J.C. Séamus Davis wins Buckley Prize

The American Physical Society's annual Buckley Prize recognises and encourages outstanding theoretical or experimental contributions to condensed matter physics. The 2023 award has been made to Wadham's Senior Research Fellow, J.C. Séamus Davis. Some of Prof Davis's key contributions, which the Buckley Prize celebrates, are listed below.

Wadham College congratulates Prof Davis on his exceptional achievements and the highly prestigious award.

ATOMIC SCALE VISUALIZATION

Davis introduced and established advanced techniques and laboratory requirements allowing use of scanning tunnelling microscopes (STM) as a general instrument for visualizing electronic states in bulk crystalline materials[i]. His high-precision quantitative approach, and the variety of concepts he has introduced and demonstrated, created the prototype for quantum materials research by direct atomic-scale visualization. Quantum microscopes based on Davis approaches and designs have galvanized quantum materials visualization studies globally. Direct atomic scale imaging of even the most complex electronic structure in a very wide variety of material classes is now achieved worldwide, typically by using a combination of instruments, techniques and concepts that Davis has initiated.

QUASIPARTICLE INTERFERENCE IMAGING (QPI)

Scattering by impurity atoms produces oscillations in the density of electronic states nearby. By introducing Fourier analysis of energy-resolved density of states imaging and Davis demonstrated that such quasiparticle interference could be used as a new approach to determine the momentum space electronic structure (band structure) of crystalline conductors[ii],[iii]. This procedure was dubbed QUASIPARTICLE INTERFERENCE IMAGING (QPI), a technique that is now used throughout the physics world for study of correlated metals and superconductors; Kondo, Weyl and Hund metals; topological insulators/superconductors, ferromagnets, and Kondo-insulators.

ELECTRONIC LIQUID CRYSTALS

By analogy with classical liquid crystals used in screen technology, electronic liquid crystal translational and rotational symmetry have been predicted to appear in the strongly correlated metals. Davis pursued these predictions by developing new approaches and new techniques for STM visualization of electronic symmetry breaking. Using these new methods, several novel ordered states were revealed and visualized for the first time including: the density wave phase of cuprates[iv],[v],[vi], the electronic nematic phase of cuprates[vii],[viii], the famous electronic nematic phase of iron-based high temperature superconducts[ix].

QUANTM STATES OF COMPLEX SUPERCONDUCTORS

Davis has focused on developing QPI in the millikelvin temperature range near absolute zero, specifically to measure the signed[x],[xi], quantum structure of electron-pairs in the most complex and mysterious superconductors. These studies have been highly productive discovering the superconducting energy gap structure of different cuprates, iron-based superconductors[xii], heavy fermion superconductors[xiii], topological superconductors [xiv], and of orbital selective superconductors[xv].

SCANNED JOSEPHSON TUNNELING MICROSCOPY & PAIR DENSITY WAVES

Atomic-scale scanned Josephson tunneling microscopy (SJTM) images, not the conventional single-electron quasiparticles of metals, but a macroscopically quantum coherent state of electron-pairs of a superconductor. Davis developed the first functional SJTM and introduced SJTM techniques that allowed discovery the electron-pair density wave (PDW) state in cuprates[xvi]. He discovered that the PDW exhibits periodic modulations in the electron-pair density, of the single-electron response to the electron-pair crystal[xvii], and of the associated electron-pairing energy gap,[xviii]. Increasingly sophisticated SJTM techniques now reveal the atomic-scale interplay of a PDW with other ordered electronic states, such as superconductivity[xix] and charge density wave3.

Séamus Davis received his B.Sc. from University College Cork, Ireland in 1983. He received his Ph.D. from the University of California, Berkeley in 1989, under Prof. Richard E. Packard. Davis’ active research interests are in the macroscopic quantum physics of quantum matter including studies of superconductors, superfluids and supersolids; Kondo, Weyl and Hund metals; magnetic and Kondo topological condensates; spin & monopole liquids.

Davis’ active research interests are in the macroscopic quantum physics of emergent quantum matter including studies of superconductors, superfluids and supersolids; Kondo, Weyl and Hund metals; magnetic and Kondo topological condensates; spin & monopole liquids. A specialty is development of innovative instrumentation to allow direct atomic-scale visualization or perception of the macroscopic quantum phenomena that are characteristic of these states.

His honors include the Outstanding Performance Award of Berkeley National Lab., the Science and Technology Award of Brookhaven National Lab., the Fritz London Memorial Prize, the H. Kamerlingh-Onnes Memorial Prize, the Science Foundation Ireland Medal of Science, and the O.V. Lounasmaa Memorial Prize.

Davis is a Fellow of the Institute of Physics (UK), the American Physical Society (USA), the Royal Irish Academy (Ireland), the America Assoc. for Advancement of Science (USA) , and a Member of the US National Academy of Sciences (USA).

[i] S.H. Pan et al Rev. Sci. Instrum. 70, 1450 (1999) Citation[392]

[ii] J.E. Hoffman et al Science 297, 1148 (2002) [739]

[iii] K. McElroy et al Nature 422, 592 (2003) [630]

[iv] J.E. Hoffman et al Science 297 1148 (2002) [1038]

[v] T. Hanaguri et al Nature 430 , 1001 (2004) [840]

[vi] Y. Kohsaka et al Science 315, 1380 (2007) [742]

[vii] M.J. Lawler et al Nature 466, 374 (2010) [587]

[viii] A. Mesaros et al Science 333, 426 (2011) [165]

[ix] T.M. Chuang et al Science 327, 181 (2010) [575]

[x] P.O. Sprau et al Science 357, 75 (2017) [315]

[xi] R. Sharma et al Quantum Materials 6,7 (2020)

[xii] M.P. Allan et al Science 336, 563 (2012) [215]

[xiii] M.P. Allan et al Nature Physics 9, 468 (2013) [154]

[xiv] R. Sharma et al PNAS 117, 5222 (2020) [55]

[xv] K. McElroy et al Nature 422, 592 (2003) [630]

[xvi] M.H. Hamidian et al Nature 532, 343 (2016) [229]

[xvii] S.D. Edkins et al Science 364, 976 (2019) [98]

[xviii] Z. Du et al Nature 580, 6570 (2020) [36]

[xix] X. Liu et al Science 372 1447 (2021) [7]