Research interests: experimental condensed matter physics, x-ray scattering and x-ray spectroscopy, superconductivity, resonant soft x-ray scattering, quantum materials
The Quantum Materials Spectroscopy group, led by Professor Hawthorn, studies Quantum Materials using resonant soft x-ray scattering and x-ray absorption spectroscopy at synchrotrons such as the Canadian Light Source. We use these tools to investigate intertwinned order in Quantum Materials and shed light on the long-standing mysteries of high temperature superconductors.
PhD Physics, University of Toronto, ON, 2004
MSc Physics, University of Toronto, ON, 2000
BSc Physics, McMaster University, ON, 1999
Resonant soft x-ray scattering in cuprate superconductors
A grand challenge in condensed matter physics is to identify the fundamental limit for achieving superconductivity at elevated temperatures.Meeting this challenge promises to guide the design of materials where the superconducting transition temperature can reach room temperature, harboring a wealth of transformative technological breakthroughs. The most promising materials for high temperature superconductivity are the cuprate superconductors. These materials have been studied intensively for nearly 30 years. Yet, only recently has it been recognized that superconductivity co-exists with a competing phase of matter, charge-density wave (CDW) order, which has now been shown to be generic to all the cuprates. 1
Measurements by our group on a low disorder sample of YBCO confirmed the origin of the density wave order in CuO2 planes of the cuprates, clarified its relation to the crystal structure and elucidated the microscopic character of the CDW order as arising from a spatial modulation in the energy levels of localized electronic states.2 This latter result followed directly from our group’s previous work on stripe-ordered La-based cuprates, where a similar energy modulation was identified.3 Since then, we have extended these studies to investigate the role of atomic random disorder on CDW order in the cuprates.4We showed that disorder decreases the CDW intensity but, most unexpectedly, has no effect on the correlation length or temperature dependence of CDW order.
Our most recent and possibly most significant studies investigated the symmetry of CDW order in La2-xBaxCuO4 and YBCO 5 and electronic nematicity in cuprates6.
Development of Resonant Soft X-ray Scattering endstation at the Canadian Light Source
To drive discoveries in the spectroscopy of quantum materials, our group has endeavored sdevelop a world-class endstation for resonant elastic soft x-ray scattering at the Canadian Light Source synchrotron in Saskatoon (the REIXS beamline).7 This includes a custom 4-circle UHV diffractometer, a molecular beam epitaxy (MBE) chamber for in-situ sample growth, and a multi-technique sample analysis chamber for photoelectron spectroscopy and UHV atomic force/scanning tunnelling microscopy.
Recent publications include:
- Nematicity in stripe-ordered cuprates probed via resonant x-ray scattering. A. J. Achkar, M. Zwiebler, Christopher McMahon, F. He, R. Sutarto, Isaiah Djianto, Zhihao Hao, Michel J. P. Gingras, M. Hücker, G. D. Gu, A. Revcolevschi, H. Zhang, Y.-J. Kim, J. Geck and D. G. Hawthorn Science 351, 576 (2016)
- Orbital symmetry of charge density wave order in La1.875Ba0.125CuO4 and YBa2Cu3O6.67.A. J. Achkar, F. He, R. Sutarto, Christopher McMahon, M. Zwiebler, M. Hucker, G. D. Gu, Ruixing Liang, D. A. Bonn, W. N. Hardy, J. Geck and D. G. Hawthorn Nature Materials 15, 616 (2016).
- Impact of quenched oxygen disorder on charge density wave order in YBa2Cu3O6+x.A. J. Achkar, X. Mao, Christopher McMahon, R. Sutarto, F. He, Ruixing Liang, D. A. Bonn, W. N. Hardy and D. G. Hawthorn Phys. Rev. Lett. 113, 107002 (2014).
- Distinct charge orders in the planes and chains of ortho-III ordered YBa2Cu3O6+δ superconductors identified by resonant elastic x-ray scattering A. J. Achkar, R. Sutarto, X. Mao, F. He, A. Frano, S. Blanco-Canosa, M. Le Tacon, G. Ghiringhelli, L. Braicovich, M. Minola, M. Moretti Sala, C. Mazzoli, Ruixing Liang, D. A. Bonn, W. N. Hardy, B. Keimer, G. A. Sawatzky and D. G. Hawthorn. Phys. Rev. Lett.109, 167001 (2012).
- Bulk Sensitive X-Ray Absorption Spectroscopy Free of Self-Absorption Effects. A. J. Achkar, T. Z. Regier, H. Wadati, Y.-J. Kim, H. Zhang, D. G. Hawthorn. Phys. Rev. B 83, 081106R (2011).
Please see David Hawthorn's Google Scholar profile for a current list of his peer-reviewed articles.