Tuning the spin signal from a highly symmetric unpolarized electronic state

Abstract

A remarkably large spin signal is observed on nonmagnetic W(110) for a highly symmetric unoccupied state with no intrinsic spin polarization. The magnitude and, more importantly, the sign of this spin signal, measured by spin-and angle-resolved inverse photoemission for normal electron incidence, can be tuned in a user-defined manner by variation of the photon-detection angle and/or by rotating the spin-polarization direction of the incident electrons. Using calculations of the orbitally decomposed spectral densities, this effect is traced back to a mixing of different symmetries within the respective state. This explanation is underlined by the behavior of a second electronic state of pure symmetry, which does not show such a spin signal. In general, the spin signals of electronic states are not only influenced by their intrinsic spin polarization but also by the choice of symmetry-breaking experimental parameters in combination with the particular orbital characters of the states under investigation. The latter permits one to tune the spin signal in magnitude and sign.

Rashba-Dirac cones at the tungsten surface: Insights from a tight-binding model and thin film subband structure

“…The degree of quantitative agreement between the above results for the Rashba-Dirac surface states and both experiments and ab initio calculations for macroscopic tungsten crystals [13][14][15][16][17][18][19][20][21][22][23] is quite remarkable since all of the parameters of the tight binding model (described in Section II) have been fitted only to the electronic band structure [41][42][43] of bulk bcc tungsten. The only information about the tungsten surface that has been used as input in the present work is structural, namely, the experimentally measured relaxation distance 44,45 of surface atomic layer towards the bulk.…”

“…33 Following the recent experimental observation at the tungsten (110) surface of Rashba-like spin-split and spin-polarized electronic states forming an anisotropic Dirac cone-like band structure, 13 there has been renewed interest in developing a better understanding of this system. [13][14][15][16][17][18][19][20][21][22][23] It has been demonstrated 14 that the experimentally observed anisotropic Dirac cone-like band structure can be fitted accurately by a phenomenological third order Rashba model for surfaces with C 2v symmetry. 34 Ab initio calculations 15,17,19,20,22,23 have also accounted for the experimental data, including the Dirac conelike dispersion and the spin polarizations of the observed surface states.…”

“…[13][14][15][16][17][18][19][20][21][22][23] It has been demonstrated 14 that the experimentally observed anisotropic Dirac cone-like band structure can be fitted accurately by a phenomenological third order Rashba model for surfaces with C 2v symmetry. 34 Ab initio calculations 15,17,19,20,22,23 have also accounted for the experimental data, including the Dirac conelike dispersion and the spin polarizations of the observed surface states. However, it is also of interest to investigate the underlying physics with the help of a tight-binding model that, unlike the anisotropic Rashba phenomenology, 14 is atomistic and also can provide insights that are complimentary to those obtained from ab initio calculations.…”

“…3,4 The resulting locking of spin to the crystal-momentum offers potential avenues for the realization of novel spintronic devices and quantum computation. Electronic states that are spin-split due to strong spin-orbit coupling also occur at the surfaces of some non-magnetic metals, including gold, [5][6][7][8][9] tungsten, [10][11][12][13][14][15][16][17][18][19][20][21][22][23] silver, 6,9 copper, 24,25 bismuth, [26][27][28][29][30][31] antimony, 32 and iridium. 33 Following the recent experimental observation at the tungsten (110) surface of Rashba-like spin-split and spin-polarized electronic states forming an anisotropic Dirac cone-like band structure, 13 there has been renewed interest in developing a better understanding of this system.…”

“…However, it is also of interest to investigate the underlying physics with the help of a tight-binding model that, unlike the anisotropic Rashba phenomenology, 14 is atomistic and also can provide insights that are complimentary to those obtained from ab initio calculations. 15,17,19,20,22,23 Such a tightbinding model is introduced here and applied to tungsten thin films with (110) surfaces and their electronic subband structure.…”