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TT: Fachverband Tiefe Temperaturen
TT 69: Multiferroic Oxide Thin Films and Heterostructures II (joint session KFM/TT/MA)
TT 69.6: Talk
Wednesday, March 14, 2018, 17:00–17:15, EMH 225
Local observables in inhomogenous systems — •Raffaele Resta1 and Antimo Marrazzo2 — 1IOM-CNR, Trieste, Italy — 2THEOS, EPF Lausanne, Switzerland
When addressing inhomogenous systems (e.g. heterostructures) a key issue is which physical properties do (or do not) admit a local expression. It is known since long time that spin magnetization is indeed local, and that the density of spin magnetization is well defined quantity. It is also known (since the early 1990s) that instead polarization density is an ill defined concept. Bulk electric polarization P is a Berry phase of the electronic wavefunction: as such it does not admit any local representation. In analogy with P, orbital magnetization is a geometrical property of the electronic ground state; but at variance with P, it also admits a local representation with a well defined density in coordinate space [1,2]. Here we address one further property: the insulating/metallic character of a region in an inhomogeneous system. A well known tool to investigate this property is the local density of states, but it is not a ground-state property. According to Kohn (1964) the insulating/metallic character of a material stems from a different organization of the electrons in their ground state. We define a local ``marker" which probes such organization, and we validate it by means of computer simulations.
[1] R. Bianco and R. Resta, Phys. Rev. Lett. 110, 087202 (2013)
[2] A. Marrazzo and R. Resta, Phys. Rev. Lett. 116, 137201 (2016)