1
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Li X, Wang S, Luo X, Zhou YY, Xie K, Shen HC, Nie YZ, Chen Q, Hu H, Chen YA, Yao XC, Pan JW. Observation and quantification of the pseudogap in unitary Fermi gases. Nature 2024; 626:288-293. [PMID: 38326594 DOI: 10.1038/s41586-023-06964-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2023] [Accepted: 12/12/2023] [Indexed: 02/09/2024]
Abstract
The microscopic origin of high-temperature superconductivity in cuprates remains unknown. It is widely believed that substantial progress could be achieved by better understanding of the pseudogap phase, a normal non-superconducting state of cuprates1,2. In particular, a central issue is whether the pseudogap could originate from strong pairing fluctuations3. Unitary Fermi gases4,5, in which the pseudogap-if it exists-necessarily arises from many-body pairing, offer ideal quantum simulators to address this question. Here we report the observation of a pair-fluctuation-driven pseudogap in homogeneous unitary Fermi gases of lithium-6 atoms, by precisely measuring the fermion spectral function through momentum-resolved microwave spectroscopy and without spurious effects from final-state interactions. The temperature dependence of the pairing gap, inverse pair lifetime and single-particle scattering rate are quantitatively determined by analysing the spectra. We find a large pseudogap above the superfluid transition temperature. The inverse pair lifetime exhibits a thermally activated exponential behaviour, uncovering the microscopic virtual pair breaking and recombination mechanism. The obtained large, temperature-independent single-particle scattering rate is comparable with that set by the Planckian limit6. Our findings quantitatively characterize the pseudogap in strongly interacting Fermi gases and they lend support for the role of preformed pairing as a precursor to superfluidity.
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Affiliation(s)
- Xi Li
- Hefei National Research Center for Physical Sciences at the Microscale and School of Physical Sciences, University of Science and Technology of China, Hefei, China
- Shanghai Research Center for Quantum Science and CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei, China
| | - Shuai Wang
- Hefei National Research Center for Physical Sciences at the Microscale and School of Physical Sciences, University of Science and Technology of China, Hefei, China
- Shanghai Research Center for Quantum Science and CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai, China
| | - Xiang Luo
- Hefei National Research Center for Physical Sciences at the Microscale and School of Physical Sciences, University of Science and Technology of China, Hefei, China
- Shanghai Research Center for Quantum Science and CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai, China
| | - Yu-Yang Zhou
- Hefei National Research Center for Physical Sciences at the Microscale and School of Physical Sciences, University of Science and Technology of China, Hefei, China
- Shanghai Research Center for Quantum Science and CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai, China
| | - Ke Xie
- Hefei National Research Center for Physical Sciences at the Microscale and School of Physical Sciences, University of Science and Technology of China, Hefei, China
- Shanghai Research Center for Quantum Science and CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai, China
| | - Hong-Chi Shen
- Hefei National Research Center for Physical Sciences at the Microscale and School of Physical Sciences, University of Science and Technology of China, Hefei, China
- Shanghai Research Center for Quantum Science and CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai, China
| | - Yu-Zhao Nie
- Hefei National Research Center for Physical Sciences at the Microscale and School of Physical Sciences, University of Science and Technology of China, Hefei, China
- Shanghai Research Center for Quantum Science and CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai, China
| | - Qijin Chen
- Hefei National Research Center for Physical Sciences at the Microscale and School of Physical Sciences, University of Science and Technology of China, Hefei, China
- Shanghai Research Center for Quantum Science and CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei, China
| | - Hui Hu
- Hefei National Research Center for Physical Sciences at the Microscale and School of Physical Sciences, University of Science and Technology of China, Hefei, China
- Centre for Quantum Technology Theory, Swinburne University of Technology, Melbourne, Victoria, Australia
| | - Yu-Ao Chen
- Hefei National Research Center for Physical Sciences at the Microscale and School of Physical Sciences, University of Science and Technology of China, Hefei, China.
- Shanghai Research Center for Quantum Science and CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai, China.
- Hefei National Laboratory, University of Science and Technology of China, Hefei, China.
| | - Xing-Can Yao
- Hefei National Research Center for Physical Sciences at the Microscale and School of Physical Sciences, University of Science and Technology of China, Hefei, China.
- Shanghai Research Center for Quantum Science and CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai, China.
- Hefei National Laboratory, University of Science and Technology of China, Hefei, China.
| | - Jian-Wei Pan
- Hefei National Research Center for Physical Sciences at the Microscale and School of Physical Sciences, University of Science and Technology of China, Hefei, China.
