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Subir Sachdev - One of the best experts on this subject based on the ideXlab platform.
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quantum field theory for the chiral clock transition in one Spatial dimension
Physical Review B, 2018Co-Authors: Rhine Samajdar, Subir Sachdev, Seth WhitsittAbstract:We describe the quantum phase transition in the $N$-state chiral clock model in Spatial dimension $d=1$. With couplings chosen to preserve time-reversal and Spatial Inversion symmetries, such a model is in the universality class of recent experimental studies of the ordering of pumped Rydberg states in a one-dimensional chain of trapped ultracold alkali atoms. For such couplings and $N=3$, the clock model is expected to have a direct phase transition from a gapped phase with a broken global $\mathbb{Z}_N$ symmetry, to a gapped phase with the $\mathbb{Z}_N$ symmetry restored. The transition has dynamical critical exponent $z \neq 1$, and so cannot be described by a relativistic quantum field theory. We use a lattice duality transformation to map the transition onto that of a Bose gas in $d=1$, involving the onset of a single boson condensate in the background of a higher-dimensional $N$-boson condensate. We present a renormalization group analysis of the strongly coupled field theory for the Bose gas transition in an expansion in $2-d$, with $4-N$ chosen to be of order $2-d$. At two-loop order, we find a regime of parameters with a renormalization group fixed point which can describe a direct phase transition. We also present numerical density-matrix renormalization group studies of lattice chiral clock and Bose gas models for $N=3$, finding good evidence for a direct phase transition, and obtain estimates for $z$ and the correlation length exponent $\nu$.
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quantum field theory for the chiral clock transition in one Spatial dimension
Physical Review B, 2018Co-Authors: Rhine Samajdar, Subir Sachdev, Seth WhitsittAbstract:We describe the quantum phase transition in the $N$-state chiral clock model in Spatial dimension $d=1$. With couplings chosen to preserve time-reversal and Spatial Inversion symmetries, such a model is in the universality class of recent experimental studies of the ordering of pumped Rydberg states in a one-dimensional chain of trapped ultracold alkali atoms. For such couplings and $N=3$, the clock model is expected to have a direct phase transition from a gapped phase with a broken global ${\mathbb{Z}}_{N}$ symmetry, to a gapped phase with the ${\mathbb{Z}}_{N}$ symmetry restored. The transition has dynamical critical exponent $z\ensuremath{\ne}1$, and so cannot be described by a relativistic quantum field theory. We use a lattice duality transformation to map the transition onto that of a Bose gas in $d=1$, involving the onset of a single-boson condensate in the background of a higher-dimensional $N$-boson condensate. We present a renormalization group analysis of the strongly coupled field theory for the Bose gas transition in an expansion in $2\ensuremath{-}d$, with $4\ensuremath{-}N$ chosen to be of order $2\ensuremath{-}d$. At two-loop order, we find a regime of parameters with a renormalization group fixed point which can describe a direct phase transition. We also present numerical density-matrix renormalization group studies of lattice chiral clock and Bose gas models for $N=3$, finding good evidence for a direct phase transition, and obtain estimates for $z$ and the correlation length exponent $\ensuremath{\nu}$.
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numerical study of the chiral z 3 quantum phase transition in one Spatial dimension
Physical Review A, 2018Co-Authors: Rhine Samajdar, Soonwon Choi, Hannes Pichler, Mikhail D Lukin, Subir SachdevAbstract:Recent experiments on a one-dimensional chain of trapped alkali-metal atoms [Bernien et al., Nature (London) 551, 579 (2017)] have observed a quantum transition associated with the onset of period-3 ordering of pumped Rydberg states. This spontaneous ${\mathbb{Z}}_{3}$ symmetry breaking is described by a constrained model of hard-core bosons proposed by Fendley et al. [Phys. Rev. B 69, 075106 (2004)]. By symmetry arguments, the transition is expected to be in the universality class of the ${\mathbb{Z}}_{3}$ chiral clock model with parameters preserving both time-reversal and Spatial-Inversion symmetries. We study the nature of the order--disorder transition in these models and numerically calculate its critical exponents with exact diagonalization and density-matrix renormalization-group techniques. We use finite-size scaling to determine the dynamical critical exponent $z$ and the correlation length exponent $\ensuremath{\nu}$. Our analysis presents the only known instance of a strongly coupled generic transition between gapped states with $z\ensuremath{\ne}1$, implying an underlying nonconformal critical-field theory.
