Advanced search options

Advanced Search Options 🞨

Browse by author name (“Author name starts with…”).

Find ETDs with:

in
/  
in
/  
in
/  
in

Written in Published in Earliest date Latest date

Sorted by

Results per page:

Sorted by: relevance · author · university · dateNew search

You searched for subject:(Mobile impurity). Showing records 1 – 2 of 2 total matches.

Search Limiters

Last 2 Years | English Only

No search limiters apply to these results.

▼ Search Limiters

1. Silveira, Hudson Pimenta. Dinâmica de Kondo em ferromagnetos itinerantes unidimensionais.

Degree: Mestrado, Física Básica, 2013, University of São Paulo

Ferromagnetismo itinerante permanece um problema elusivo em Física. O fenômeno resulta da competição entre interação eletrônica e efeitos de muitos corpos e não pode ser tratado perturbativamente. Particularmente em uma dimensão, teoremas proíbem fases ferromagnéticas em T = 0 para modelos de rede com hopping de primeiros vizinhos. Nos últimos vinte anos, entretanto, apareceram modelos na literatura que estendem o hopping para além de primeiros vizinhos e para os quais ordem ferromagnética foi rigorosamente estabelecida. Praticamente todas as demonstrações da existência de ferromagnetos unidimensionais são feitas em fase isolante (com exceção de casos patológicos, como repulsão infinita). Isto nos levou a investigar o acoplamento entre os setores de spin e carga no regime fortemente interagente quando se dopa o sistema, o que introduz pontos de Fermi pF e -pF. Encontramos, com teoria de perturbação, singularidades logarítmicas na autoenergia do mágnon quando seu momentum é pF ou -pF. Derivamos uma teoria de campo efetiva para o espalhamento em torno desses pontos entre os mágnons e férmions sem spin (que representam o setor de carga). O modelo efetivo é similar ao modelo Kondo, que consiste de uma impureza magnética localizada acoplada localmente com um mar fermiônico por uma interação de troca entre spins. Em nosso modelo, há, na realidade, um pseudospin que indica se o momentum de uma partícula é próximo de pF ou de -pF e o mágnon se comporta como uma impureza móvel. A mobilidade da impureza leva a uma relação de dispersão para os férmions dependente do pseudospin da impureza.

Itinerant ferromagnetism remains an elusive problem in Physics. The phenomenon arises from a competition between electronic interaction and many-body effects and cannot be treated perturbatively. Particularly in 1D, there are rigorous proofs that forbid ferromagnetic phase for lattice models with nearest-neighbours hopping only. In the last twenty years, however, models with hopping beyond nearest-neighbours were proposed in the literature and for which ferromagnetic phase was rigorously established. Virtually every proof of the existence of one-dimensional ferromagnets is done in an insulator phase (disregarding some pathological cases, such as infinite electronic repulsion). That motivated us to investigate the coupling between spin and charge sectors in the strongly interacting regime when we dope the system, introducing two Fermi points, pF and -pF. We found out, through perturbation theory, logarithmic singularities in the magnon selfenergy when its momentum is pF or -pF. To understand them, we derived an effective field theory for the scattering between magnons and spinless fermions (which represent the charge sector) close to these points. The effective model resembles the Kondo model, which describes a magnetic impurity locally coupled to a fermionic sea through spin exchange interaction. In our model, there is actually a pseudospin that indicates if a particle momentum is closest to pF or -pF and the magnon behaves as a mobile…

Advisors/Committee Members: Pereira, Rodrigo Gonçalves.

Subjects/Keywords: Efeito Kondo; Ferromagnetism; Ferromagnetismo; Impureza móvel; Kondo effect; Mobile impurity; One-dimensional systems; Sistemas unidimensionais

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Silveira, H. P. (2013). Dinâmica de Kondo em ferromagnetos itinerantes unidimensionais. (Masters Thesis). University of São Paulo. Retrieved from http://www.teses.usp.br/teses/disponiveis/76/76131/tde-18092013-084836/ ;

Chicago Manual of Style (16th Edition):

Silveira, Hudson Pimenta. “Dinâmica de Kondo em ferromagnetos itinerantes unidimensionais.” 2013. Masters Thesis, University of São Paulo. Accessed November 14, 2019. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-18092013-084836/ ;.

MLA Handbook (7th Edition):

Silveira, Hudson Pimenta. “Dinâmica de Kondo em ferromagnetos itinerantes unidimensionais.” 2013. Web. 14 Nov 2019.

Vancouver:

Silveira HP. Dinâmica de Kondo em ferromagnetos itinerantes unidimensionais. [Internet] [Masters thesis]. University of São Paulo; 2013. [cited 2019 Nov 14]. Available from: http://www.teses.usp.br/teses/disponiveis/76/76131/tde-18092013-084836/ ;.

Council of Science Editors:

Silveira HP. Dinâmica de Kondo em ferromagnetos itinerantes unidimensionais. [Masters Thesis]. University of São Paulo; 2013. Available from: http://www.teses.usp.br/teses/disponiveis/76/76131/tde-18092013-084836/ ;


University of Minnesota

2. Schecter, Michael. Dynamics of mobile impurities in one-dimensional quantum liquids.

Degree: PhD, Physics, 2014, University of Minnesota

We study the dynamics of mobile impurities in a one-dimensional quantum liquid. Due to singular scattering with low-energy excitations of the host liquid, the impurity spectral properties become strongly renormalized even at weak coupling. This leads to universal phenomena with no higher-dimensional counterparts, such as lattice-free Bloch oscillations, power-law threshold behavior in the impurity spectral function and a quantum phase transition as the impurity mass exceeds a critical value. The additional possibility of integrability in one-dimension leads to the absence of thermal viscosity at special points in parameter space. The vanishing of the phonon-mediated Casimir interaction between separate impurities can be understood on the same footing. We explore these remarkable phenomena by developing an effective low-energy theory that identifies the proper collective coordinates of the dressed impurity, and their coupling to the low-energy excitations of the host liquid. The main appeal of our approach lies in its ability to describe a dynamic response using effective parameters which obey exact thermodynamic relations. The latter may be extracted using powerful numerical or analytical techniques available in one-dimension, yielding asymptotically exact results for the low-energy impurity dynamics.

Subjects/Keywords: 1d quantum liquids; Bloch oscillations; Mobile impurity; Non-equilibrium transport; Superfluidity; Ultracold atoms; Physics

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Schecter, M. (2014). Dynamics of mobile impurities in one-dimensional quantum liquids. (Doctoral Dissertation). University of Minnesota. Retrieved from http://hdl.handle.net/11299/167460

Chicago Manual of Style (16th Edition):

Schecter, Michael. “Dynamics of mobile impurities in one-dimensional quantum liquids.” 2014. Doctoral Dissertation, University of Minnesota. Accessed November 14, 2019. http://hdl.handle.net/11299/167460.

MLA Handbook (7th Edition):

Schecter, Michael. “Dynamics of mobile impurities in one-dimensional quantum liquids.” 2014. Web. 14 Nov 2019.

Vancouver:

Schecter M. Dynamics of mobile impurities in one-dimensional quantum liquids. [Internet] [Doctoral dissertation]. University of Minnesota; 2014. [cited 2019 Nov 14]. Available from: http://hdl.handle.net/11299/167460.

Council of Science Editors:

Schecter M. Dynamics of mobile impurities in one-dimensional quantum liquids. [Doctoral Dissertation]. University of Minnesota; 2014. Available from: http://hdl.handle.net/11299/167460

.