- Shanghai Research Center for Quantum Science and CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai, China.
- Hefei National Laboratory, University of Science and Technology of China, Hefei, China.
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2
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Baten RN, Tian Y, Smith EN, Mueller EJ, Parpia JM. Observation of suppressed viscosity in the normal state of 3He due to superfluid fluctuations. Nat Commun 2023; 14:5834. [PMID: 37730714 PMCID: PMC10511454 DOI: 10.1038/s41467-023-41422-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 08/31/2023] [Indexed: 09/22/2023] Open
Abstract
Evidence of fluctuations in transport have long been predicted in 3He. They are expected to contribute only within 100μK of Tc and play a vital role in the theoretical modeling of ordering; they encode details about the Fermi liquid parameters, pairing symmetry, and scattering phase shifts. It is expected that they will be of crucial importance for transport probes of the topologically nontrivial features of superfluid 3He under strong confinement. Here we characterize the temperature and pressure dependence of the fluctuation signature, by monitoring the quality factor of a quartz tuning fork oscillator. We have observed a fluctuation-driven reduction in the viscosity of bulk 3He, finding data collapse consistent with the predicted theoretical behavior.
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Affiliation(s)
- Rakin N Baten
- Department of Physics, Cornell University, Ithaca, NY, 14853, USA
| | - Yefan Tian
- Department of Physics, Cornell University, Ithaca, NY, 14853, USA
| | - Eric N Smith
- Department of Physics, Cornell University, Ithaca, NY, 14853, USA
| | - Erich J Mueller
- Department of Physics, Cornell University, Ithaca, NY, 14853, USA
| | - Jeevak M Parpia
- Department of Physics, Cornell University, Ithaca, NY, 14853, USA.
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3
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Jang H, Thi Anh Hong V, Kim J, Lu X, Park T. Hybridization-Controlled Pseudogap State in the Quantum Critical Superconductor CeCoIn_{5}. PHYSICAL REVIEW LETTERS 2023; 130:076301. [PMID: 36867818 DOI: 10.1103/physrevlett.130.076301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2022] [Accepted: 01/23/2023] [Indexed: 06/18/2023]
Abstract
The origin of the partial suppression of the electronic density states in the enigmatic pseudogap behavior, which is at the core of understanding high-T_{c} superconductivity, has been hotly contested as either a hallmark of preformed Cooper pairs or an incipient order of competing interactions nearby. Here, we report the quasiparticle scattering spectroscopy of the quantum critical superconductor CeCoIn_{5}, where a pseudogap with energy Δ_{g} was manifested as a dip in the differential conductance (dI/dV) below the characteristic temperature of T_{g}. When subjected to external pressure, T_{g} and Δ_{g} gradually increase, following the trend of increase in quantum entangled hybridization between the Ce 4f moment and conduction electrons. On the other hand, the superconducting (SC) energy gap and its phase transition temperature shows a maximum, revealing a dome shape under pressure. The disparate dependence on pressure between the two quantum states shows that the pseudogap is less likely involved in the formation of SC Cooper pairs, but rather is controlled by Kondo hybridization, indicating that a novel type of pseudogap is realized in CeCoIn_{5}.
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Affiliation(s)
- Harim Jang
- Department of Physics, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Vuong Thi Anh Hong
- Department of Physics, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Jihyun Kim
- Department of Physics, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Xin Lu
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou 310058, China
| | - Tuson Park
- Department of Physics, Sungkyunkwan University, Suwon 16419, Republic of Korea
- Center for Quantum Materials and Superconductivity (CQMS), Sungkyunkwan University, Suwon 16419, Republic of Korea
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4
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Pseudo-Conformal Sound Speed in the Core of Compact Stars. Symmetry (Basel) 2022. [DOI: 10.3390/sym14102154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
By implementing the putative “hadron-quark continuity” conjectured in QCD in terms of skyrmion-half-skyrmion topological change in an effective field theory for dense matter, we argue that (quasi-)baryons could “masquerade” deconfined quarks in the interior of compact stars. We interpret this phenomenon as a consequence of possible interplay between hidden scale symmetry and hidden local symmetry at high density. A surprising spin-off of the emerging symmetry that we call “pseudo-conformality” is that the long-standing puzzle of the quenched gA≈1 in nuclei can be given a simple resolution by the way the hidden symmetries impact nuclear dynamics at low density.