Seth Whitsitt - One of the best experts on this subject based on the ideXlab platform.
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quantum field theory for the chiral clock transition in one Spatial dimension
Physical Review B, 2018Co-Authors: Rhine Samajdar, Subir Sachdev, Seth WhitsittAbstract:We describe the quantum phase transition in the $N$-state chiral clock model in Spatial dimension $d=1$. With couplings chosen to preserve time-reversal and Spatial Inversion symmetries, such a model is in the universality class of recent experimental studies of the ordering of pumped Rydberg states in a one-dimensional chain of trapped ultracold alkali atoms. For such couplings and $N=3$, the clock model is expected to have a direct phase transition from a gapped phase with a broken global ${\mathbb{Z}}_{N}$ symmetry, to a gapped phase with the ${\mathbb{Z}}_{N}$ symmetry restored. The transition has dynamical critical exponent $z\ensuremath{\ne}1$, and so cannot be described by a relativistic quantum field theory. We use a lattice duality transformation to map the transition onto that of a Bose gas in $d=1$, involving the onset of a single-boson condensate in the background of a higher-dimensional $N$-boson condensate. We present a renormalization group analysis of the strongly coupled field theory for the Bose gas transition in an expansion in $2\ensuremath{-}d$, with $4\ensuremath{-}N$ chosen to be of order $2\ensuremath{-}d$. At two-loop order, we find a regime of parameters with a renormalization group fixed point which can describe a direct phase transition. We also present numerical density-matrix renormalization group studies of lattice chiral clock and Bose gas models for $N=3$, finding good evidence for a direct phase transition, and obtain estimates for $z$ and the correlation length exponent $\ensuremath{\nu}$.
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quantum field theory for the chiral clock transition in one Spatial dimension
Physical Review B, 2018Co-Authors: Rhine Samajdar, Subir Sachdev, Seth WhitsittAbstract:We describe the quantum phase transition in the $N$-state chiral clock model in Spatial dimension $d=1$. With couplings chosen to preserve time-reversal and Spatial Inversion symmetries, such a model is in the universality class of recent experimental studies of the ordering of pumped Rydberg states in a one-dimensional chain of trapped ultracold alkali atoms. For such couplings and $N=3$, the clock model is expected to have a direct phase transition from a gapped phase with a broken global $\mathbb{Z}_N$ symmetry, to a gapped phase with the $\mathbb{Z}_N$ symmetry restored. The transition has dynamical critical exponent $z \neq 1$, and so cannot be described by a relativistic quantum field theory. We use a lattice duality transformation to map the transition onto that of a Bose gas in $d=1$, involving the onset of a single boson condensate in the background of a higher-dimensional $N$-boson condensate. We present a renormalization group analysis of the strongly coupled field theory for the Bose gas transition in an expansion in $2-d$, with $4-N$ chosen to be of order $2-d$. At two-loop order, we find a regime of parameters with a renormalization group fixed point which can describe a direct phase transition. We also present numerical density-matrix renormalization group studies of lattice chiral clock and Bose gas models for $N=3$, finding good evidence for a direct phase transition, and obtain estimates for $z$ and the correlation length exponent $\nu$.
Yoji Ohashi - One of the best experts on this subject based on the ideXlab platform.
