Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Results in Physics

Magnetic impurity states of a Fermi system in a local magnetic field

Bin‐Zhou Mi, Qiang Gu

Published Apr 23, 2024• 1 citation
Publisher

Abstract

The ultracold atomic Fermi gas provides a flexible and controllable experimental platform for exploring magnetic impurity states. In this study, we theoretically examine the magnetic impurity states in a Fermi system with spin-1/2 and spin-3/2 under a local magnetic field. Firstly, the spin-1/2 impurity system contains three types of magnetic solutions. One type magnetic solution with higher energy can be regarded as the result of induced magnetization of a trivial solution, while the other two types magnetic solutions with lower energy can be understood as the results of Zeeman splitting of nontrivial solutions with double degeneracy. Notably, the magnetic solution corresponding to the spin state parallel to the Zeeman magnetic field is always the most stable in terms of the energy. Secondly, we extend the idea of studying spin-1/2 impurity to spin-3/2 impurity, where the half-filled state of impurity atoms is calculated. We found that four types of magnetic solutions at zero magnetic field were split into four, six, four, and twelve new magnetic solutions in the presence of a Zeeman magnetic field, respectively. We obtained that the magnetic solution corresponding to the spin state parallel to the magnetic field is the most stable, and its energy is lower than that of the corresponding magnetic solution at zero magnetic field. Therefore, the introduction of a local magnetic field is beneficial for the formation of magnetic impurity states. Finally, the calculated data illustrate that the Anderson impurity model we adopt exhibits invariance under the combined transformations of spin-flip and particle-hole.

DOI
10.1016/j.rinp.2024.107693

Related papers

Formation of localized magnetic states in a large-spin Fermi system

Bin‐Zhou Mi, Qiang Gu

We extend the Anderson impurity model to a large-spin Fermi system with spin $f=\frac{3}{2}$, stimulated by the realization of large-spin ultracold Fermi atoms. The condition required for the spontaneous formation of local magnetic moments is examined and the ground-state mean-field magnetic phase diagram is explored carefully. We find that the spin-$\frac{3}{2}$ Fermi system involves magnetic phase regions I, II, and III that correspond to one, two, and three particle/hole occupation, respectively. In addition, it is observed that all the three magnetic phases have fourfold-degenerate ground states. Finally, the phase transition between the three phases seems to be of the first order.

arXiv:1905.05398•Physical review. B./Physical review. B•May 9, 2019•5 citations

Formation of magnetic impurities and pair-breaking effect in a superfluid Fermi gas

Yoji Ohashi

We theoretically investigate the introduction of magnetic impurities into a superfluid Fermi gas. In the presence of a population imbalance (${N}_{\ensuremath{\uparrow}}>{N}_{\ensuremath{\downarrow}}$, where ${N}_{\ensuremath{\sigma}}$ is the number of Fermi atoms with pseudospin $\ensuremath{\sigma}=\ensuremath{\uparrow},\ensuremath{\downarrow}$), we show that nonmagnetic potential scatterers embedded in the system are magnetized in the sense that some of the excess spin-$\ensuremath{\uparrow}$ atoms are localized around them. They destroy the superfluid order parameter around them, as in the case of the magnetic impurity effect discussed in the superconductivity literature. This pair-breaking effect naturally leads to localized excited states below the superfluid excitation gap. To confirm our idea in a simple manner, we consider an attractive Fermi-Hubbard model within the mean-field theory at $T=0$. We determine consistent superfluid properties around a nonmagnetic impurity, such as the superfluid order parameter, local population imbalance, as well as the single-particle density of states, in the presence of a population imbalance. Since competition between superconductivity and magnetism is one of the most fundamental problems in condensed-matter physics, our results would be useful for the study of this important issue in cold Fermi gases.

arXiv:1103.1942•Physical Review A•Jun 10, 2011•12 citations

Elementary excitations of a two-dimensional Ising ferromagnet in a transverse magnetic field in the presence of impurities

Yu. G. Okladnoy, V. M. Tsukernik

The influence of a magnetic impurity on the elementary excitation spectrum of a two-dimensional Ising ferromagnet is investigated in a low transverse magnetic field. It is shown that in the case of a “ferromagnetic” impurity in a matrix of spin 1/2, from one to three local energy levels can be split off from the lower edge of the continuous spectrum of one-magnon states where the conditions for their existence impose quite strict constraints on the spin-Hamiltonian parameters. Three distinct spin configurations can be realized in the presence of an “antiferromagnetic” impurity in the crystal in the ground state. Single-magnon states of a ferromagnet are considered for those values of the spin-Hamiltonian parameters when two of them are realized. It is shown that from one to six local levels above or below the continuous spectrum band can appear, and their distance from the band edge can substantially exceed its width. Quasilocal energy levels originating within the continuous spectrum of the single-magnon states are also investigated.