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5
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Dichotomy of Baryons as Quantum Hall Droplets and Skyrmions: Topological Structure of Dense Matter. Symmetry (Basel) 2021. [DOI: 10.3390/sym13101888] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
We review a new development on the possible direct connection between the topological structure of the Nf=1 baryon as a FQH droplet and that of the Nf≥2 baryons (such as nucleons and hyperons) as skyrmions. This development suggests a possible “domain-wall (DW)” structure of compressed baryonic matter at high density expected to be found in the core of massive compact stars. Our theoretical framework is anchored on an effective nuclear effective field theory that incorporates two symmetries either hidden in the vacuum in QCD or emergent from strong nuclear correlations. It presents a basically different, hitherto undiscovered structure of nuclear matter at low as well as high densities. Hidden “genuine dilaton (GD)” symmetry and hidden local symmetry (HLS) gauge-equivalent at low density to nonlinear sigma model capturing chiral symmetry, put together in nuclear effective field theory, are seen to play an increasingly important role in providing hadron–quark duality in baryonic matter. It is argued that the FQH droplets could actually figure essentially in the properties of the vector mesons endowed with HLS near chiral restoration. This strongly motivates incorporating both symmetries in formulating “first-principles” approaches to nuclear dynamics encompassing from the nuclear matter density to the highest density stable in the Universe.
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6
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Long Y, Xiong F, Parker CV. Spin Susceptibility above the Superfluid Onset in Ultracold Fermi Gases. PHYSICAL REVIEW LETTERS 2021; 126:153402. [PMID: 33929234 DOI: 10.1103/physrevlett.126.153402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 10/01/2020] [Accepted: 03/02/2021] [Indexed: 06/12/2023]
Abstract
Ultracold atomic Fermi gases can be tuned to interact strongly, which produces a display of spectroscopic signatures above the superfluid transition reminiscent of the pseudogap in cuprates. However, the extent of the analogy can be questioned since many thermodynamic quantities in the low temperature spin-imbalanced normal state can be described successfully using Fermi liquid theory. Here we present spin susceptibility measurements across the interaction strength-temperature phase diagram using a novel radio frequency technique with ultracold ^{6}Li gases. For all significant interaction strengths and at all temperatures we find the spin susceptibility is reduced compared to the equivalent value for a noninteracting Fermi gas. At unitarity, we can use the local density approximation to extract the integrated spin susceptibility for the uniform gas as a function of temperature, which at high temperatures is generally less than theoretically predicted. At low temperatures, our data lie within the range of theoretical predictions, although we can also describe the entire curve using a very simple one-parameter mean field model with monotonically increasing spin susceptibility.
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Affiliation(s)
- Yun Long
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | - Feng Xiong
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | - Colin V Parker
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
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7
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Hidden Pseudogap and Excitation Spectra in a Strongly Coupled Two-Band Superfluid/Superconductor. CONDENSED MATTER 2021. [DOI: 10.3390/condmat6010008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We investigate single-particle excitation properties in the normal state of a two-band superconductor or superfluid throughout the Bardeen–Cooper–Schrieffer (BCS) to Bose–Einstein-condensation (BEC) crossover, within the many-body T-matrix approximation for multichannel pairing fluctuations. We address the single-particle density of states and the spectral functions consisting of two contributions associated with a weakly interacting deep band and a strongly interacting shallow band, relevant for iron-based multiband superconductors and multicomponent fermionic superfluids. We show how the pseudogap state in the shallow band is hidden by the deep band contribution throughout the two-band BCS-BEC crossover. Our results could explain the missing pseudogap in recent scanning tunneling microscopy experiments in FeSe superconductors.
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8
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Richie-Halford A, Drut JE, Bulgac A. Emergence of a Pseudogap in the BCS-BEC Crossover. PHYSICAL REVIEW LETTERS 2020; 125:060403. [PMID: 32845679 DOI: 10.1103/physrevlett.125.060403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Accepted: 07/13/2020] [Indexed: 06/11/2023]
Abstract
Strongly correlated Fermi systems with pairing interactions become superfluid below a critical temperature T_{c}. The extent to which such pairing correlations alter the behavior of the liquid at temperatures T>T_{c} is a subtle issue that remains an area of debate, in particular regarding the appearance of the so-called pseudogap in the BCS-BEC crossover of unpolarized spin-1/2 nonrelativistic matter. To shed light on this, we extract several quantities of crucial importance at and around the unitary limit, namely, the odd-even staggering of the total energy, the spin susceptibility, the pairing correlation function, the condensate fraction, and the critical temperature T_{c}, using a nonperturbative, constrained-ensemble quantum Monte Carlo algorithm.