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triplet pair amplitude in a trapped s wave superfluid fermi gas with broken spin rotation symmetry ii three dimensional continuum case
Physical Review A, 2016Co-Authors: Daisuke Inotani, Ryo Hanai, Yoji OhashiAbstract:We extend our recent work [Y. Endo et al., Phys. Rev. A 92, 023610 (2015)] for a parity-mixing effect in a model of two-dimensional lattice fermions to a realistic three-dimensional ultracold Fermi gas. Including effects of broken local Spatial Inversion symmetry by a trap potential within the framework of the real-space Bogoliubov-de Gennes theory at $T=0$, we point out that an odd-parity $p\text{-wave}$ Cooper-pair amplitude is expected to have already been realized in previous experiments on an (even-parity) $s\text{-wave}$ superfluid Fermi gas with spin imbalance. This indicates that when one suddenly changes the $s\text{-wave}$ pairing interaction to an appropriate $p\text{-wave}$ one by using a Feshbach technique in this case, a nonvanishing $p\text{-wave}$ superfluid order parameter is immediately obtained, which is given by the product of the $p\text{-wave}$ interaction and the $p\text{-wave}$ pair amplitude that has already been induced in the spin-imbalanced $s\text{-wave}$ superfluid Fermi gas. Thus, by definition, the system is in the $p\text{-wave}$ superfluid state, at least just after this manipulation. Since the achievement of a $p\text{-wave}$ superfluid state is one of the most exciting challenges in cold Fermi gas physics, our results may provide an alternative approach to this unconventional pairing state. In addition, since the parity-mixing effect cannot be explained as far as one deals with a trap potential in the local density approximation (LDA), it is considered as a crucial example which requires us to go beyond the LDA.
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triplet pair amplitude in a trapped s wave superfluid fermi gas with broken spin rotation symmetry
Physical Review A, 2015Co-Authors: Yuki Endo, Daisuke Inotani, Ryo Hanai, Yoji OhashiAbstract:We investigate the possibility that the broken Spatial Inversion symmetry by a trap potential induces a spin-triplet Cooper-pair amplitude in an s-wave superfluid Fermi gas. Being based on symmetry considerations, we clarify that this phenomenon may occur, when a spin rotation symmetry of the system is also broken. We also numerically confirm that a triplet pair amplitude is really induced under this condition, using a simple model. Our results imply that this phenomenon is already present in a trapped s-wave superfluid Fermi gas with spin imbalance. As an interesting application of this phenomenon, we point out that one may produce a p-wave superfluid Fermi gas, by suddenly changing the s-wave pairing interaction to a p-wave one by using the Feshbach resonance technique. Since a Cooper pair is usually classified into the spin-singlet (and even-parity) state and the spin-triplet (and odd-parity) state, our results would be useful in considering how to mix them with each other in a superfluid Fermi gas. Such admixture has recently attracted much attention in the field of non-centrosymmetric superconductivity, so that our results would also contribute to the further development of this research field, on the viewpoint of cold Fermi gas physics.
Rhine Samajdar - One of the best experts on this subject based on the ideXlab platform.
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quantum field theory for the chiral clock transition in one Spatial dimension
Physical Review B, 2018Co-Authors: Rhine Samajdar, Subir Sachdev, Seth WhitsittAbstract:We describe the quantum phase transition in the $N$-state chiral clock model in Spatial dimension $d=1$. With couplings chosen to preserve time-reversal and Spatial Inversion symmetries, such a model is in the universality class of recent experimental studies of the ordering of pumped Rydberg states in a one-dimensional chain of trapped ultracold alkali atoms. For such couplings and $N=3$, the clock model is expected to have a direct phase transition from a gapped phase with a broken global $\mathbb{Z}_N$ symmetry, to a gapped phase with the $\mathbb{Z}_N$ symmetry restored. The transition has dynamical critical exponent $z \neq 1$, and so cannot be described by a relativistic quantum field theory. We use a lattice duality transformation to map the transition onto that of a Bose gas in $d=1$, involving the onset of a single boson condensate in the background of a higher-dimensional $N$-boson condensate. We present a renormalization group analysis of the strongly coupled field theory for the Bose gas transition in an expansion in $2-d$, with $4-N$ chosen to be of order $2-d$. At two-loop order, we find a regime of parameters with a renormalization group fixed point which can describe a direct phase transition. We also present numerical density-matrix renormalization group studies of lattice chiral clock and Bose gas models for $N=3$, finding good evidence for a direct phase transition, and obtain estimates for $z$ and the correlation length exponent $\nu$.
