Physica B 249—251 (1998) 171 — 174 Polarization anisotropy and Zeeman splitting in strained quantum wires: Dimensional crossover effect on strain M. Notomi*, J. Hammersberg, J. Zeman, H. Weman, M. Potemski, H. Sugiura, T. Tamamura  NTT Opto-electronics Labs. 3-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-01, Japan  Department of Physics, IFM, Linko ( ping University, S-581 83, Linko ( ping, Sweden  Grenoble High Magnetic-Field Lab. CNRS and MPI-FKF, 25 avenue des Martyrs, Grenoble, F-380 42, France Abstract Strain states in lattice-mismatched quantum wires have been studied by polarization analysis with a high magnetic field. Although biaxial strain should suppress quantum-confinement-induced in-plane linear polarization, large polariza- tion is observed. This polarization remains even at a very high magnetic field, which shows that polarization is caused by non-biaxial (anisotropic triaxial) strain states in which the symmetry of the strain is broken. Circular polarization experiments show that Zeeman splitting is highly nonlinear to the field, which is also explained by the non-biaxial nature. These results can be understood as dimensional crossover on strain.  1998 Elsevier Science B.V. All rights reserved. Keywords: Strained quantum wire; Zeeman splitting; Magneto-photoluminescence In the last decade, various kinds of lattice- mismatched multi-dimensional quantum structures (strained quantum wires/dots) have been fabricated and studied, but most of the attention has been paid to their low-dimensional effects due to quan- tum confinement (QC), and strain has been as- sumed the same as that in films in most cases. However, strain itself in these structures, in prin- ciple, should be qualitatively different from that in strained film [1,2]. Strain of films is uniform within a film and zero in the surrounding area. Strain of wires, however, is highly non-uniform and the bar- * Correspondence address. NTT Opto-electronics Labs. 3-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-01, Japan. Fax: #81 462 40 4305; e-mail: notomi@aecl.ntt.co.jp. rier region is also deformed. Fig. 1 shows a cal- culated strain distribution of lattice-mismatched quantum wires. This shows that the strain of wires is qualitatively different from that of films. In a dif- ferent view, this change can be regarded as a dimen- sional crossover concerning strain since it orig- inates from the dimensionality of the elasticity problem. The strain in films is conventionally character- ized as biaxial, which means constraints exist only in two axes and the remaining axis is free. We hereafter call the strain state in wires as anisotropic **tri-axial++ because constraints exist in three axes and the in-plane translation symmetry is broken. Recently, such a non-biaxial nature of strain 0921-4526/98/$19.00  1998 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 5 2 6 ( 9 8 ) 0 0 0 9 2 - 1