Imperial College London
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DrRyanBarnett

Faculty of Natural Sciences, Department of Mathematics

Reader in Condensed Matter Theory
 
 
 
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Contact

 

+44 (0)20 7594 8536r.barnett Website

 
 
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Location

 

6M49Huxley BuildingSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{Barnett:2016:10.1103/PhysRevA.94.023605,
author = {Barnett, RL and Payrits, M},
doi = {10.1103/PhysRevA.94.023605},
journal = {Physical Review A},
title = {Quantum Rotor Theory of Systems of Spin-2 Bosons},
url = {http://dx.doi.org/10.1103/PhysRevA.94.023605},
volume = {94},
year = {2016}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - We consider quantum phases of tightly-confined spin-2 bosons in an external field under thepresence of rotationally-invariant interactions. Generalizing previous treatments, we show how thissystem can be mapped onto a quantum rotor model. Within the rotor framework, low-energy excitationsabout fragmented states, which cannot be accessed within standard Bogoliubov theory, canbe obtained. In the spatially extended system in the thermodynamic limit there exists a mean-fieldground state degeneracy between a family of nematic states for appropriate interaction parameters.It has been established that quantum fluctuations lift this degeneracy through the mechanism oforder-by-disorder and select either a uniaxial or square-biaxial ground state. On the other hand, inthe full quantum treatment of the analogous single-spatial mode problem with finite particle numberit is known that, due to symmetry restoring fluctuations, there is a unique ground state across theentire nematic region of the phase diagram. Within the established rotor framework we investigatethe possible quantum phases under the presence of a quadratic Zeeman field, a problem which haspreviously received little attention. By investigating wave function overlaps we do not find anysignatures of the order-by-disorder phenomenon which is present in the continuum case. Motivatedby this we consider an alternative external potential which breaks less symmetry than the quadraticZeeman field. For this case we do find the phenomenon of order-by-disorder in the fully quantumsystem. This is established within the rotor framework and with exact diagonalization.
AU  - Barnett,RL
AU  - Payrits,M
DO  - 10.1103/PhysRevA.94.023605
PY  - 2016///
SN  - 1094-1622
TI  - Quantum Rotor Theory of Systems of Spin-2 Bosons
T2  - Physical Review A
UR  - http://dx.doi.org/10.1103/PhysRevA.94.023605
UR  - http://hdl.handle.net/10044/1/38606
VL  - 94
ER  -
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