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quantum field theory for the chiral clock transition in one Spatial dimension
Physical Review B, 2018Co-Authors: Rhine Samajdar, Subir Sachdev, Seth WhitsittAbstract:We describe the quantum phase transition in the $N$-state chiral clock model in Spatial dimension $d=1$. With couplings chosen to preserve time-reversal and Spatial Inversion symmetries, such a model is in the universality class of recent experimental studies of the ordering of pumped Rydberg states in a one-dimensional chain of trapped ultracold alkali atoms. For such couplings and $N=3$, the clock model is expected to have a direct phase transition from a gapped phase with a broken global ${\mathbb{Z}}_{N}$ symmetry, to a gapped phase with the ${\mathbb{Z}}_{N}$ symmetry restored. The transition has dynamical critical exponent $z\ensuremath{\ne}1$, and so cannot be described by a relativistic quantum field theory. We use a lattice duality transformation to map the transition onto that of a Bose gas in $d=1$, involving the onset of a single-boson condensate in the background of a higher-dimensional $N$-boson condensate. We present a renormalization group analysis of the strongly coupled field theory for the Bose gas transition in an expansion in $2\ensuremath{-}d$, with $4\ensuremath{-}N$ chosen to be of order $2\ensuremath{-}d$. At two-loop order, we find a regime of parameters with a renormalization group fixed point which can describe a direct phase transition. We also present numerical density-matrix renormalization group studies of lattice chiral clock and Bose gas models for $N=3$, finding good evidence for a direct phase transition, and obtain estimates for $z$ and the correlation length exponent $\ensuremath{\nu}$.
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numerical study of the chiral z 3 quantum phase transition in one Spatial dimension
Physical Review A, 2018Co-Authors: Rhine Samajdar, Soonwon Choi, Hannes Pichler, Mikhail D Lukin, Subir SachdevAbstract:Recent experiments on a one-dimensional chain of trapped alkali-metal atoms [Bernien et al., Nature (London) 551, 579 (2017)] have observed a quantum transition associated with the onset of period-3 ordering of pumped Rydberg states. This spontaneous ${\mathbb{Z}}_{3}$ symmetry breaking is described by a constrained model of hard-core bosons proposed by Fendley et al. [Phys. Rev. B 69, 075106 (2004)]. By symmetry arguments, the transition is expected to be in the universality class of the ${\mathbb{Z}}_{3}$ chiral clock model with parameters preserving both time-reversal and Spatial-Inversion symmetries. We study the nature of the order--disorder transition in these models and numerically calculate its critical exponents with exact diagonalization and density-matrix renormalization-group techniques. We use finite-size scaling to determine the dynamical critical exponent $z$ and the correlation length exponent $\ensuremath{\nu}$. Our analysis presents the only known instance of a strongly coupled generic transition between gapped states with $z\ensuremath{\ne}1$, implying an underlying nonconformal critical-field theory.
M Kenzelmann - One of the best experts on this subject based on the ideXlab platform.
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magnetic Inversion symmetry breaking and ferroelectricity in tbmno3
Physical Review Letters, 2005Co-Authors: M Kenzelmann, A B Harris, S Jonas, C Broholm, J Schefer, S B Kim, C L Zhang, S W Cheong, O P Vajk, J W LynnAbstract:TbMnO3 is an orthorhombic insulator where incommensurate spin order for temperature T_N < 41K is accompanied by ferroelectric order for T < 28K. To understand this, we establish the magnetic structure above and below the ferroelectric transition using neutron diffraction. In the paraelectric phase, the spin structure is incommensurate and longitudinally-modulated. In the ferroelectric phase, however, there is a transverse incommensurate spiral. We show that the spiral breaks Spatial Inversion symmetry and can account for magnetoelectricity in TbMnO3.
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magnetic Inversion symmetry breaking and ferroelectricity in tbmno3
Physical Review Letters, 2005Co-Authors: M Kenzelmann, A B Harris, S Jonas, C Broholm, J Schefer, S B Kim, Chenglin Zhang, Sangwook CheongAbstract:${\mathrm{TbMnO}}_{3}$ is an orthorhombic insulator where incommensurate spin order for temperature ${T}_{N}l41\text{ }\text{ }\mathrm{K}$ is accompanied by ferroelectric order for $Tl28\text{ }\text{ }\mathrm{K}$. To understand this, we establish the magnetic structure above and below the ferroelectric transition using neutron diffraction. In the paraelectric phase, the spin structure is incommensurate and longitudinally modulated. In the ferroelectric phase, however, there is a transverse incommensurate spiral. We show that the spiral breaks Spatial Inversion symmetry and can account for magnetoelectricity in ${\mathrm{TbMnO}}_{3}$.