Journal of Physics B Atomic Molecular and Optical Physics

Weizsäcker energy of unitary Fermi gas in a harmonic trap

Alexander L. Zubarev

Published Dec 12, 2008• 10 citations

Abstract

The universal method of construction of the rigorous lower bounds to the Weizsäcker energy is presented. We study a few-fermion system at unitarity. Upper and lower bounds to the density functional theory ground-state energy within the local density approximation are given. The rigorous lower bounds to the accuracy of the method are derived.

DOI: 10.1088/0953-4075/42/1/011001

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Weizsacker energy of unitary Fermi gas in a harmonic trap

Alexander L. Zubarev

The universal method of construction of the rigorous lower bounds to the Weizsäcker energy is presented. We study a few-fermion system at the unitarity. Upper and lower bounds to the density functional theory (DFT) ground state energy within the local density approximation (LDA) are given. The rigorous lower bounds to the accuracy of the method are derived. PACS numbers: 31.15.Ew, 71.15.Mb, 03.75.Ss

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The universal method of construction of the rigorous lower bounds to the Weizsacker energy is presented. We study a few-fermion systemat the unitarity. Upper and lower bounds to the density functional theory(DFT) ground state energy within the local density approximation (LDA) aregiven. Therigorous lower bounds to the accuracy of the method are derived.

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On the kinetic energy of unitary Fermi gas in a harmonic trap

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Journal of Physics B Atomic Molecular and Optical Physics

Weizsäcker energy of unitary Fermi gas in a harmonic trap

Alexander L. Zubarev

Published Dec 12, 2008• 10 citations

Publisher

Abstract

DOI: 10.1088/0953-4075/42/1/011001

Related papers

Weizsacker energy of unitary Fermi gas in a harmonic trap

Alexander L. Zubarev

APSMay 1, 20090 citations

Weizsacker energy of unitary Fermi gas in a harmonic trap

Alexander L. Zubarev

arXiv:0811.3352Nov 20, 20080 citations

Note on the bounds and approximations to the ground state energy of N-fermion systems derived from density matrix theory

F. David Peat

Canadian Journal of PhysicsJan 15, 19704 citations

On the kinetic energy of unitary Fermi gas in a harmonic trap

Alexander L. Zubarev, M. Zoubarev

We have considered the orbital-free approximation of the kinetic energy functional to investigate the zero temperature properties of dilute harmonically trapped two component Fermi gas at unitarity. It is shown that our approach provides a realible and inexpensive method to study superfluid strongly interacting dilute Fermi gases. PACS numbers: 31.15.Ew, 71.15.Mb, 03.75.SsThe modern density functional theory (DFT) is based on the Kohn-Sham (KS) approach [1], where the noninteracting kinetic energy, T, is calculated in terms of the KS orbitals, although Ref.[2] proved the basic existence of functional T(ρ), where ρ is the density, ρ(⃗r)dWe have considered the orbital-free approximation of the kinetic energy functional to investigate the zero temperature properties of dilute harmonically trapped two component Fermi gas at unitarity. It is shown that our approach provides a realible and inexpensive method to study superfluid strongly interacting dilute Fermi gases. PACS numbers: 31.15.Ew, 71.15.Mb, 03.75.SsThe modern density functional theory (DFT) is based on the Kohn-Sham (KS) approach [1], where the noninteracting kinetic energy, T, is calculated in terms of the KS orbitals, although Ref.[2] proved the basic existence of functional T(ρ), where ρ is the density, ρ(⃗r)d

Nov 27, 20123 citations

Ab initio simulation of the universal properties of unitary Fermi gas in a harmonic trap