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Affiliation(s)
- Adam Richie-Halford
- Department of Physics, University of Washington, Seattle, Washington 98195-1560, USA
| | - Joaquín E Drut
- Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - Aurel Bulgac
- Department of Physics, University of Washington, Seattle, Washington 98195-1560, USA
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9
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Hou Y, Drut JE. Fourth- and Fifth-Order Virial Coefficients from Weak Coupling to Unitarity. PHYSICAL REVIEW LETTERS 2020; 125:050403. [PMID: 32794845 DOI: 10.1103/physrevlett.125.050403] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Accepted: 07/08/2020] [Indexed: 06/11/2023]
Abstract
In the current era of precision quantum many-body physics, one of the most scrutinized systems is the unitary limit of the nonrelativistic spin-1/2 Fermi gas, due to its simplicity and relevance for atomic, condensed matter, and nuclear physics. The thermodynamics of this strongly correlated system is determined by universal functions which, at high temperatures, are governed by universal virial coefficients b_{n} that capture the effects of the n-body system on the many-body dynamics. Currently, b_{2} and b_{3} are well understood, but the situation is less clear for b_{4}, and no predictions have been made for b_{5}. To answer these open questions, we implement a nonperturbative analytic approach based on the Trotter-Suzuki factorization of the imaginary-time evolution operator, using progressively finer temporal lattice spacings. By means of these factorizations and automated algebra codes, we obtain the interaction-induced change Δb_{n} from weak coupling to unitarity. At unitarity, we find that Δb_{3}=-0.356(4) in agreement with previous results, Δb_{4}=0.062(2), which is in agreement with all previous theoretical estimates but at odds with experimental determinations, and Δb_{5}=0.078(6), which is a prediction. We show the impact of those answers on the density equation of state and Tan contact, and trace their origin back to their polarized and unpolarized components.
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Affiliation(s)
- Y Hou
- Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - J E Drut
- Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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10
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Jensen S, Gilbreth CN, Alhassid Y. Contact in the Unitary Fermi Gas across the Superfluid Phase Transition. PHYSICAL REVIEW LETTERS 2020; 125:043402. [PMID: 32794813 DOI: 10.1103/physrevlett.125.043402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Accepted: 06/19/2020] [Indexed: 06/11/2023]
Abstract
A quantity known as the contact is a fundamental thermodynamic property of quantum many-body systems with short-range interactions. Determination of the temperature dependence of the contact for the unitary Fermi gas of infinite scattering length has been a major challenge, with different calculations yielding qualitatively different results. Here we use finite-temperature auxiliary-field quantum Monte Carlo (AFMC) methods on the lattice within the canonical ensemble to calculate the temperature dependence of the contact for the homogeneous spin-balanced unitary Fermi gas. We extrapolate to the continuum limit for 40, 66, and 114 particles, eliminating systematic errors due to finite-range effects. We observe a dramatic decrease in the contact as the superfluid critical temperature is approached from below, followed by a gradual weak decrease as the temperature increases in the normal phase. Our theoretical results are in excellent agreement with the most recent precision ultracold atomic gas experiments. We also present results for the energy as a function of temperature in the continuum limit.
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Affiliation(s)
- S Jensen
- Center for Theoretical Physics, Sloane Physics Laboratory, Yale University, New Haven, Connecticut 06520, USA
| | - C N Gilbreth
- Department of Physics, Central Washington University, Ellensburg, Washington 98926, USA
| | - Y Alhassid
- Center for Theoretical Physics, Sloane Physics Laboratory, Yale University, New Haven, Connecticut 06520, USA
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11
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Jensen S, Gilbreth CN, Alhassid Y. Pairing Correlations across the Superfluid Phase Transition in the Unitary Fermi Gas. PHYSICAL REVIEW LETTERS 2020; 124:090604. [PMID: 32202890 DOI: 10.1103/physrevlett.124.090604] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Revised: 06/17/2019] [Accepted: 01/17/2020] [Indexed: 06/10/2023]
Abstract
In the two-component Fermi gas with a contact interaction, a pseudogap regime can exist at temperatures between the superfluid critical temperature T_{c} and a temperature T^{*}>T_{c}. This regime is characterized by pairing correlations without superfluidity. However, in the unitary limit of infinite scattering length, the existence of this regime is still debated. To help address this, we have applied finite-temperature auxiliary-field quantum Monte Carlo (AFMC) methods to study the thermodynamics of the superfluid phase transition and signatures of the pseudogap in the spin-balanced homogeneous unitary Fermi gas. We present results at finite filling factor ν≃0.06 for the condensate fraction, an energy-staggering pairing gap, the spin susceptibility, and the heat capacity, and compare them to experimental data when available. In contrast to previous AFMC simulations, our model space consists of the complete first Brillouin zone of the lattice, and our calculations are performed in the canonical ensemble of fixed particle number. The canonical ensemble AFMC framework enables the calculation of a model-independent gap, providing direct information on pairing correlations without the need for numerical analytic continuation. We use finite-size scaling to estimate T_{c} at the corresponding filling factor. We find that the energy-staggering pairing gap vanishes above T_{c}, showing no pseudogap effects, and that the spin susceptibility shows a substantially reduced signature of a spin gap compared to previously reported AFMC simulations.
