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Main speakers: Andrea Gauzzi (Univ. Pierre and Marie Curie, Paris), Vadim Cheianov (Leiden University), Erik van der Wurff (Utrecht University). Location: Utrecht, BBG 7.12.

Event details of Quantum and Topological Matter Meeting
Date 2 December 2016
Time 13:00 -18:00
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This event is part of a regular series of meetings on Quantum and Topological Matter, sponsored by Delta ITP. The objective is to bring together the theoretical physics communities in Amsterdam, Leiden and Utrecht. We encourage researchers from different areas in theoretical physics to participate!

Programme 

13:00  Welcome coffee

13:30 Andrea Gauzzi (Univ. Pierre and Marie Curie, Paris)

Rashba coupling amplification in non-symmorphic 2D crystals: a path for tuning the intrinsic spin Hall effect

14:30 Vadim Cheianov (Leiden University)

Adiabatic processes in many-body systems and the orthogonality catastrophe

15:30  Coffee break

16:00  Erik van der Wurff (Utrecht University)

Anomalous magnetic moment and chiral magnetic effect in three-dimensional semimetals

17:00 Drinks and snacks

Abstracts

Andrea Gauzzi (Universite Pierre and Marie Curie, Paris)

Rashba coupling amplification in non-symmorphic 2D crystals: a path for tuning the intrinsic spin Hall effect

Relativistic effects in solids have attracted an increasing interest as they can induce non-trivial topological phases, such as spin-polarized electronic states, with promise for spintronics applications. One example is the splitting of bands with opposite spin chirality produced by the Rashba spin-orbit coupling in asymmetric potentials. Sizable splittings have been hitherto obtained using either heavy elements, where this coupling is intrinsically strong, or large surface electric fields. Here we report experimental evidence of very large splittings up to 0.15 eV in centrosymmetric BaNiS2. This unexpected result in the absence of electronically active heavy elements is explained by a huge staggered crystal field of the non-symmorphic structure, which breaks inversion symmetry at the Ni site. We show that this mechanism of Rashba coupling amplification opens the possibility of tuning the intrinsic spin Hall effect, which would be promising for the development of spin-current devices.

Vadim Cheianov (Leiden University)

Adiabatic processes in many-body systems and the orthogonality catastrophe

The adiabatic theorem is a fundamental result established in the early days of quantum mechanics, which states that a system can be kept arbitrarily close to the instantaneous ground state of its Hamiltonian if the latter varies in time slowly enough. The theorem has an impressive record of applications ranging from foundations of quantum field theory to computational recipes in molecular dynamics. In light of this success it is remarkable that a practicable quantitative understanding of what "slowly enough" means is limited to a modest set of systems mostly having a small Hilbert space.

I will discuss how this gap can be bridged for a broad natural class of physical systems, namely many-body systems where a small move in the parameter space induces an orthogonality catastrophe. In this class, the conditions for adiabaticity are derived from the scaling properties of the parameter dependent ground state without a reference to the excitation spectrum. This finding constitutes a major simplification of a complex problem, which otherwise requires solving non-autonomous time evolution in a large Hilbert space. I will illustrate our general results on two examples motivated by recent experiments.

Erik van der Wurff (Utrecht University)

Anomalous magnetic moment and chiral magnetic effect in three-dimensional semimetals

We investigate the effect of Coulomb interactions on the electromagnetic response of three-dimensional Dirac and Weyl semimetals [1]. In a calculation reminiscent of Schwinger's seminal work on quantum electrodynamics, we calculate the anomalous magnetic moment of the relativisticlike quasiparticles in a semimetal. In the case of nonzero doping, the anomalous magnetic moment is finite at long wavelengths and typically orders of magnitude larger than Schwinger's result. Next, we determine the chiral magnetic effect in a three-dimensional Weyl semimetal without inversion symmetry [2]. We elucidate some of the controversies surrounding the precise magnitude of the chiral magnetic effect.

[1] E.C.I. van der Wurff & H.T.C. Stoof, Phys. Rev. B 94, 155118 (2016).
[2] E.C.I. van der Wurff & H.T.C. Stoof, to be submitted.

Location

Buys Ballot Building (BBG), room 7.12
Princetonplein 5, Utrecht
Location on GoogleMap

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Buys Ballot Gebouw

Organisers

Cristiane Morais Smith (Utrecht)

Vadim Cheianov (Leiden)

Vladimir Gritsev (Amsterdam)

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