My Expertise
My expertise is in non-equilibrium phenomena in condensed matter physics, where I have worked on systems spanning 0D, 1D, 2D, and 3D.
Most recently I have devoted the bulk of my attention to the fascinating field of orbitronics, the transport and generation of orbital angular momentum in solids. Our group demonstrated that the conventional evaluation of the orbital Hall effect has been incorrect and differs by orders of magnitude from the correct value, while the orbital Hall effect is in many cases dominated by disorder, where we introduced a theoretical framework for treating disorder and topological contributions on the same footing. We also showed that intrinsic mechanisms lead to the orbital angular momentum not being conserved.
I have spent a considerable part of my career on spin transport and the spin-Hall effect, as well as spin generation via the Edelstein effect, and related spin-orbit torques in magnetic structures. I was a part of the Texas collaboration that contributed to the discovery of the spin-Hall effect and introduced the notion of a conserved spin current, and our group at UNSW subsequently developed a computational method to evaluate this for an arbitrary crystal.
I have worked on quantum transport theory, in particular the theory of the anomalous Hall effect in systems with strong spin-orbit interactions, and its various intrinsic and extrinsic contributions, related to topological band structure mechanisms and impurity scattering respectively. Much of my research in this area has focussed on the role of the Berry curvature in non-equilibrium situations, and its application to topological materials such as topological insulators and Weyl semimetals, as well as electron systems with non-trivial topologies in general, for example the electron gas in semiconductors and semimetals with spin-orbit interactions. Our group demonstrated that the topological contribution to the anomalous Hall effect can be identified experimentally in inevitable presence of disorder and, in a related series of works, explained magnetic phase transitions driven by topology in experiments on anomalous Hall transport and showed that textbook results on the Hall coefficient need to be revised in light of the strong contribution of spin-orbit coupling to the ordinary Hall effect. We explained experimental observations on edge state transport, and showed that a topological transistor using edge states can overcome Boltzmann's tyranny.
Our group has made significant contributions to the theory of non-linear electromagnetic responses, including the theoretical discovery of the resonant photovoltaic effect, resonant second harmonic generation, and the non-linear valley-Hall effect induced by a non-equilbrium orbital magnetic moment, the latter two in collaboration with scientists at IIT. We determined the fundamental limits of photovoltaic effects in energy conversion for practical applications, and demonstrated the existence of non-linear responses in topological 1D systems. The theoretical blueprint introduced in those works was shown to explain experiments on the non-linear Hall effect in topological materials.
An area that I continue to be interested in is quantum computing with with spin systems, in which our group has made substantial contribution to the study of electron dipole spin resonance, spin relaxation and dephasing, as well as the understanding of valley physics in Si spin qubits. Most of my recent interest in quantum computing is in spin-3/2 hole systems in semiconductors, whose spin dynamics is considerably more complicated than in conventional spin-1/2 electron systems. In these systems our group predicted the existence of coherence sweet spots, which were subsequently observed experimentally, as well as demonstrating the strong effect of inhomogeneity and disorder on qubit dynamics.
Biography
Dimi Culcer obtained his undergraduate degree and MPhys from Oxford University in 2000, and his PhD from the University of Texas at Austin in 2005. He worked as a postdoctoral research fellow first at Argonne National Laboratory between 2006-2008, and subsequently at the University of Maryland, College Park, 2008-2010. He became a faculty member at the University of Science and Technology of China in Hefei in 2010, where he was a member of the...view more
Dimi Culcer obtained his undergraduate degree and MPhys from Oxford University in 2000, and his PhD from the University of Texas at Austin in 2005. He worked as a postdoctoral research fellow first at Argonne National Laboratory between 2006-2008, and subsequently at the University of Maryland, College Park, 2008-2010. He became a faculty member at the University of Science and Technology of China in Hefei in 2010, where he was a member of the International Center for Quantum Design of Functional Materials. In 2013 he moved to UNSW and he has been here ever since.
My Awards
Future Fellowship (2019).
My Research Activities
Orbitronics
Orbitronics is a newly developed field of physics concerned with the orbital angular momentum and orbital magnetic moment of Bloch electrons in solids. Our understanding of this form of angular momentum was a significant latecomer in condensed matter physics, with the full theory for the equilibrium picture only taking shape by approximately 2010. It has revealed that orbital angular momentum of electrons in solids is strongly connected to the topological properties of the electron wave functions, such as the Berry connection and Berry curvature, while the dynamics is associated with motion within the unit cell. The orbital angular momentum has some spectacular manifestations, including substantial contributions to the electron g-factor, which can overwhelm the contribution from the spin. At the same time our understanding of this orbital angular momentum is limited: we only know what it looks like in equilibrium in a clean system, while its generation and transport by external fields is only now being investigated, and we do not understand how it is influenced by disorder and boundaries. These topics are studied extensively in our group, and we have made substantial contributions to the understanding of non-equilibrium orbital angular momentum dynamics - we demonstrated that the way the orbital current had been calculated was incomplete, that the corrections sometimes overwhelm the original value, that disorder affects the final results dramatically, that orbital transport can be extremely strong even in spin-orbit coupled systems and can in fact overwhelm spin transport, and that the orbital current calculated according to the modern theory can be nonzero even in spherically symmetric systems. Our group has related the orbital angular momentum to a form of inter-band dynamics known as Zitterbewegung, has shown that in non-equilibrium systems it is associated with the establishment of a steady-state dipole, and that strong orbital angular momentum densities can be generated in spin-3/2 hole quantum wells. These findings, and our ongoing projects in this direction, are extremely relevant to experiments and to the development of devices, since virtually all the modern interest in the orbital angular momentum is connected to its non-equilibrium properties, which lead to the orbital torque used in spintronic devices to engineer magnetisation dynamics.
Topological quantum matter
In recent years a large number of physical phenomena have been ascribed to topological mechanisms, in which the curvature of the eigenspace of the system plays a vital role in determining the robust quantisation of response functions. These phenomena are so widespread nowadays that the 2016 Nobel Prize was awarded to three scientists who revealed their topological nature. The research projects will focus on establishing the role of topological terms in the response functions of a series of newly discovered materials, including topological insulators, Weyl semimetals, and transition metal dichalcogenides.
Quantum computing
Quantum computation focuses on using quantum bits to encode information. Unlike classical bits, which can be either 0 or 1, quantum bits exploit the superposition principle and can be in any combination of 0 and 1, which can make computation considerably faster and open new avenues that are inaccessible with classical bits. The two key problems facing the community at present are increasing the lifetimes of quantum bits (coherence), which determines how long quantum information can be stored, and devising ways to couple two or more bits so that complex operations can be performed in practice (entanglement). My research projects will focus on these two phenomena, devising novel strategies to beat decoherence mechanisms and to control interactions between quantum bits, with a focus on spin-3/2 hole qubits in semiconductors.
Location
Publications
ORCID as entered in ROS
https://orcid.org/0000-0002-2342-0396