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Affiliation(s)
- S Jensen
- Center for Theoretical Physics, Sloane Physics Laboratory, Yale University, New Haven, Connecticut 06520, USA
| | - C N Gilbreth
- Institute for Nuclear Theory, Box 351550, University of Washington, Seattle, Washington 98195, USA
| | - Y Alhassid
- Center for Theoretical Physics, Sloane Physics Laboratory, Yale University, New Haven, Connecticut 06520, USA
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12
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Tajima H, Hatsuda T, van Wyk P, Ohashi Y. Superfluid Phase Transitions and Effects of Thermal Pairing Fluctuations in Asymmetric Nuclear Matter. Sci Rep 2019; 9:18477. [PMID: 31811255 PMCID: PMC6897924 DOI: 10.1038/s41598-019-54010-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Accepted: 10/30/2019] [Indexed: 11/09/2022] Open
Abstract
We investigate superfluid phase transitions of asymmetric nuclear matter at finite temperature (T) and density (ρ) with a low proton fraction (Yp ≤ 0.2), which is relevant to the inner crust and outer core of neutron stars. A strong-coupling theory developed for two-component atomic Fermi gases is generalized to the four-component case, and is applied to the system of spin-1/2 neutrons and protons. The phase shifts of neutron-neutron (nn), proton-proton (pp) and neutron-proton (np) interactions up to k = 2 fm-1 are described by multi-rank separable potentials. We show that the critical temperature [Formula: see text] of the neutron superfluidity at Yp = 0 agrees well with Monte Carlo data at low densities and takes a maximum value [Formula: see text]= 1.68 MeV at [Formula: see text] with ρ0 = 0.17 fm-3. Also, the critical temperature [Formula: see text] of the proton superconductivity for Yp ≤ 0.2 is substantially suppressed at low densities due to np-pairing fluctuations, and starts to dominate over [Formula: see text] only above [Formula: see text](0.77) for Yp = 0.1(0.2), and (iii) the deuteron condensation temperature [Formula: see text] is suppressed at Yp ≤ 0.2 due to a large mismatch of the two Fermi surfaces.
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Affiliation(s)
- Hiroyuki Tajima
- Quantum Hadron Physics Laboratory, RIKEN Nishina Center, Wako, Saitama, 351-0198, Japan.
| | - Tetsuo Hatsuda
- Quantum Hadron Physics Laboratory, RIKEN Nishina Center, Wako, Saitama, 351-0198, Japan.,Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS), RIKEN, Wako, Saitama, 351-0198, Japan
| | - Pieter van Wyk
- Department of Physics, Keio University, Hiyoshi, Kohoku-ku, Yokohama, 223-8522, Japan
| | - Yoji Ohashi
- Department of Physics, Keio University, Hiyoshi, Kohoku-ku, Yokohama, 223-8522, Japan
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13
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He YY, Shi H, Zhang S. Reaching the Continuum Limit in Finite-Temperature Ab Initio Field-Theory Computations in Many-Fermion Systems. PHYSICAL REVIEW LETTERS 2019; 123:136402. [PMID: 31697528 DOI: 10.1103/physrevlett.123.136402] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Indexed: 06/10/2023]
Abstract
Finite-temperature grand-canonical computations based on field theory are widely applied in areas including condensed matter physics, ultracold atomic gas systems, and the lattice gauge theory. However, these calculations have computational costs scaling as N_{s}^{3} with the size of the lattice or basis set, N_{s}. We report a new approach based on systematically controllable low-rank factorization that reduces the scaling of such computations to N_{s}N_{e}^{2}, where N_{e} is the average number of fermions in the system. In any realistic calculations aiming to describe the continuum limit, N_{s}/N_{e} is large and needs to be extrapolated effectively to infinity for convergence. The method thus fundamentally changes the prospect for finite-temperature many-body computations in correlated fermion systems. Its application, in combination with frameworks to control the sign or phase problem as needed, will provide a powerful tool in ab initio quantum chemistry and correlated electron materials. We demonstrate the method by computing exact properties of the two-dimensional Fermi gas with zero-range attractive interaction as a function of temperature in both the normal and superfluid states.
