

KL

LKNMKLMNMN RHi

dt

d,,

, ,

tunneldrainsourcedot VHHHH

N

NNNNNNNNI ,11,11,,

MASTER EQUATION

Scattering Rates

Theory: Single electron transport

Density matrix (Vg, Vb)

2

1, 1 NdNNN

CHARGING the dot

E

Q=0

Q=1

Q=2

VG

VG

Q

Q=0Q=1

Q=2 G

CHARGING the dot

S=3

S=2

Spin dependentCHARGING

ENERGY

3 PEAKS instead of 1 !!

2/5 2/5

2/3 2/3

2/1 2/1

2/1 2/1

2/3 2/3

2/5 2/5

VG

E

25zM

21zM

23zM

2/5 2/5

2/3 2/3

2/1 2/1

2/1 2/1

2/3 2/3

2/5 2/5

VG

E

25zM

21zM

23zM

2/5 2/5

2/3 2/3

2/1 2/1

2/1 2/1

2/3 2/3

2/5 2/5

VG

E

25zM

21zM

23zM

2/5 2/5

2/3 2/3

2/1 2/1

2/1 2/1

2/3 2/3

2/5 2/5

VG

E

Q=0

2/5 2/5

2/3 2/3

2/1 2/1

2/1 2/1

2/3 2/3

2/5 2/5

VG

E

Q=1/3

2/5 2/5

2/3 2/3

2/1 2/1

2/1 2/1

2/3 2/3

2/5 2/5

VG

E

Q=2/3

2/5 2/5

2/3 2/3

2/1 2/1

2/1 2/1

2/3 2/3

2/5 2/5

VG

E

Q=3/3

Inelastic single spin spectroscopy

CONCLUSIONS

Electric Tuning of magnetic anisotropy

Ising ZXX

Mz

www.ua.es/personal/jfrossier/

SPIN conditional charging energy

Q=+1 Q=+3