arXiv subjects

E. B. Magnusson

Publications and source records attributed to E. B. Magnusson.

7 recordsLinked to original sources

arXiv2015

Surface acoustic wave resonators in the quantum regime

We present systematic measurements of the quality factors of surface acoustic wave (SAW) resonators on ST-X quartz in the gigahertz range at a temperature of $10 \, \textrm{mK}$. We demonstrate a internal quality factor $Q_\mathrm{i}$ approaching $0.5$ million at $0.5 \, \textrm{GHz}$ and show that $Q_\mathrm{i}\geq4.0\times10^4$ is achievable up to $4.4 \, \textrm{GHz}$. We show evidence for a polynomial dependence of propagation loss on frequency, as well as a weak drive power dependence of $Q_\mathrm{i}$ that saturates at low power, the latter being consistent with coupling to a bath of two-level systems. Our results indicate that SAW resonators are promising devices for integration with superconducting quantum circuits.

quant-ph↗

arXiv2013

Bistability phenomena in one-dimensional polariton wires

We investigate the phenomena of bistability and domain wall propagation in polaritonic systems with dissipation provided by the interaction with incoherent phonon bath. The results on the temperature dependence of the polariton bistability behavior and polariton neuron switching are presented.

cond-mat.mes-hall↗

arXiv2013

Density-matrix approach for an interacting polariton system

Using the Lindblad approach we develop a general formalism for theoretical description of a spatially inhomogeneous bosonic system with dissipation provided by the interaction of bosons with a phonon bath. We apply our results to model the dynamics of an interacting one-dimensional polariton system in real space and time, analyzing in detail the role of polariton-polariton and polariton-phonon interactions.

cond-mat.mes-hall↗

arXiv2012

Functional renormalization group approach to the singlet-triplet transition in quantum dots

We present a functional renormalization group approach to the zero bias transport properties of a quantum dot with two different orbitals and in presence of Hund's coupling. Tuning the energy separation of the orbital states, the quantum dot can be driven through a singlet-triplet transition. Our approach, based on the approach by Karrasch {\em et al} which we apply to spin-dependent interactions, recovers the key characteristics of the quantum dot transport properties with very little numerical effort. We present results on the conductance in the vicinity of the transition and compare our results both with previous numerical renormalization group results and with predictions of the perturbative renormalization group.

cond-mat.mes-hall↗

arXiv2012

Spin-orbit coupled cold exciton condensates

We analyze theoretically the dynamics of degenerate condensate of cold indirect excitons. We account for both linear spin dependent terms arising from spin-orbit interaction of Rashba and Dresselhaus types and non-linear terms transforming a pair of bright excitons into a pair of dark ones. We show that both terms should lead to the qualitative changes in the dynamics of cold exciton droplets in the real space and time.

cond-mat.mes-hall↗

arXiv2010

Fractional quantization of the ballistic conductance in electron and hole systems

In the present article we give a brief overview of the theories of the 0.7 anomaly of the ballistic conductance. The special attantion is given to the concept of a fractional quantization of the ballistic conductance arising from exchange interaction of the Heisenberg type between the carrier localized in the region of the quantum point contact and freely propagating carriers in electron and hole systems. ----- Brotaskömmtun skotleiðninnar í einvíðum rafeinda og holukerfum Í grein þessari verður skömmtun skotleiðninnar í einvíðum kerfum útskýrð og farið yfir nýjustu og helstu fræðilíkön á sviði \LDQ 0,7 fráviksins \RDQ og tengdra fyrirbrigða í einvíðum rafeinda og holukerfum. Við kynnum hugmynd okkar um að brotaskömmtun skotleiðninnar leiði af Heisenberg skiptaverkun milli staðbundins rafbera í skammtapunktsnertunni og frjálsra leiðnirafbera og sýnum fram á að hegðun leiðninnar er eigindlega ólík milli rafeinda og holukerfa.

cond-mat.mes-hall↗

arXiv2010

Phonon-mediated Josephson oscillations in excitonic and polaritonic condensates

We analyze theoretically the role of the exciton-phonon interactions in phenomena related to the Josephson effect between two spatially separated exciton and exciton-polariton condensates. We consider the role of the dephasing introduced by phonons in such phenomena as Josephson tunneling, self-trapping and spontaneous polarization separation. In the regime of cw pumping we find a remarkable bistability effect arising from exciton- exciton interactions as well as regimes of self- sustained regular and chaotic oscillations.

cond-mat.quant-gas↗