


Forthcoming Seminars at F1
Tuesday 26 Mar 2019 10:15  Jürgen Schnack  Magnetism of free and deposited magnetic molecules 

Magnetic molecules possess many interesting properties. In this presentation I focus on some frustration effects such as an enhanced magnetocaloric effect as well as on the modification of magnetic properties in contact with nonmagnetic metallic substrates. I am also going to explain very recent developments to calculate magnetic observables for large spin systems.
Geometric spin frustration in lowdimensional magnetic materials such as the two dimensional antiferromagnetic kagome lattice can lead to unusual behavior. Some of these features are present in magnetic molecules and lead to a deeper understanding of extended systems. Among such findings are localized independent magnons, which are responsible for flat bands, giant magnetization jumps and an increased magnetocaloric effect. The latter can also be observed in molecules with the structure of a sawtooth chain. In addition, we could report about the experimental realization of adiabatic demagnetization experiments using heptametallic gadolinium molecules. In the cooling experiment 200 mK could be reached and a rich structure of the isentropes could be observed. When put on a nonmagnetic metallic surface, magnetic molecules may change their properties due to the coupling to the conduction electrons. Following an experimental realization of stacked molecules, which form short spin chains, we can show how strong such an interaction needs to be in order to screen the terminal spin completely.
Seminar room for physics (JSI main building) 
Seminars Archive
2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 5 Mar 2019 11:15  Marko Žnidarič (FMF, UL)  Localized and ballistic eigenstates in chaotic spin ladders and the FermiHubbard model 

I will introduce a ladder model with or without disorder that is in general chaotic, but that includes the integrable Hubbard chain as a special case. One can analytically show the existence of atypical eigenstates of such a model that are populated by noninteracting excitations. Depending on parameters they can e.g. exhibit Anderson localization, or, surprisingly, ballistic transport at any disorder strength. These properties differ strikingly from those of typical eigenstates nearby in energy, which give rise to diffusion. Results have implications for possible localization in the presence of nonAbelian symmetries, as well as for phases of matter that are intermediate between full ergodicity and integrability.
Seminar room for physics (JSI main building) 
26 Feb 2019 11:15  Mikhail Kiselev  LandauZener Interferometry in Multilevel Systems 

We propose universal approach to LandauZener (LZ) problem in a
multilevel system. The problem is formulated in terms of generators of
SU(N) algebra and maps the Hamiltonian onto the effective anisotropic
pseudospin (N1)/2 model. The vector Bloch equation for the density matrix
describing the temporal evolution of the multilevel crossing problem is
derived and solved analytically for two generic cases: i) threelevel
crossing problem representing a minimal model for a LZ interferometer and
ii) fourlevel crossing problem corresponding to a minimal model of
coupled interferometers. It is shown that the analytic solution of the
Bloch equation is in excellent quantitative agreement with the numerical
solution of the Schroedinger equation for the 3 and 4level crossing
problems. The solution demonstrates oscillation patterns which radically
differ from the standard patterns for the twolevel LandauZener problem:

5 Feb 2019 11:15  Tomaž Rejec  Timedependent thermoelectric transport in nanosystems: reflectionless Luttinger field approach 

Recently the Luttinger field approach was proposed as a way to simulate switching on a
temperature gradient across a nanoscale device initially in thermal equilibrium. The time
dependent particle and heat currents can then be calculated by propagating the initial equilibrium state of the system in time. Unfortunately applying a uniform Luttinger field in the
whole of a lead causes a discrepancy between steady state currents in the long time limit and
those predicted by the LandauerBüttiker formulas as well as artefacts at short times. Here
we propose a modified approach where the Luttinger field gradually reaches its final value
across a transition region. If the length of the transition region is sufficient, the electrons
move through without reflecting. In this way the correct energy distribution of electrons
originating from such a lead, corresponding to the new temperature, is established in the
scattering region. Our approach is tested on a single quantum dot and a parallel double
quantum dot system.
Seminar room for physics (JSI main building) 




22 Mar, 2019 Seminar: Mar 26: Magnetism of fr... Jürgen Schnack...  14 Mar, 2019 Abroad: Tutorial Lecture Jernej F. Kamenik...  4 Mar, 2019 Seminar: Mar 5: Localized and b... Marko Žnidarič (FMF, ...  4 Mar, 2019 Abroad: Contributed Talk Nejc Košnik...  28 Feb, 2019 Abroad: Seminar Jernej F. Kamenik...  28 Feb, 2019 Abroad: Invited Talk Jernej F. Kamenik...  25 Feb, 2019 Seminar: Feb 26: LandauZener In... Mikhail Kiselev...  11 Feb, 2019 Publication: Hackl L., Vidmar L., Ri... Phys. Rev. B 99... 

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