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Article: Quantum simulation of exotic PTinvariant topological nodal loop bands with ultracold atoms in an optical lattice
Title  Quantum simulation of exotic PTinvariant topological nodal loop bands with ultracold atoms in an optical lattice 

Authors  
Issue Date  2016 
Publisher  American Physical Society. The Journal's web site is located at http://pra.aps.org 
Citation  Physical Review A (Atomic, Molecular and Optical Physics), 2016, v. 93 n. 4, p. 043617: 110 How to Cite? 
Abstract  © 2016 American Physical Society.Since the wellknown PT symmetry has its fundamental significance and implication in physics, where PT denotes a joint operation of space inversion P and time reversal T, it is important and intriguing to explore exotic PTinvariant topological metals and to physically realize them. Here we develop a theory for a different type of topological metals that are described by a twoband model of PTinvariant topological nodal loop states in a threedimensional Brillouin zone, with the topological stability being revealed through the PTsymmetryprotected nontrivial Z2 topological charge even in the absence of both P and T symmetries. Moreover, the gapless boundary modes are demonstrated to originate from the nontrivial topological charge of the bulk nodal loop. Based on these exact results, we propose an experimental scheme to realize and to detect tunable PTinvariant topological nodal loop states with ultracold atoms in an optical lattice, in which atoms with two hyperfine spin states are loaded in a spindependent threedimensional optical lattice and two pairs of Raman lasers are used to create outofplane spinflip hopping with sitedependent phase. It is shown that such a realistic coldatom setup can yield topological nodal loop states, having a tunable bandtouching ring with the twofold degeneracy in the bulk spectrum and nontrivial surface states. The nodal loop states are actually protected by the combined PT symmetry and are characterized by a Z2type invariant (or topological charge), i.e., a quantized Berry phase. Remarkably, we demonstrate with numerical simulations that (i) the characteristic nodal ring can be detected by measuring the atomic transfer fractions in a BlochZener oscillation; (ii) the topological invariant may be measured based on the timeofflight imaging; and (iii) the surface states may be probed through Bragg spectroscopy. The present proposal for realizing topological nodal loop states in coldatom systems may provide a unique experimental platform for exploring exotic PTinvariant topological physics. 
Persistent Identifier  http://hdl.handle.net/10722/225656 
ISSN  2014 Impact Factor: 2.808 2015 SCImago Journal Rankings: 1.418 
DC Field  Value  Language 

dc.contributor.author  Zhang, DW   
dc.contributor.author  Zhao, YX   
dc.contributor.author  Liu, RB   
dc.contributor.author  Xue, ZY   
dc.contributor.author  Zhu, SL   
dc.contributor.author  Wang, Z   
dc.date.accessioned  20160520T08:09:48Z   
dc.date.available  20160520T08:09:48Z   
dc.date.issued  2016   
dc.identifier.citation  Physical Review A (Atomic, Molecular and Optical Physics), 2016, v. 93 n. 4, p. 043617: 110   
dc.identifier.issn  10502947   
dc.identifier.uri  http://hdl.handle.net/10722/225656   
dc.description.abstract  © 2016 American Physical Society.Since the wellknown PT symmetry has its fundamental significance and implication in physics, where PT denotes a joint operation of space inversion P and time reversal T, it is important and intriguing to explore exotic PTinvariant topological metals and to physically realize them. Here we develop a theory for a different type of topological metals that are described by a twoband model of PTinvariant topological nodal loop states in a threedimensional Brillouin zone, with the topological stability being revealed through the PTsymmetryprotected nontrivial Z2 topological charge even in the absence of both P and T symmetries. Moreover, the gapless boundary modes are demonstrated to originate from the nontrivial topological charge of the bulk nodal loop. Based on these exact results, we propose an experimental scheme to realize and to detect tunable PTinvariant topological nodal loop states with ultracold atoms in an optical lattice, in which atoms with two hyperfine spin states are loaded in a spindependent threedimensional optical lattice and two pairs of Raman lasers are used to create outofplane spinflip hopping with sitedependent phase. It is shown that such a realistic coldatom setup can yield topological nodal loop states, having a tunable bandtouching ring with the twofold degeneracy in the bulk spectrum and nontrivial surface states. The nodal loop states are actually protected by the combined PT symmetry and are characterized by a Z2type invariant (or topological charge), i.e., a quantized Berry phase. Remarkably, we demonstrate with numerical simulations that (i) the characteristic nodal ring can be detected by measuring the atomic transfer fractions in a BlochZener oscillation; (ii) the topological invariant may be measured based on the timeofflight imaging; and (iii) the surface states may be probed through Bragg spectroscopy. The present proposal for realizing topological nodal loop states in coldatom systems may provide a unique experimental platform for exploring exotic PTinvariant topological physics.   
dc.language  eng   
dc.publisher  American Physical Society. The Journal's web site is located at http://pra.aps.org   
dc.relation.ispartof  Physical Review A (Atomic, Molecular and Optical Physics)   
dc.rights  Physical Review A (Atomic, Molecular and Optical Physics). Copyright © American Physical Society.   
dc.rights  Creative Commons: Attribution 3.0 Hong Kong License   
dc.title  Quantum simulation of exotic PTinvariant topological nodal loop bands with ultracold atoms in an optical lattice   
dc.type  Article   
dc.identifier.email  Zhao, YX: yuxinphy@hku.hk   
dc.identifier.email  Wang, Z: zwang@hku.hk   
dc.identifier.authority  Wang, Z=rp00802   
dc.description.nature  postprint   
dc.identifier.doi  10.1103/PhysRevA.93.043617   
dc.identifier.scopus  eid_2s2.084964374748   
dc.identifier.hkuros  257933   
dc.identifier.volume  93   
dc.identifier.issue  4   
dc.identifier.spage  043617: 1   
dc.identifier.epage  043617:10   
dc.publisher.place  United States   