Tuning independently the Fermi energy and spin splitting in Rashba systems: ternary surface alloys on Ag(111)

Abstract

By detailed first-principles calculations we show that the Fermi energy and the Rashba splitting in disordered ternary surface alloys Bi(x)Pb(y)Sb(1 - x - y)/Ag(111) can be independently tuned by choosing the concentrations x and y of Bi and Pb, respectively. The findings are explained by three fundamental mechanisms, namely the relaxation of the adatoms, the strength of the atomic spin-orbit coupling, and band filling. By mapping the Rashba characteristics, i.e. the splitting k(R) and the Rashba energy E(R), and the Fermi energy of the surface states in the complete range of concentrations, we find that these quantities depend monotonically on x and y, with a very few exceptions. Our results suggest that we should investigate experimentally effects which rely on the Rashba spin-orbit coupling depending on spin-orbit splitting and band filling.

Unconventional transport in low-density two-dimensional Rashba systems

“…Now of course our SCFBA analysis was performed at zero temperature, but given the robustness of the non-perturbative transport effects to finite temperature in the Boltzmann treatment (Figs. 5,6), it is reasonable to assume that at least the first plateau would be observable at temperatures above the Wigner crystal melting point.…”

“…For a long time, the study of Rashba SOC was restricted to non-centrosymmetric crystals and two-dimensional (2D) quantum wells in heterostructures. It has since grown to ubiquity through advances in surface state measurement and manipulation [3][4][5][6], synthetic SOC in ultra-cold atoms [7], and the recognition that local asymmetry can produce Rashba SOC even in centrosymmetric crystals [8].…”

Strongly enhanced electron-phonon coupling in the Rashba-split state of the Bi/Ag(111) surface alloy

“…The special interest in ( (111) and several similar systems involving Cu as a substrate 22 or other heavy elements on the surface, was first caused by the strong splitting of the bands 10 but it soon became apparent that a genuine novelty lies in the design freedom arising from the possibility of combining different substrates, heavy atoms, and additional adsorbates. Indeed, it was established that both the strength of the spin-splitting and the position of the Fermi level can be tuned via alloying 23,24 or adsorption. [25][26][27] This is particularly interesting since it offers the possibility, at least in principle, to change the (spin) transport properties of the surface alloy.…”

Unconventional dc Transport in Rashba Electron Gases

“…Recently, intense research efforts [2] have been devoted to twodimensional materials with broken inversion symmetry, where the SO strength, parametrized by a characteristic energy scale E 0 , can be tuned by means of external conditions (electric fields, gating, doping, pressure, strain, etc.). In most of these systems (for example, surface alloys [3][4][5][6][7][8][9], layered bismuth tellurohalides [10][11][12][13][14][15][16], HgTe quantum wells [17], and interfaces between complex oxides [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]) the total charge carrier density n can be tuned down to very small concentrations, implying very small Fermi energies E F . Although the high-density (HD) regime E F ≳ E 0 has been widely investigated [2,[33][34][35][36][37][38], relatively less attention has been paid to the opposite regime of dominant SO (DSO), E 0 ≳ E F .…”