Yunuo Xiong, Hongwei Xiong

Chang and Bertsch [Phys. Rev. A 76, 021603(R) (2007)] proposed a simple formula for the ground state energy of a unitary Fermi gas in a harmonic trap, based on their Green's function Monte Carlo simulations of up to 22 fermions, combined with general assumptions about the universal thermodynamic behavior of the unitary Fermi gas. In this work, we perform the ab initio simulations of the ground state energy of up to one hundred fermions using the fictitious identical particle method to overcome the Fermion sign problem, and we find that the formula proposed by Chang and Bertsch remains highly accurate. Since the number of fermions we simulate is much larger than that simulated by Chang and Bertsch when they proposed the formula, our work provides strong evidence for the universal validity of the formula. Our work demonstrates that fictitious identical particles provide a valuable tool for the ab initio simulations of ultracold Fermi gases.Chang and Bertsch [Phys. Rev. A 76, 021603(R) (2007)] proposed a simple formula for the ground state energy of a unitary Fermi gas in a harmonic trap, based on their Green's function Monte Carlo simulations of up to 22 fermions, combined with general assumptions about the universal thermodynamic behavior of the unitary Fermi gas. In this work, we perform the ab initio simulations of the ground state energy of up to one hundred fermions using the fictitious identical particle method to overcome the Fermion sign problem, and we find that the formula proposed by Chang and Bertsch remains highly accurate. Since the number of fermions we simulate is much larger than that simulated by Chang and Bertsch when they proposed the formula, our work provides strong evidence for the universal validity of the formula. Our work demonstrates that fictitious identical particles provide a valuable tool for the ab initio simulations of ultracold Fermi gases.

arXiv:2403.02961Mar 5, 20240 citations

Unitary Fermi gas in a harmonic trap

S. Y. Chang, G. F. Bertsch

We present an ab initio calculation of small numbers of trapped, strongly interacting fermions using the Green's function Monte Carlo method. The ground-state energy, density profile, and pairing gap are calculated for particle numbers $N=2--22$ using the parameter-free ``unitary'' interaction. Trial wave functions are taken in the form of correlated pairs in a harmonic oscillator basis. We find that the lowest energies are obtained with a minimum explicit pair correlation beyond that needed to exploit the degeneracy of oscillator states. We find that the energies can be well fitted by the expression ${a}_{\mathit{TF}}{E}_{\mathit{TF}}+\ensuremath{\Delta}\phantom{\rule{0.2em}{0ex}}\mathrm{mod}(N,2)$ where ${E}_{\mathit{TF}}$ is the Thomas-Fermi energy of a noninteracting gas in the trap and $\ensuremath{\Delta}$ is the pairing gap. There is no evidence of a shell correction energy in the systematics, but the density distributions show pronounced shell effects. We find the value $\ensuremath{\Delta}=0.7\ifmmode\pm\else\textpm\fi{}0.2\ensuremath{\omega}$ for the pairing gap. This is smaller than the value found for the uniform gas at a density corresponding to the central density of the trapped gas.We present an ab initio calculation of small numbers of trapped, strongly interacting fermions using the Green's function Monte Carlo method. The ground-state energy, density profile, and pairing gap are calculated for particle numbers $N=2--22$ using the parameter-free ``unitary'' interaction. Trial wave functions are taken in the form of correlated pairs in a harmonic oscillator basis. We find that the lowest energies are obtained with a minimum explicit pair correlation beyond that needed to exploit the degeneracy of oscillator states. We find that the energies can be well fitted by the expression ${a}_{\mathit{TF}}{E}_{\mathit{TF}}+\ensuremath{\Delta}\phantom{\rule{0.2em}{0ex}}\mathrm{mod}(N,2)$ where ${E}_{\mathit{TF}}$ is the Thomas-Fermi energy of a noninteracting gas in the trap and $\ensuremath{\Delta}$ is the pairing gap. There is no evidence of a shell correction energy in the systematics, but the density distributions show pronounced shell effects. We find the value $\ensuremath{\Delta}=0.7\ifmmode\pm\else\textpm\fi{}0.2\ensuremath{\omega}$ for the pairing gap. This is smaller than the value found for the uniform gas at a density corresponding to the central density of the trapped gas.

arXiv:physics/0703190Physical Review AAug 2, 200774 citations

N=2--22

using the parameter-free ``unitary'' interaction. Trial wave functions are taken in the form of correlated pairs in a harmonic oscillator basis. We find that the lowest energies are obtained with a minimum explicit pair correlation beyond that needed to exploit the degeneracy of oscillator states. We find that the energies can be well fitted by the expression ${a}_{\mathit{TF}}{E}_{\mathit{TF}}+\ensuremath{\Delta}\phantom{\rule{0.2em}{0ex}}\mathrm{mod}(N,2)$ where

{E}_{\mathit{TF}}

is the Thomas-Fermi energy of a noninteracting gas in the trap and $\ensuremath{\Delta}$ is the pairing gap. There is no evidence of a shell correction energy in the systematics, but the density distributions show pronounced shell effects. We find the value $\ensuremath{\Delta}=0.7\ifmmode\pm\else\textpm\fi{}0.2\ensuremath{\omega}$ for the pairing gap. This is smaller than the value found for the uniform gas at a density corresponding to the central density of the trapped gas.