Dr.thedudeman

We demonstrate a canted magnetization of biatomic zigzag Co chains grown on the 5 x 1 reconstructed Ir(001) surface using density functional theory calculations and spin-polarized scanning tunneling microscopy (SP-STM) experiments. Biatomic Co chains grow in three different structural configurations and are all in a ferromagnetic state. Two chain types possess high symmetry due to two equivalent atomic strands and an easy magnetization direction which is along one of the principal crystallographic axes. The easy magnetization axis of the zigzag Co chains is canted away from the surface normal by an angle of 33 degrees. This giant effect is caused by the broken chain symmetry on the substrate in combination with the strong spin-orbit coupling of Ir. SP-STM measurements confirm stable ferromagnetic order of the zigzag chains with a canted magnetization.

We present a computational scheme for extracting the energy level alignment of a metal/molecule interface, based on constrained density functional theory and local exchange and correlation functionals. The method, applied here to benzene on Li(100), allows us to evaluate charge transfer energies, as well as the spatial distribution of the image charge induced on the metal surface. We systematically study the energies for charge transfer from the molecule to the substrate as function of the molecule-substrate distance, and investigate the effects arising from image charge confinement and local charge neutrality violation. For benzene on Li(100) we find that the image charge plane is located at about 1.8 \AA above the Li surface, and that our calculated charge transfer energies compare perfectly with those obtained with a classical electrostatic model having the image plane located at the same position. The methodology outlined here can be applied to study any metal/organic interface in the weak coupling limit at the computational cost of a total energy calculation. Most importantly, as the scheme is based on total energies and not on correcting the Kohn-Sham quasiparticle spectrum, accurate results can be obtained with local/semi-local exchange and correlation functionals. This enables a systematic approach to convergence.

We present results of Scanning Tunneling Microscopy and Spectroscopy (STS) measurements on the "Kondo insulator" SmB$_6$. The vast majority of surface areas investigated was reconstructed but, infrequently, also patches of varying size of non-reconstructed, Sm- or B-terminated surfaces were found. On the smallest patches, clear indications for the hybridization gap and inter-multiplet transitions were observed. On non-reconstructed surface areas large enough for coherent co-tunneling we were able to observe clear-cut Fano resonances. Our locally resolved STS indicated considerable finite conductance on all surfaces independent of their structure.

Author(s): Ivan V. Pechenezhskiy, Xiaoping Hong, Giang D. Nguyen, Jeremy E. P. Dahl, Robert M. K. Carlson, Feng Wang, and Michael F. Crommie

We have developed a new scanning-tunneling-microscopy–based spectroscopy technique to characterize infrared (IR) absorption of submonolayers of molecules on conducting crystals. The technique employs a scanning tunneling microscope as a precise detector to measure the expansion of a molecule-decorat...

[Phys. Rev. Lett. 111, 126101] Published Mon Sep 16, 2013

Author(s): A. Gyenis, I. K. Drozdov, S. Nadj-Perge, O. B. Jeong, J. Seo, I. Pletikosić, T. Valla, G. D. Gu, and A. Yazdani

Topological crystalline insulators represent a novel topological phase of matter in which the surface states are protected by discrete point group symmetries of the underlying lattice. Rock-salt lead-tin-selenide alloy is one possible realization of this phase, which undergoes a topological phase tr...

[Phys. Rev. B 88, 125414] Published Mon Sep 09, 2013

Author(s): Julen Ibañez-Azpiroz, Aitor Bergara, E. Ya. Sherman, and Asier Eiguren

We present a detailed analysis of the spin-flip excitations induced by a periodic time-dependent electric field in the Rashba prototype Au(111) noble metal surface. Our calculations incorporate the full spinor structure of the spin-split surface states and employ a Wannier-based scheme for the spin-...

[Phys. Rev. B 88, 125404] Published Tue Sep 03, 2013

Author(s): Bruno Schuler, Wei Liu, Alexandre Tkatchenko, Nikolaj Moll, Gerhard Meyer, Anish Mistry, David Fox, and Leo Gross

We measured the adsorption geometry of single molecules with intramolecular resolution using noncontact atomic force microscopy with functionalized tips. The lateral adsorption position was determined with atomic resolution, adsorption height differences with a precision of 3 pm, and tilts of the mo...

[Phys. Rev. Lett. 111, 106103] Published Thu Sep 05, 2013

Author(s): Q. D. Gibson, L. M. Schoop, A. P. Weber, Huiwen Ji, S. Nadj-Perge, I. K. Drozdov, H. Beidenkopf, J. T. Sadowski, A. Fedorov, A. Yazdani, T. Valla, and R. J. Cava

We describe the topological surface states of Bi₄Se₃, a compound in the infinitely adaptive Bi₂-Bi₂Se₃ natural superlattice phase series, determined by a combination of experimental and theoretical methods. Two observable cleavage surfaces, terminating at Bi or Se, are characterized by angle-resolve...

[Phys. Rev. B 88, 081108] Published Fri Aug 30, 2013

Nature Physics 9, 368 (2013). doi:10.1038/nphys2610

Authors: Manuela Garnica, Daniele Stradi, Sara Barja, Fabian Calleja, Cristina Díaz, Manuel Alcamí, Nazario Martín, Amadeo L. Vázquez de Parga, Fernando Martín & Rodolfo Miranda

We introduce time-reversal-symmetry breaking by doping Cr atoms into the topmost quintuple layer or into the bulk of Sb2Te3 thin films. We find that even at a high Cr-doping level the Landau level spectrum keeps a good quality, enabling the first demonstration of deviation of the zero-mode Landau level, induced by the acquisition of a mass term in the surface states in the presence of surface or bulk magnetic doping. The magnitude of the mass term in the surface states increases with increasing Cr-doping level. Our observation suggests Cr-doped Sb2Te3 is a promising candidate for the realization of the proposed novel magnetoelectric effects.