Atomic-scale observation of structural and electronic orders in the layered compound α-RuCl3

Abstract

A pseudospin-1/2 Mott phase on a honeycomb lattice is proposed to host the celebrated two-dimensional Kitaev model which has an elusive quantum spin liquid ground state, and fascinating physics relevant to the development of future templates towards topological quantum bits. Here we report a comprehensive, atomically resolved real-space study by scanning transmission electron and scanning tunnelling microscopies on a novel layered material displaying Kitaev physics, α-RuCl3. Our local crystallography analysis reveals considerable variations in the geometry of the ligand sublattice in thin films of α-RuCl3 that opens a way to realization of a spatially inhomogeneous magnetic ground state at the nanometre length scale. Using scanning tunnelling techniques, we observe the electronic energy gap of ≈0.25 eV and intra-unit cell symmetry breaking of charge distribution in individual α-RuCl3 surface layer. The corresponding charge-ordered pattern has a fine structure associated with two different types of charge disproportionation at Cl-terminated surface.

Strain effects on electronic and magnetic properties of the monolayer α-RuCl3: A first-principles and Monte Carlo study

“…Recently, ultra-thin film of RulC 3 has been obtained and its bandgap value has been observed as 0:25 eV using scanning tunneling techniques. 51 There is an increment on bandgap values of ML-α-RuCl 3 in comparison to this ultra-thin film. This reduction in the bandgap value can be explained by the relation of ΔE g h 2 =(2ma 2 ), where a is the thickness of the layer and m is the effective carrier mass.…”

Electronic and magnetic properties of monolayer α-RuCl3: a first-principles and Monte Carlo study

“…Before studying the monolayer form of α-RuCl 3 , we first tested the possibility of exfoliation process to obtain monolayer from its bulk form. First, we created bulk α-RuCl 3 with a=5.99, b=10.37 and c=6.05Å lattice constants as illustrated in Figure 1 (suitable with literature 47,48,61 ) and we implemented a fracture in the bulk after four periodic layer and we systematically increase this fracture distance, at the end we calculate the corresponding cleavage energy (CE) (Figure 1). This method is very effective and has been widely confirmed.…”

Field-induced quantum criticality in the Kitaev system α−RuCl3

“…We relate the data to theoretical calculations based on a J 1 -K 1 -1 -J 3 honeycomb model. Mott insulator with a layered structure of edge-sharing RuCl 6 octahedra arranged in a honeycomb lattice [1][2][3][4][5][6][7][8]. It has been suggested [9,10] that strongly spin-orbit-coupled Mott insulators with that lattice geometry realize bond-dependent magnetic "compass" interactions [11], which, if dominant, would lead to a quantum spin-liquid (QSL) ground state as discussed by Kitaev [12].…”