Probing resonating valence bond states in artificial quantum magnets

Abstract

Designing and characterizing the many-body behaviors of quantum materials represents a prominent challenge for understanding strongly correlated physics and quantum information processing. We constructed artificial quantum magnets on a surface by using spin-1/2 atoms in a scanning tunneling microscope (STM). These coupled spins feature strong quantum fluctuations due to antiferromagnetic exchange interactions between neighboring atoms. To characterize the resulting collective magnetic states and their energy levels, we performed electron spin resonance on individual atoms within each quantum magnet. This gives atomic-scale access to properties of the exotic quantum many-body states, such as a finite-size realization of a resonating valence bond state. The tunable atomic-scale magnetic field from the STM tip allows us to further characterize and engineer the quantum states. These results open a new avenue to designing and exploring quantum magnets at the atomic scale for applications in spintronics and quantum simulations.

Observation of fractional edge excitations in nanographene spin chains

“…4 and Supplementary Figs. [19][20][21][22][23][24] that validate our theoretical picture. Figure 3 shows dI/dV spectroscopy performed on oTSCs with N = 2-6 (Fig.…”

“…An alternative approach to achieve physical realization of spin chains relies on the ability to image and manipulate individual atoms or molecules on solid surfaces by the scanning tunneling microscope (STM). Combined with the ability of STM to measure local electronic structure 16 and magnetic excitations 17 at the atomic scale, recent years have witnessed on-demand fabrication of atomic spin chains and demonstration of complex magnetic interactions and topological phenomena therein 18 , including the realization of quantum S = 1/2 models 19,20 . However, the Haldane phase has so far not been realized using this approach, despite predictions to such effect 21 .…”

Quantum-coherent nanoscience

“…Steps in this direction have been taken, for instance, adatom spin chains realize 1D spin models 65,66 , though these can still be efficiently simulated classically using density matrix renormalization methods. Quantum simulators of Hubbard dimers and 4-site plaquettes have been fabricated using dopants 67 , spins on surfaces 68 , and quantum dots 69 , but the number of sites needs to increase to surpass simulations on classical computers.…”

Double Electron Spin Resonance of Engineered Atomic Structures on a Surface

“…Quantum control of single atoms on surfaces driven by a magnetic tip has been demonstrated through continuous-wave (7)(8)(9)(10)(11) and pulsed (12) electron spin resonance (ESR) in STM. The STM can readily assemble multi-spin quantum systems (13,14) but use of ESR to coherently control a spin that is remote from the tunnel junction has not yet been considered (15)(16)(17)(18).…”