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Affiliation(s)
- Yuan-Yao He
- Center for Computational Quantum Physics, Flatiron Institute, New York, New York 10010, USA
- Department of Physics, College of William and Mary, Williamsburg, Virginia 23187, USA
| | - Hao Shi
- Center for Computational Quantum Physics, Flatiron Institute, New York, New York 10010, USA
| | - Shiwei Zhang
- Center for Computational Quantum Physics, Flatiron Institute, New York, New York 10010, USA
- Department of Physics, College of William and Mary, Williamsburg, Virginia 23187, USA
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14
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Mukherjee B, Patel PB, Yan Z, Fletcher RJ, Struck J, Zwierlein MW. Spectral Response and Contact of the Unitary Fermi Gas. PHYSICAL REVIEW LETTERS 2019; 122:203402. [PMID: 31172778 DOI: 10.1103/physrevlett.122.203402] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Indexed: 06/09/2023]
Abstract
We measure radio frequency (rf) spectra of the homogeneous unitary Fermi gas at temperatures ranging from the Boltzmann regime through quantum degeneracy and across the superfluid transition. For all temperatures, a single spectral peak is observed. Its position smoothly evolves from the bare atomic resonance in the Boltzmann regime to a frequency corresponding to nearly one Fermi energy at the lowest temperatures. At high temperatures, the peak width reflects the scattering rate of the atoms, while at low temperatures, the width is set by the size of fermion pairs. Above the superfluid transition, and approaching the quantum critical regime, the width increases linearly with temperature, indicating non-Fermi-liquid behavior. From the wings of the rf spectra, we obtain the contact, quantifying the strength of short-range pair correlations. We find that the contact rapidly increases as the gas is cooled below the superfluid transition.
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Affiliation(s)
- Biswaroop Mukherjee
- MIT-Harvard Center for Ultracold Atoms, Research Laboratory of Electronics, and Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Parth B Patel
- MIT-Harvard Center for Ultracold Atoms, Research Laboratory of Electronics, and Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Zhenjie Yan
- MIT-Harvard Center for Ultracold Atoms, Research Laboratory of Electronics, and Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Richard J Fletcher
- MIT-Harvard Center for Ultracold Atoms, Research Laboratory of Electronics, and Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Julian Struck
- MIT-Harvard Center for Ultracold Atoms, Research Laboratory of Electronics, and Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- Département de Physique, Ecole Normale Supérieure / PSL Research University, CNRS, 24 rue Lhomond, 75005 Paris, France
| | - Martin W Zwierlein
- MIT-Harvard Center for Ultracold Atoms, Research Laboratory of Electronics, and Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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15
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Murthy PA, Neidig M, Klemt R, Bayha L, Boettcher I, Enss T, Holten M, Zürn G, Preiss PM, Jochim S. High-temperature pairing in a strongly interacting two-dimensional Fermi gas. Science 2018; 359:452-455. [DOI: 10.1126/science.aan5950] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 12/06/2017] [Indexed: 11/02/2022]
Affiliation(s)
| | - Mathias Neidig
- Physics Institute, Heidelberg University, Heidelberg, Germany
| | - Ralf Klemt
- Physics Institute, Heidelberg University, Heidelberg, Germany
| | - Luca Bayha
- Physics Institute, Heidelberg University, Heidelberg, Germany
| | - Igor Boettcher
- Department of Physics, Simon Fraser University, Burnaby, BC, Canada
| | - Tilman Enss
- Institute for Theoretical Physics, Heidelberg University, Heidelberg, Germany
| | - Marvin Holten
- Physics Institute, Heidelberg University, Heidelberg, Germany
| | - Gerhard Zürn
- Physics Institute, Heidelberg University, Heidelberg, Germany
| | | | - Selim Jochim
- Physics Institute, Heidelberg University, Heidelberg, Germany
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