Bulletin of the American Physical Society
APS March Meeting 2012
Volume 57, Number 1
Monday–Friday, February 27–March 2 2012; Boston, Massachusetts
Session P14: Focus Session: Spins in Semiconductors - Quantum Dots and Qubits
8:00 AM–11:00 AM,
Wednesday, February 29, 2012
Sponsoring Units: GMAG DMP FIAP
Chair: Connie Li, Naval Research Laboratory
Abstract ID: BAPS.2012.MAR.P14.1
Abstract: P14.00001 : Magnetic Polarons and Bipolarons in Quantum Dots*
8:00 AM–8:36 AM
Preview Abstract Abstract
(University at Buffalo)
Magnetically doped (typically by Mn) semiconductor quantum dots (QDs) allow a control of magnetic ordering in ways not available in the bulk. For example, onset of magnetism can be realized by adding a single carrier or changing symmetry of the quantum confinement, even at a fixed carrier number . Recent experiments revisit the concept of magnetic polaron , formed when a single carrier added to a QD aligns the Mn spins through exchange interaction. The experiments [3,4] show that the induced magnetization persists at relatively high temperatures. First, we discuss a QD system, in which the experimental magnetic polaron energy, in addition to its relatively high value, shows a surprisingly weak temperature dependence . We explain this effect by magnetic anisotropy of the QD. Next, we turn to the case where a magnetic QD contains two carriers. We find theoretically that Mn spins align, forming a magnetic 'bipolaron', even when the ground state has zero carrier-spin . The corresponding state breaks spatial symmetry, unlike in the case of a single magnetic polaron. We propose experimental tests of our prediction. We also explore the stability of the broken-symmetry state with zero net magnetization versus other patterns of magnetization . Finally, we show some interesting consequences of diffusive coupling of a magnetic QD to a reservoir of carriers . This work was done in collaboration with P. Stano, J. Pientka, A. Petukhov, and I. Zutic.\\[4pt]  R. M. Abolfath, et al. Phys. Rev. Lett. 101, 207202 (2008).\\[0pt]  Maksimov, A. et al. Phys. Rev. B 62, R7767 (2000), J. Seufert et al., Phys. Rev. Lett. 88, 027402 (2002).\\[0pt]  R. Beaulac et al., Science 325, 973 (2009).\\[0pt]  I. R. Sellers, et al., Phys. Rev. B 82, 195320 (2010).\\[0pt]  R. Oszwaldowski, et al., Phys. Rev. Lett. 106, 177201 (2011)\\[0pt]  P. Stano, R. Oszwaldowski, A. G. Petukhov, and I. Zutic, preprint.\\[0pt]  J. M. Pientka, R. Oszwaldowski, A. G. Petukhov, J. E. Han and I. Zutic, Reentrant Magnetic Polaron Formation in Quantum Dots, preprint.
*Supported by DOE-BES, U.S. ONR, AFOSR-DCT, NSF-ECCS, and CAREER.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2012.MAR.P14.1
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