Session Q37: DCMP Prize Session

David Adler Award in the Field of Materials Physics: Complexity in Correlated Electrons

Studying materials is often complicated because of the interacting nature of electrons (correlated electrons), and the proliferation of interesting phases, including magnetism (ferro and antiferro), superconductivity, ferroelectricity, topological tendencies, and others. In this presentation, I will argue that the real situation is even more complex that what is often reported in textbooks. Once reliable computational many-body techniques are used as the tool of investigation for correlated electrons, a plethora of unanticipated phases is often unveiled. This strong “complexity” – namely the appearance of novel states and patterns difficult to anticipate a priori – primarily occurs when various tendencies are in competition. Thus, I will argue that the best place to look for interesting surprises is the “intermediate coupling” regime of model Hamiltonians. When the strength of couplings -- such as the on-site Hubbard repulsion, on-site Hund coupling, spin-orbit coupling in its many forms, etc. – are comparable, and in addition, many orbitals and even the lattice are active, this is where generic “frustration” tendencies could occur and create unexpected patterns and phases. This can occur even without invoking special lattice geometries, such as triangular, or long-range couplings. My talk will start with illustrations of these concepts from my early days as a scientist, and rapidly approach more recent times where computers unveiled new unforeseen phases, including various spin block phases, spirals stabilized without long-range interactions, frustrated phases in heterostructures, and others. Static and dynamic Majoranas will also be discussed. All this vast richness of states can be realized, and the discoveries accelerate, thanks to the growing availability of computational resources as well as the development of reliable computational techniques.

    

Davisson-Germer Prize in Atomic or Surface Physics: Strain Induced Nanoscale Self-assembly and Epitaxy Promoted Topological State on Surface

In this talk, I will review some of our earlier works on elucidating stress/strain induced self-assembly of nanostructures during growth of thin films and some of our recent works on surface-based topological semimetal and topological insulator states.  I would like to dedicate this presentation to my mentors, students, postdocs, collaborators and colleagues for this recognition.

    

Brief remarks from Onsager Prize Winner Peter Hanggi': Presented by: Cynthia Reichhardt

Brief remarks from Onsager Prize Winner Peter Hanggi'

               Presented by: Cynthia Reichhardt   

Mildred Dresselhaus Prize in Nanoscience or Nanomaterials Winner: Eva AndreiAtomically thin crystals: a myriad electronic incarnations viewed through STM

The discovery of atomically thin crystals has transformed the way we think about materials. Following the discovery of the first atomically thin crystal, graphene, this family of materials has rapidly grown to include dozens of viable two-dimensional (2D) crystals, with thousands more predicted theoretically. Like an alchemist’s toolbox, the 2D structure makes it possible to alter a material’s electronic properties, without changing its chemical composition, by using alternative means such as introducing strain patterns or superposing layers with a twist between their crystal axes. In this talk I will describe highlights of this rapidly evolving field with emphasis on results obtained from scanning tunneling microscopy and spectroscopy.

    

Oliver E. Buckley Condensed Matter Physics Prize: Scanned Josephson and Andreev Tunneling Microscopy: Visualizing Electron-Pair Fluids and Density Waves

Superconductors are quantum fluids and pair density waves (PDW) are quantum crystals. Both are macroscopic quantum states of coherently condensed electron pairs. To visualize and explore these states directly at atomic scale, scanned Josephson tunneling microscopes^1-5 (SJTM) are now used. Such instruments can image both the single-electron quasiparticles and, in a different mode, the quantum condensate of electron-pairs. Moreover, these instruments can, in the Andreev quasiparticle retroreflection regime, be operated as scanned Andreev tunneling microscopes (SATM). Emerging research areas include:  visualization of PDW states in conventional spin-singlet superconductors¹; in cuprate d-wave  high-temperature superconductors using d-wave scan tips^2,3,4; and in putative spin-triplet topological superconductors⁵.  PDW studies using SJTM and SATM thus open a rich new vein of macroscopic quantum physics, with great potential for discovery.

 

References

[1] Science 372, 1447 (2021)

[2] Nature 532, 343 (2016)

[3] Science 364, 976 (2019)

[4] Nature 580, 6570 (2020)

[5] Nature (2023) arXiv:2209.10859 

    

Oliver E. Buckley Condensed Matter Physics Prize Winner: Ali Yazdani

Emergent Quantum Phenomena under the Microscope 

Advances in scanning tunneling microscopy (STM) and spectroscopic mapping on the atomic scale with the STM have transformed our perception of quantum phenomena in matter. I will describe highlights of such findings by my research group in various quantum materials, from cuprate superconductors and topological materials to novel two-dimensional crystals and their stacks. STM spectroscopic mapping has been instrumental to key discoveries of the various charge-ordered or broken symmetry states as well as elucidating the nature of superconductivity in different correlated systems. In the study of topological quantum phases and their boundary modes, spectroscopic mapping with the STM has uncovered the absence of backscattering in topological surface states, the existence of signatures of Majorana zero modes in atomic chains, and has been used to visualize topological defects in quantum Hall ferromagnets. Many of these advances are made possible by the development of high-resolution instrumentation as well as more sophisticated measurement techniques or new ways of preparation of ultra-clean samples and devices. I will describe these findings and discuss the outlook for further exploration of novel quantum phases with STM or STM-based techniques.