Conductance Oscillations in Zigzag Platinum Chains

Abstract

Using first principles simulations we perform a detailed study of the structural, electronic and transport properties of monoatomic platinum chains, sandwiched between platinum electrodes. First, we demonstrate that the most stable atomic configuration corresponds to a zigzag arrangement that gradually straightens as the chains are stretched. Secondly, we find that the averaged conductance shows slight parity oscillations with the number n of atoms in the chain. Additionally, the conductance of chains of fixed n oscillates as the end atoms are pulled apart, due to the gradual closing and opening of conductance channels as the chain straightens. 73.40.Jn,71.15.Ap The existence of single atom chains was demonstrated some time ago using the scanning tunneling microscope (STM) and mechanically-controllable break junctions (MCBJ) [1] where a quantized conductance close to G 0 = 2 e 2 /h for gold was measured, in agreement with previous theoretical predictions [2]. Since then, a number of experiments [3,4] and theoretical calculations [5] have proved that the 5d elements Au, Ir and Pt can be used to produce monoatomic chains. For gold chains [1], the average distance between conductance peaks was found to be 2.5Å with the conductance G of the last plateau being very close to G 0 . The ensemble-averaged conductance also shows small oscillations around G 0 as the length of the chain increases [4].For platinum, the average distance between the peaks in the length-histograms is about 1.9-2.3Å [3,4]. In contrast with gold, the conductance is no longer an integer multiple of G 0 , but instead decreases from 1.6 G 0 to 1.2 G 0 as the length of the chain increases [4]. In addition, significant conductance oscillations are superimposed on top of this decreasing trend, which have been attributed to a parity effect. [4,6]. The rich behavior of platinum compared with gold arises from the larger number of conduction channels at the Fermi energy (E F ) due to the presence of d bands [7].To understand the structural, electronic and transport properties of platinum chains, we have performed a complete series of first principles simulations of platinum chains attached to platinum fcc leads. We have employed our newly developed code SMEAGOL [8,9], which calculates the density matrix and the transmission coefficients of a two probe device using the non-equilibrium Green's Function formalism (NEGF) [10]. The scattering potential is calculated self-consistently using the SIESTA implementation of density functional theory [11,12,13]. We have approximated the exchange and correlation potential by the Local Density Approximation (LDA), since we have found that provides a slightly more accurate description of the structural and conducting properties of bulk and infinite platinum chains than GGA [14]. We have not included in our calculations spin polarization which is only relevant for very stretched chains [15]. Our main result is that the most stable arrangement of platinum chains corresponds

Atomic configuration, conductance, and tensile force of platinum wires of single-atom width

“…Similar relationships were observed by Smit et al 51 using a scanning tunneling microscope and a mechanically controllable break junction technique. From first-principles simulation and density-functional theory, García-Suárez et al 39 also obtained a similar relationship. These experimental and theoretical studies result in the parity oscillation of conductance during extension of Pt ASWs.…”

“…4,6,7,13,[29][30][31][32][33][34][35][36][37] The deviation from quantized values is interpreted on the basis of inelastic scattering of electrons at 5d orbitals. 13,33,38,39 A relationship between the conductance and length of ASWs was reported; for Au, Pt, and Ir ASWs, their conductance oscillates depending on parity in the number of constituent atoms. 13,33,38,39 Furthermore, whereas the average conductance level of Au ASWs is maintained as wire length increases up to the ten-atom length, the average conductance of Pt ASWs decreases with wire length.…”

Effects of bonding type and interface geometry on coherent transport through the single-molecule magnetMn12

“…A recent study reveals that firstprinciples calculations based on DFT and NEGF provide qualitative features of transport in such a regime. 35 For example, when a Pt break junction becomes broken with vacuum between the electrodes, a first-principles calculation showed exponentially decaying conductance as a function of distance between the electrodes. 35 This result suggests that our methodology can be used to understand the transport in the case of physisorption although the physical mechanism in our case differs from that in the broken junction.…”

Electron Transport in Magnetic Quantum Point Contacts

“…4c are much more rounded with a steeper reduction as the magnetic field approaches 0 T. These effects that can change drastically from contact to contact indicate that the XMR on Pt monoatomic contacts and chains is highly dependent on the exact atomic configuration of the contact. This experimental data goes hand-in--hand with theoretical prediction that even the slightest stretching of the bonds between neighboring atoms can change the magnetic behaviour [71,74].…”

“…Nanoparticles of Pt are often used as a catalyst, for instance in catalytic converters in automobiles and in fuel cells, where the size of these nanoparticles is an important parameter [69]. A more recent development in the research of Pt has been the discovery that it is one of three metals found to form monoatomic chains, along with Au and Ir [1,[70][71][72][73]. During the last decade, theoretical investigations on such atomic-sized Pt contacts have predicted the emergence of magnetism in such small structures [74][75][76].…”