Quantum phase transitions in anisotropic and frustrated systems

Datum

30.09.2015

Zeit

14:00 - 15:00

Sprecher

Prof. Dr. Sebastian Eggert

Zugehörigkeit

Department of Physics, University of Kaiserslautern

Sprache

en

Hauptthema

Materialien

Andere Themen

Materialien, Physik

Host

Christine Malbrich

Beschreibung

Abstract The emergence of new properties from low-dimensional building blocks is a universal theme in different areas in physics. The investigation of transitions between isolated and coupled low-dimensional systems promises to reveal new phenomena and exotic phases. In this talk we will consider two prototypical systems which show quantum phase transitions between a low dimensional phase and higher dimensional behavior. Interacting 1D bosons which are coupled in a two-dimensional array are maybe the most fundamental example of a system which illustrates the concept of a dimensional phase transition. However, recent experiments using ultracold gases have shown a surprising discrepancy between theory and experiment [1] and it is far from obvious if the powerlaws from the underlying 1D theory can predict the transition temperature and order parameter correctly for all interaction strength. A second system which has recently been debated in the literature is the $J-J'$ Heisenberg antiferromagnet on the triangular lattice. By tuning the ratio of $J/J'$, both the dimensionality and the frustration are changed at the same time and it is still unclear if this system may have a spin-liquid phase or incommensurate order. By using large scale numerical simulations (2D DMRG and 3D quantum Monte Carlo) we are able to study the phase transitions in great detail. For the frustrated systems a simple analytical description of the phase transition can be obtained in terms of topological string excitations. This leads to an incommensutrate phase, but the excitations become unstable in a narrow region, which allow for a possible spin liquid phase. [1] A. Vogler, R. Labouvie, G. Barontini, S. Eggert, V. Guarrera, and H. Ott Dimensional phase transition from an array of 1D Luttinger liquids to a 3D Bose-Einstein condensate, Phys. Rev. Lett. 113, 215301 (2014)

Links

• Seminars at the IFW

Letztmalig verändert: 30.09.2015, 10:01:10