arXiv subjects

Jonathan Marbey

Publications and source records attributed to Jonathan Marbey.

3 recordsLinked to original sources

arXiv2025

Adding Radio Frequency Capabilities to a millikelvin Scanning Tunneling Microscope

We present a simple home made solution enabling in-situ RF reflectometry measurements with a millikelvin scanning tunneling microscope (mk-STM). The additions described below were made using RF best practices following similar detection schemes commonly employed in the quantum information science (QIS) community. Using a Niobium STM tip to form a superconductor-insulator-normal metal (SIN) tunnel junction, the evolution of coherence peaks at the SC-gap edge are carefully measured to characterize the RF losses and electron temperature. We further identify impedance matching as a crucial factor to achieve high sensitivity in the reflectometry by tuning the tip-sample capacitance as a function of approach distance. As a demonstration of this capability, we measure a 50x50 nm$^2$ area of island features that have been condensed onto the surface of a gold single crystal. Position dependent reflectometry losses allow us to image island sizes down to a total surface area of 5 nm$^2$ given our current sensitivity.

physics.ins-det↗

arXiv2021

Demonstration of electron-nuclear decoupling at a spin clock transition

The ability to design quantum systems that decouple from environmental noise sources is highly desirable for development of quantum technologies with optimal coherence. The chemical tunability of electronic states in magnetic molecules combined with advanced electron spin resonance techniques provides excellent opportunities to address this problem. Indeed, so-called clock transitions (CTs) have been shown to protect molecular spin qubits from magnetic noise, giving rise to significantly enhanced coherence. Here we conduct a spectroscopic and computational investigation of this physics, focusing on the role of the nuclear bath. Away from the CT, linear coupling to the nuclear degrees of freedom causes a modulation and decay of electronic coherence, as quantified via electron spin echo signals generated experimentally and $\textit{in silico}$. Meanwhile, the effective hyperfine interaction vanishes at the CT, resulting in electron-nuclear decoupling and an absence of quantum information leakage to the nuclear bath, providing opportunities to characterize other decoherence sources.

quant-ph↗

arXiv2018

Magic angle effects in a trigonal Mn(III)3 cluster: deconstruction of a single-molecule magnet

We present angle-dependent high-frequency EPR studies on a single-crystal of a trigonal Mn3 cluster with an unusual structure in which the local magnetic easy-axes of the constituent Mn(III) ions are tilted significantly away from the molecular C3 axis towards the magic-angle of 54.7 degrees, resulting in an almost complete cancelation of the 2nd-order axial magnetic anisotropy associated with the ferromagnetically coupled total spin ST = 6 ground state. This contrasts the situation in many related Mn3 single-molecule magnets (SMMs) that have been studied intensively in the past, for which the local MnIII anisotropy tensors are reasonably parallel, resulting in substantial barriers to magnetization relaxation (Ueff = 30 to 35 cm 1) and magnetization blocking below about 2.5 K. The suppression of the 2nd-order anisotropy in the present case results in a situation in which the zero-field splitting (ZFS) of the ST = 6 ground state is dominated by 4th- and higher-order interactions. This provides a unique opportunity to study in depth how molecular geometry influences these interactions that are responsible for quantum tunneling of magnetization in high-symmetry SMMs. Angle-dependent EPR measurements provide a full mapping of the molecular magneto-anisotropy. Meanwhile, irreducible tensor operator (ITO) methods are employed in order to obtain analytic expressions that directly relate molecular anisotropy to the microscopic physics, i.e., the ZFS tensors associated with the individual MnIII ions, their orientations, and the exchange coupling between the three spins. We find that the magic-angle tilting leads to a massive compression of the ST = 6 ground state energy level diagram and strong mixing between spin projection states. Although these characteristics are antagonistic to SMM behavior, they provide important insights into the physics of polynuclear molecular nanomagnets.

cond-mat.mtrl-sci↗