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Magnetoelectronic properties of finite carbon nanotubes (CNs) are studied for an arbitrary field direction. They are strongly affected by the nanotube geometry (length, radius; boundary structure), the magnitude and direction of the magnetic field, the Zeeman effect, and the temperature. Geometric structures determine electronic structures and magnetic properties, which thus leads to three types of energy gaps and induced magnetic fields. The critical angle, which corresponds to the change of magnetism, exists in armchair CNs, but not in zigzag CNs. It also depends on the length and the radius of CNs. Finite CNs are very different from infinite CNs. Zeeman splitting could induce complete energygap modulation, a drastic change in magnetization, and a gigantic paramagnetic response for all zigzag CNs. The predicted results are observable even at room temperature.Quasi-one-dimensional carbon nanotubes (CNs) 1) have attracted much attention due to their very interesting properties and high potential for practical applications. A single-walled CN is a rolled-up 2D graphite sheet in the cylindrical form. By cutting a very long CN into a shorter one, a quasi-zero-dimensional finite CN is obtained. A scanning tunneling microscope has been utilized to produce finite CNs with length w $ 100 # A.2) The quantum-size effects cause finite CNs to exhibit special physical properties, e.g., geometric structures, 3) electronic structures, 4-7) optical properties, 8,9) magnetic 10-12) and quantum transport properties. 13) Many theoretical and experimental studies had been carried out on magnetoelectronic properties of infinite CNs. 14-21) Without a magnetic field B, whether CNs are metallic or semiconducting depends on their radius, chirality, and curvature effects. For example, (m, m) armchair CNs, 20) (m ¼ 3I, 0) zigzag CNs, and (m 6 ¼ 3I, 0) zigzag CNs are, respectively, gapless metals, narrow-gap semiconductors, and moderate-gap semiconductors (I is an integer). Infinite CNs drastically change from metals to semiconductors or vice versa, when they exist in a uniform magnetic field. 16) From the theoretical predictions, 17,18) the metallic and narrow-gap (moderate-gap) systems are paramagnetic (diamagnetic) with magnetic field parallel to the nanotube axis (B k kẑ z). All infinite CNs are diamagnetic in the presence of the perpendicular magnetic field (B ? ). Moreover, the dependence of the magnetic response on the radius is very weak.In this work, the tight-binding model with the curvature effects is used to study magnetoelectronic properties of finite CNs with any field direction. The dependence of magnetoelectronic properties on the magnitude (B) and direction () of the magnetic field, the geometric structures (length, radius r; boundary structures), Zeeman splitting, and the temperature (T) are investigated. Comparison with results for infinite CNs are also performed.Finite armchair and zigzag CNs are chosen for a model study. An armchair and a zigzag CN, as shown in Figs. 1(a) and 1(b), respectively, is obtained by rolling ...

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Magneto-electronic properties of AA-stacked graphene superlattice (simple hexagonal graphite) are studied by the tight-binding model with an exact diagonalization method. The Landau subbands (LSs) with strong energy dispersions exist along k(z) and each subband possesses two band-edge states. Density of states reflects main features of the LSs, such as asymmetric prominent peak structures and the semimetallic behavior. Under the AA-stacked configuration, the LS wave functions are characterized by two sublattices, a and b. The quantum number (n(c,v)) of each LS, which corresponds to the number of zero points in the dominating carrier distributions, is determined by a certain sublattice and independent of k(z). For each LS, the difference between the number of zero point of the a and b sublattices is fixed and equals one. Furthermore, a reliable approximate solution of the low-lying LS energy is obtained. Through observing this solution, the dependence of the LS energy on the field strength and quantum number, k(z)-dependent energy spacing between two LSs, and the values of atomic hopping integrals are reasonably determined. A comparison of the AA-stacked graphene superlattice and monolayer graphene demonstrates that they possess some similar magneto-electronic properties.