Eur. Phys. J. B 58, 263–268 (2007) DOI: 10.1140/epjb/e2007-00221-5 T HE EUROPEAN P HYSICAL JOURNAL B Electronic structure of paramagnetic In 1-x Mn x As nanowires X.W. Zhang a and J.B. Xia Chinese Center of Advanced Science and Technology (World Laboratory), P.O. Box 8730, Beijing 100080, P.R. China and Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, P.R. China Received 21 September 2006 / Received in final form 7 June 2007 Published online 15 August 2007 – c  EDP Sciences, Societ`a Italiana di Fisica, Springer-Verlag 2007 Abstract. The electronic structure, spin splitting energies, and g factors of paramagnetic In1-xMnxAs nanowires under magnetic and electric fields are investigated theoretically including the sp-d exchange interaction between the carriers and the magnetic ion. We find that the effective g factor changes dra- matically with the magnetic field. The spin splitting due to the sp-d exchange interaction counteracts the Zeeman spin splitting. The effective g factor can be tuned to zero by the external magnetic field. There is also spin splitting under an electric field due to the Rashba spin-orbit coupling which is a relativistic effect. The spin-degenerated bands split at nonzero kz (kz is the wave vector in the wire direction), and the spin-splitting bands cross at kz = 0, whose kz -positive part and negative part are symmetrical. A proper magnetic field makes the kz -positive part and negative part of the bands asymmetrical, and the bands cross at nonzero kz . In the absence of magnetic field, the electron Rashba coefficient increases almost linearly with the electric field, while the hole Rashba coefficient increases at first and then decreases as the electric field increases. The hole Rashba coefficient can be tuned to zero by the electric field. PACS. 72.25.Dc Spin polarized transport in semiconductors – 73.21.Hb Quantum wires – 75.75.+a Mag- netic properties of nanostructures 1 Introduction Nowadays, much of the research in semiconductor physics has been shifting towards diluted magnetic semiconduc- tors (DMS) [1–6], as well as their nanostructures [7–14]. These DMS systems can perform spin-dependent ef- fect on electron spin, so have extensive application in spintronics [15,16]. Meanwhile, there has been a growing interest and experimental progress in the one- dimensional semiconductors, which are called nanowires. Nanowires can be grown out of numerous semicon- ductor materials with a large range of radii and by several methods [17–23]. Especially, Mn-doped semicon- ductor nanowires were well synthesized [12–14]. The elec- tronic structure and other properties of DMS nanostruc- tures were studied extensively [7,11–13]. The magnetic field tunable g factor in DMS quantum dots was inves- tigated theoretically [11]. It is expected that the magnetic field tunable g factor will also happen in DMS nanowires. There is another important spin-dependent effect, named Rashba spin-orbit coupling, which is also widely investigated [24–27]. Based on these spin-dependent ef- fects, electron spin might be used in the future to build a e-mail: zhxw99@semi.ac.cn quantum computing devices that combine logic and stor- age functions. One of the most important spin-based de- vices was proposed by Datta and Das [28], which makes use of the Rashba spin-orbit coupling in order to perform controlled rotations of a field-effect transistor (FET) [29]. The Datta-Das device also uses diluted magnetic semicon- ductors as Source and Drain. Recently, people have been paying special atten- tion to the Rashba spin-orbit coupling in semiconductor nanowires [30–40] because of its abundance of physical phenomena. The Rashba spin-orbit splitting [31–37] and spin-polarized transport properties [38–40] of nanowires have been studied theoretically. However, the spin split- ting under both magnetic field and electric field in param- agnetic nanowires and the hole Rashba effect of nanowires are not clear. In this paper, we use the eight-band effective-mass model of semiconductor nanowires, taking into account the sp-d exchange interaction, to study the electronic structure, spin splitting energies, and g factors of param- agnetic In 1−x Mn x As nanowires under magnetic and elec- tric fields. The remainder of this paper is organized as follows. The calculation model is given in Section 2. The results and discussion are given in Section 3. Section 4 is the conclusion.