1. L. Besombes et al., PRL93, 207403, 2004 Single exciton spectroscopy in a semimagnetic nanocrystal J. Fernández-Rossier Institute of Materials Science, University of Alicante, SPAIN Talk available in: www.ua.es/jfrossier/personal Absorption Emission CdTe nanocrystal CdTe nanocrystal+ 1Mn Goal: Calculate PL and quantum information Spin relaxation PL 6 N Mn S=5/2 2S+1=6

2. Method : 1)Calculation of one-body wave functions (for a given dot) 2)Evaluation of many body exciton- Mn spin Hamiltonian 3)Exact diagonalization of GSM 4)Exact diagonalization of XSM 5)Linear reponse theory Ground State Manifold (GSM) Exciton States Manifold (XSM) 4x6 N 6N6N +1+2 1 4 N Mn GSM Qbits 162 2365 32167 4 1296 10

3. FORMALISM Ground State Manifold (GSM) 4  6 N e h Exciton States Manifold (XSM) 6N6N SPIN ORBIT INTERACTION Heisenberg Ising

4. Valence band Spin orbit: Ising coupling SHAPE MATTERS: Quenching of transverse Hole-Mn exchange

5. GSM and XSM spectrum E(meV) 1 Mn NG=6 NX=24 2 Mn NG=36 NX=244 3Mn NG=216 NX=864 E(meV) Magnetic Field (0,0,5)

6. Photoluminescence (PL) Theory Spontaneous Emission from X to G Energy conservation Optical Selection rules SPIN BLOCKADE PL SPECTRUM Occupation of excited state Thermal like occupation Energy (meV) PL, theory PL, experiment PL: results

7. OPTICAL SPIN BLOCKADE Franck Condon= Spin Blockade Standard optical selection rule GSM XSM Photon measurement= SPIN MEASUREMENT 24*6=144 XSM to GSM Only 12 are allowed

8. PL, experiment N=3. Narrowing and shift 0T 2T 4T 6T 8T 10T P. S. Dorozhkin, Phys. Rev. B 68, 195313 (2003)

9. Conclusions Model Hamiltonian gives good account of PL experiments: –Single Mn –Broadening and narrowing of lines –Voigt wider than Faraday Optical detection of quantum state of N=1,..4 spin S=5/2 in semiconductor nanocrystal. Related papers: 1)JFR, in preparation 2)JFR, L. Brey, Phys. Rev. Lett. 93 117201 (2004) 3)G. Chiappe, JFR, et al, Condmat/0407639