Scanning tunneling spectroscopy of magnetic bulk impurities: From a single Kondo atom towards a coupled system

Prüser, Henning

dc.contributor.advisor	Ulbrich, Rainer G. Prof. Dr.	de
dc.contributor.author	Prüser, Henning	de
dc.date.accessioned	2013-03-06T10:29:37Z	de
dc.date.available	2013-09-01T22:50:05Z
dc.date.issued	2013-03-06	de
dc.identifier.uri	http://hdl.handle.net/11858/00-1735-0000-000E-0B5C-8	de
dc.identifier.uri	http://dx.doi.org/10.53846/goediss-3762
dc.language.iso	eng	de
dc.rights.uri	http://creativecommons.org/licenses/by-nc-nd/3.0/
dc.subject.ddc	530	de
dc.title	Scanning tunneling spectroscopy of magnetic bulk impurities: From a single Kondo atom towards a coupled system	de
dc.type	doctoralThesis	de
dc.contributor.referee	Ulbrich, Rainer G. Prof. Dr.	de
dc.date.examination	2013-02-22	de
dc.subject.gok	Physik (PPN621336750)	de
dc.description.abstracteng	This thesis focuses on single impurity Kondo physics and the transition towards coupled Kondo systems in real space. Single magnetic iron and cobalt and non magnetic silver atoms embedded below a copper surface are investigated using low temperature scanning tunneling microscopy and spectroscopy. Spectroscopic information is used to map the conduction electrons at the surface in the vicinity of sub-surface impurities. Iron and cobalt atoms show a spatially extended Kondo signature which allows determining the phase shift caused by the Kondo effect. Both impurity species show similar behavior on completely different energy scales which can be understood by their different Kondo temperatures. A detailed analysis of the spectroscopic information as function of lateral tip position and impurity distance below the surface is presented for both magnetic impurity atoms. The Kondo signature shows an oscillatory behavior as function of distance, which is anisotropic for different directions. This observation is in good agreement with the band structure of the underlying copper crystal. Silver atoms are studied as a non magnetic reference system proving that the signatures are related to the localized magnetic moment of iron and cobalt. Apart from isolated single impurities, geometries where two iron impurities are located in the same monolayer close to each other are investigated. The dimer configurations show a considerably different spectral signature as compared to single iron impurities located in the same monolayer. In particular, the resonance width is strongly altered or even suppressed due to the presence of the second impurity. The experimental findings can be related to the two impurity Kondo model comprising two competing effects: On the one hand the Kondo effect, which tries to screen the impurity spin. On the other hand the Rudermann Kittel Kasuya Yosida (RKKY) interaction promoting a strong correlation between the magnetic moments of the two impurities. The behavior strongly depends on the atomic configuration of the iron dimer and not simply on the geometric distance. The strongest broadening does not occur for the smallest interatomic distance but for an intermediate separation, indicating an oscillatory behavior of the interaction strength. The experimental findings are compared with first principles calculations showing very good agreement for both strength and directionality of the magnetic interaction.	de
dc.contributor.coReferee	Pruschke, Thomas Prof. Dr.	de
dc.contributor.thirdReferee	Berndt, Richard Prof. Dr.	de
dc.subject.eng	Scanning tunneling microscopy and spectroscopy	de
dc.subject.eng	low temperature	de
dc.subject.eng	STM	de
dc.subject.eng	STS	de
dc.subject.eng	Kondo effect	de
dc.subject.eng	RKKY interaction	de
dc.subject.eng	Friedel oscillation	de
dc.subject.eng	sub-surface impurities	de
dc.subject.eng	single-impurity Kondo physics	de
dc.subject.eng	two-impurity Kondo physics	de
dc.identifier.urn	urn:nbn:de:gbv:7-11858/00-1735-0000-000E-0B5C-8-1	de
dc.affiliation.institute	Fakultät für Physik	de
dc.description.embargoed	2013-09-01	de
dc.identifier.ppn	773355227

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