We discuss materials science examples of quantum phenomena embedded in a macroscopic, classical world. We present simple derivations showing the effects of the external world on gammaray emission (the Mössbauer effect), X-ray absorbtion (the overlap catastrophe), and on tunneling (macroscopic quantum tunneling and the Kondo effect). We draw some experimental lessons about the role of the extern...

Based on X-ray photoelectron spectroscopy, Gd5Ge 4(010) does not show evidence of surface segregation. Scanning tunneling microscopy reveals two types of terraces which alternate laterally on the surface. From the step heights, these two surface terminations are assigned as dense, Gd-pure layers in the bulk structure. There is evidence of reconstruction on one type of terrace.

Spin tunneling in the particular case of the magnetic molecular cluster octanuclear iron(III), Fe8, is treated by an effective Hamiltonian that allows for an angle-based description of the process. The presence of an external magnetic field along the easy axis is also taken into account in this description. Analytic expressions for the energy levels and barriers are obtained from a harmonic app...

We study Zener tunneling in two-dimensional photonic lattices and derive, for the case of hexagonal symmetry, the generalized Landau-Zener-Majorana model describing resonant interaction between high-symmetry points of the photonic spectral bands. We demonstrate that this effect can be employed for the generation of Floquet-Bloch modes and verify the model by direct numerical simulations of the ...

The dependence of band-to-band tunneling in p+-Si1−xGex /n+-Si1−xGex homojunctions on Ge fraction and electric field is investigated in the range 2–3×108 V/m. Negative differential resistance (NDR) in forward bias is observed for each device with the highest peak tunneling-current density of 8.2 kA/cm2 without any postannealing step. Reverse-biased band-to-band tunneling, as relevant for tunnel...

The Josephson effect is generally described as Cooper-pair tunneling but it can also be understood in a more general context. The dc Josephson effect is the pseudo-Goldstone boson of two coupled systems with a broken continuous Abelian U 1 symmetry. Hence, an analog should exist for systems with broken continuous nonAbelian symmetries. To exhibit the generality of the phenomenon and make predic...

We review our recent studies on the Kondo effect in the tunneling phenomena through quantum dot systems. Numerical methods to calculate reliable tunneling conductance are developed. In the first place, a case in which electrons of odd number occupy the dot is studied, and experimental results are analyzed based on the calculated result. Tunneling anomaly in the even-number-electron occupation c...