Electronic friction
By R. David Whitby, Contributing Editor | TLT Worldwide May 2026
New research results provide well-defined insights into how electronic friction can be controlled and reduced with far greater precision.
Tribologists spend a lot of time investigating and implementing methods to try to eliminate friction and wear. Friction opposes motion, wastes energy, can cause wear and occurs whenever two surfaces slide against each other. Reducing friction requires lubricants, low friction materials and/or surface engineering.
However, it has been found that parts of devices which are perfectly smooth can still experience subtle effects that cause friction. One of these can occur at metallic or chemically active surfaces. As they slide past one another, atomic nuclei in one surface can transfer some of their energy to electrons in the other surface, exciting them to higher energy levels. The energy transfer produces a drag force that increases with sliding velocity—the effect known as “electronic friction.” Even when surfaces slide perfectly, mechanical motion can still agitate the numerous electrons within some materials.
Until now, the effect has been difficult to study because it could not be separated easily from “phononic friction,” which is a better-known mechanism generated by atomic-scale vibrations. This also dissipates the energy of moving surfaces, leading to friction and possibly wear. The first studies of electronic friction occurred in 1998, when teams studying superconductors, materials that conduct electricity perfectly at extremely low temperatures, found that electronic friction had disappeared in this special state.
A team led by Zhiping Xu at Tsinghua University, Beijing, designed an experimental setup involving a moving graphite surface sliding over a fixed bottom surface.
1 Several different materials, including metallic, semiconducting and insulating samples, were used for the lower layer.
The semiconducting layer was made from either molybdenum and sulfur or from boron and nitrogen. These, together with graphite, are good solid lubricants, which means that mechanical friction from them sliding against each other was nearly zero. This enabled the team to focus on the more subtle friction effects. By slightly rotating the atomic lattices of the two surfaces relative to each other, they exploited structural superlubricity,
1 a state in which atomic-scale vibrations are almost entirely suppressed. With phononic friction minimized, any remaining friction could be attributed primarily to electronic effects. Using this platform, the team carried out a series of experiments guided by theoretical models predicting how electronic friction should vary.
They first studied how electronic states in the semiconductor layer corresponded to how energy was lost during sliding to confirm that they were really looking at electronic friction.1 By applying a bias voltage across the device, which altered the electronic coupling and charge distribution at the interface, the researchers were able to weaken electronic friction and control it.
When they applied mechanical pressure to the top surface, they found that the electronic states in the two layers began to overlap and hybridize into a single, shared system. This reduced the electronic excitations generated during sliding, allowing them to switch off electronic friction entirely.
1
By separating the effects of electronic and phononic friction, the results provide well-defined insights into how friction can be controlled and reduced with far greater precision. With further technical developments, the approach could eventually lead to devices that enable precise, real-time control over friction in nanoscale systems.
Dr. Zhiping knows that managing all types of friction present in a device is difficult, in part, because researchers have not yet developed a mathematical model that would rigorously relate all of them to each other. However, in cases where electronic friction is the dominant cause of energy waste or wear, he believes his team’s findings could already be promising.
REFERENCE
1.
Yu, Z. et al. (2026), “On-device control of electronic friction,”
Physical Review X. Available at
https://doi.org/10.1103/jlc2-qmr1.
David Whitby is chief executive of Pathmaster Marketing Ltd. In Surrey, England. You can reach him at pathmaster.marketing@yahoo.co.uk.