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The UAM PhD student Juan Hurtado presents his work on "Quantum Interference in Radical and Neutral Single-Molecule Junctions" at the APS March meeting 2022 in Chicago, USA
G00 026344 Hurtado.mp4
IBM PhD student Andrea Gemma defended his thesis "Thermal transport at the quantum scale" at University of Basel in December 2021
The Thesis can be found at https://edoc.unibas.ch/87813/
Stay of UAM PhD student Juan Hurtado at TU Delft - August-October 2021
Juan's say at TU Delft aimed at learning the 'Mechanically controllable break junction' (MCBJ) technique, capable of creating molecular junctions mechanically by creating a small enough distance between two electrodes to trap a molecule between them (Fig.1a). To do this, gold samples need to be lithographed to create a nano-junction, so that the two electrodes can be connected to measure the current between them. A piezoelectric tube is used to push the samples from below and create a controllable nanometric gap between the electrodes, so that the junctions can open and close in a controlled manner.
The molecule we measured was the Naph PCP para (Fig. 1b), a mechanosensitive molecule whose conductance oscillations can be observed by the stick-slip effect on individual breaking traces. Once the most likely conductance value of the molecule is obtained, we modulate the piezo while the molecule is in the junction, forcing an electrical response to a mechanical change. Analyzing the traces, was found that three types of conductance responses can be found, anti-phase, in-phase response to modulations and double-frequency conductance traces for each modulation (Fig. 3). These different modulation responses show the fermi energy at which the junction is located according to its transmission function, relating the double frequency traces to the depth of the transmission, the latter group of traces are the ones we are going to focus on.
Figure 1. (a) Sketch of the mechanically controlled break junction MCBJ setup. The sample is bent and consequently broken by moving the pushing rod up. (b) Naph PCP para molecule scheme.
Figure 2: Examples of distance-modulation traces. (a) Anti-phase, (b), in-phase and (c) double frequency.
IBM PhD student Andrea Gemma wins first price “Arts in Science” contest - May 2021
More information can be found at https://www.zurich.ibm.com/brnc/arts.html
TU Delft probe the "full" thermoelectric properties of a single molecule - March 2021
One of the dreams of physicists today is being able to harvest electricity back from dissipated heat. The key to this probably resides in circuits that contain single molecules. Instead of being limited to classical conductance, the thermopower can be enhanced dramatically by the properties of quantum states. But then, what quantum states offer good efficiency? What characteristics are desirable? Theory often offers contrasting predictions. Unfortunately, experiments have also not yet provided any proof, since they are notoriously difficult to set up. But now, researchers at Delft University of Technology (TU Delft) in collaboration with UC Louvain, University of Oxford, Northwestern University and Heriot-Watt University have done just that. They experimentally probed the gate and bias dependent thermoelectric properties of a single molecule for the very first time. The results have been published in Nature Nanotechnology.
Acquiring thermoelectric current through a single molecule holds the key to thermoelectric energy harvesters with unprecedented efficiency. This is only theoretically true, but until now detailed experimental testing has not been possible. Studying the thermoelectric properties of a single molecule is a daunting task and requires the possibility of accurately heating one side of a single molecule while maintaining the other. Side cold. We also need the ability to accurately measure the resulting minute thermal currents. It is only a few fA-pA in size. In addition, the tunability of experimental parameters such as the temperature bias applied to a single molecule and the control of its electrochemical potential is to fully understand the thermoelectric underlying physics of such atomic-sized objects. It is essential.
Read the full paper in Nature Nanotechnology at https://www.nature.com/articles/s41565-021-00859-7
International Conference on Molecular-Scale Charge and Thermal Transport January 27 - 31, 2020 , Engelberg (Switzerland)
More details about this event can be found in: www.msctt2020.empa.ch
Four QuIET partners give invited talks in the "Molecular Scale Thermoelectricity – Materials, Modelling and Measurements (MoST-M3)" meeting", September 3-5, 2019, Cambridge (UK)
Colin J. Lambert: Quantum-interference-enhanced thermoelectricity in single-molecule junctions
Nicolas Agrait: Enhancing the thermoelectric properties of molecular junctions
Martin R. Bryce: New molecules for single-molecule electronics in break junction devices.
Herre van der Zant: Single-molecule electronic components based on molecular design.
The review “Beyond Simple Substitution Patterns – SymmetricallyTetrasubstituted [2.2]Paracyclophanes as 3D Functional Materials” appears as front cover in EurJOC.
June 2, 2019
Stay of Rubén López Nebreda at EMPA Materials Science and Technology - April 2019
Rubén's say at EMPA aimed at building a probe consisting of a glass fiber of approximately 40 microns in diameter and several millimetres in length, provided with resistive platinum lines running along the fiber on opposite sides and connected to a gold cap on the rounded end of the fiber. The platinum lines act as resistive heaters and simultaneously as thermometers. The gold cap served as a scanning tip. This probe was mounted on a piezotube of a scanning tunneling microscope and made possible the local simultaneous measurement of electrical and thermal conductance in nanostructures in contact mode, while preserving the imaging capability of the microscope. This probe is an evolution of the conventional hot wire probe and will allow for exceptional resolution in the order of pW/K according to our simulations.
Figure 1: Sputter platinum around one Pyrex fiber and gold on the top (the directional sputtering was not so local, and the gold sprayed all over the length of the tip). The pico-second laser was used to ablate the front and the back of the tip and remove both metals
Figure 2: Glass mask sputtered with gold (40 nm) before the ablation. The two glass pieces were placed together symmetrically, and the laser cut the border continuously. Crosses were made for alignment. Sputtering gold on top of the glass slide gave a visual reference to the eye for where the slide is placed. Also, makes the glass semi-transparent so, at the time to setting up, we can illuminate with a background light and align the sandwich in an easier way
Figure 3: Mask alignment in a top view. The slits match perfectly. It´s shown the profile of the laser ablation through the glass
Ksenia Reznikova receives the award “The Emilie-Louise-Frey Prize 2018” for her master Thesis "Tailor-made molecular rods for graphene junctions"
November 30, 2018
Four QuIET partners give invited talks in the ACS National Meeting, March 18-22, 2018, New Orleans, LA, USA
Colin J. Lambert: Quantum-interference-enhanced thermoelectricity in single-molecule junctions
Nicolas Agrait: Enhancing the thermoelectric properties of molecular junctions
Martin R. Bryce: New molecules for single-molecule electronics in break junction devices.
Herre van der Zant: Single-molecule electronic components based on molecular design.