Implementation of SNS thermometers into molecular devices for cryogenic thermoelectric experiments

Thermocurrent flowing through a single-molecule device contains valuable information about the quantum properties of the molecular structure and, in particular, on its electronic and phononic excitation spectra and entropy. Furthermore, accessing the thermoelectric heat-to-charge conversion efficiency experimentally can help to select...

Thermoelectricity in single-molecule devices

As the miniaturization of electronics continuously progresses, harvesting and generating thermoelectric energy with high efficiency become a key concept to integrate. Theoretical studies suggest that single-molecule devices are ideal candidates for thermoelectric devices with unprecedentedly high efficiencies. Such advantage is achieved by...

Magnetic-Field Universality of the Kondo Effect Revealed by Thermocurrent Spectroscopy

Probing the universal low-temperature magnetic-field scaling of Kondo-correlated quantum dots via electrical conductance has proved to be experimentally challenging. Here, we show how to probe this in nonlinear thermocurrent spectroscopy applied to a molecular quantum dot in the Kondo regime. Our results demonstrate that the bias-dependent...

Controlling the Entropy of a Single-Molecule Junction

Single molecules are nanoscale thermodynamic systems with few degrees of freedom. Thus, the knowledge of their entropy can reveal the presence of microscopic electron transfer dynamics that are difficult to observe otherwise. Here, we apply thermocurrent spectroscopy to directly measure the entropy of a single free radical molecule in a...

Complete mapping of the thermoelectric properties of a single molecule

Theoretical studies suggest that mastering the thermocurrent through single molecules can lead to thermoelectric energy harvesters with unprecedentedly high efficiencies.^1–6 This can be achieved by engineering molecule length,⁷ optimizing the tunnel coupling strength of molecules via chemical anchor groups⁸ or...

Single-Material Graphene Thermocouples

On-chip temperature sensing on a micro- to nanometer scale is becoming more desirable as the complexity of nanodevices keeps increasing and their downscaling continues. The continuation of this trend makes thermal probing and management more and more challenging. This highlights the need for scalable and reliable temperature sensors, which...

Tunneling spectroscopy of localized states of WS2 barriers in vertical van der Waals heterostructures

In transition metal dichalcogenides, defects have been found to play an important role, affecting doping, spin-valley relaxation dynamics, and assisting in proximity effects of spin-orbit coupling. Here we study localized states in WS2 and how they affect tunneling through van der Waals heterostructures of h-BN/graphene/ WS2/metal. The...

A Mechanically Tunable Quantum Dot in a Graphene Break Junction

Graphene quantum dots (QDs) are intensively studied as platforms for the next generation of quantum electronic devices. Fine tuning of the transport properties in monolayer graphene QDs, in particular with respect to the independent modulation of the tunnel barrier transparencies, remains challenging and is typically addressed using...

Single-molecule quantum-transport phenomena in break junctions

Single-molecule junctions — devices in which a single molecule is electrically connected by two electrodes — enable the study of a broad range of quantum-transport phenomena even at room temperature. These quantum features are related to molecular orbital and spin degrees of freedom and are characterized by various energy scales that can be...

Ground-state spin blockade in a single-molecule junction

It is known that the quantum mechanical ground state of a nanoscale junction has a significant impact on its electrical transport properties. This becomes particularly important in transistors consisting of a single molecule. Because of strong electron-electron interactions and the possibility of accessing ground states with high spins, these...

Efficient heating of single-molecule junctions for thermoelectric studies at cryogenic temperatures

The energy dependent thermoelectric response of a single molecule contains valuable information about its transmission function and its excited states. However, measuring it requires devices that can efficiently heat up one side of the molecule while being able to tune its electrochemical potential over a wide energy range. Furthermore, to...

Massively parallel fabrication of crack-defined gold break junctions featuring sub-3 nm gaps for molecular devices

Break junctions provide tip-shaped contact electrodes that are fundamental components of nano and molecular electronics. However, the fabrication of break junctions remains notoriously time-consuming and difficult to parallelize. Here we demonstrate true parallel fabrication of gold break junctions featuring sub-3 nm gaps on the wafer-scale,...

Mechanically controlled quantum interference in graphene break junctions

The ability to detect and distinguish quantum interference signatures is important for both fundamental research and for the realization of devices such as electron resonators¹, interferometers² and interference-based spin filters³. Consistent with the principles of subwavelength optics, the wave nature of...