Soviet Journal of Low Temperature Physics•Aug 1, 1976•0 citations

Field-induced ferromagnetic phase transition in two-dimensional Fermi systems with magnetic dipole-dipole interaction

G. H. Bordbar, Fatemeh Pouresmaeeli, A. Poostforush

Magnetic properties of two-dimensional (2D) spin-polarized Fermi gas with dipole-dipole interaction are studied in the presence of external magnetic field at zero temperature. Within perturbation theory and the second quantization formalism, the total energy is explicitly obtained as a function of three dimensionless parameters: the spin polarization, dipolar coupling, and Zeeman parameters. We examine the effects of these agents on the magnetic properties of 2D Fermi gas. The results show that an induced ferromagnetic phase transition is observed only for adequately large values of magnetic field. This paper offers two controllable factors to change the spin polarization of the system.

arXiv:1812.02913•Physical Review A•Aug 31, 2018•0 citations

Inducing spin-order with an impurity: phase diagram of the magnetic Bose polaron

S. I. Mistakidis, Georgios M. Koutentakis, Fabian Grusdt +2 more

Abstract We investigate the formation of magnetic Bose polaron, an impurity atom dressed by spin-wave excitations, in a one-dimensional spinor Bose gas. Within an effective potential model, the impurity is strongly confined by the host excitations which can even overcome the impurity-medium repulsion leading to a self-localized quasi-particle state. The phase diagram of the attractive and self-bound repulsive magnetic polaron, repulsive non-magnetic (Fröhlich-type) polaron and impurity-medium phase-separation regimes is explored with respect to the Rabi-coupling between the spin components, spin–spin interactions and impurity-medium coupling. The residue of such magnetic polarons decreases substantially in both strong attractive and repulsive branches with strong impurity-spin interactions, illustrating significant dressing of the impurity. The impurity can be used to probe and maneuver the spin polarization of the magnetic medium while suppressing ferromagnetic spin–spin correlations. It is shown that mean-field theory fails as the spinor gas approaches immiscibility since the generated spin-wave excitations are prominent. Our findings illustrate that impurities can be utilized to generate controllable spin–spin correlations and magnetic polaron states which can be realized with current cold atom setups.

arXiv:2204.10960•New Journal of Physics•Jul 22, 2022•17 citations

Magnetic Phase Transitions in One-Dimensional Strongly Attractive Three-Component Ultracold Fermions

Xin Guan, Murray T. Batchelor, Chaohong Lee +1 more

We investigate the nature of trions, pairing, and quantum phase transitions in one-dimensional strongly attractive three-component ultracold fermions in external fields. Exact results for the ground-state energy, critical fields, magnetization and phase diagrams are obtained analytically from the Bethe ansatz solutions. Driven by Zeeman splitting, the system shows exotic phases of trions, bound pairs, a normal Fermi liquid, and four mixtures of these states. Particularly, a smooth phase transition from a trionic phase into a pairing phase occurs as the highest hyperfine level separates from the two lower energy levels. In contrast, there is a smooth phase transition from the trionic phase into a normal Fermi liquid as the lowest level separates from the two higher levels.

arXiv:0709.1763•Physical Review Letters•May 19, 2008•45 citations
The ultracold atomic Fermi gas provides a flexible and controllable experimental platform for exploring magnetic impurity states. In this study, we theoretically examine the magnetic impurity states in a Fermi system with spin-1/2 and spin-3/2 under a local magnetic field. Firstly, the spin-1/2 impurity system contains three types of magnetic solutions. One type magnetic solution with higher energy can be regarded as the result of induced magnetization of a trivial solution, while the other two types magnetic solutions with lower energy can be understood as the results of Zeeman splitting of nontrivial solutions with double degeneracy. Notably, the magnetic solution corresponding to the spin state parallel to the Zeeman magnetic field is always the most stable in terms of the energy. Secondly, we extend the idea of studying spin-1/2 impurity to spin-3/2 impurity, where the half-filled state of impurity atoms is calculated. We found that four types of magnetic solutions at zero magnetic field were split into four, six, four, and twelve new magnetic solutions in the presence of a Zeeman magnetic field, respectively. We obtained that the magnetic solution corresponding to the spin state parallel to the magnetic field is the most stable, and its energy is lower than that of the corresponding magnetic solution at zero magnetic field. Therefore, the introduction of a local magnetic field is beneficial for the formation of magnetic impurity states. Finally, the calculated data illustrate that the Anderson impurity model we adopt exhibits invariance under the combined transformations of spin-flip and particle-hole.
We extend the Anderson impurity model to a large-spin Fermi system with spin f=32f=\frac{3}{2}f=23​, stimulated by the realization of large-spin ultracold Fermi atoms. The condition required for the spontaneous formation of local magnetic moments is examined and the ground-state mean-field magnetic phase diagram is explored carefully. We find that the spin-32\frac{3}{2}23​ Fermi system involves magnetic phase regions I, II, and III that correspond to one, two, and three particle/hole occupation, respectively. In addition, it is observed that all the three magnetic phases have fourfold-degenerate ground states. Finally, the phase transition between the three phases seems to be of the first order.
We theoretically investigate the introduction of magnetic impurities into a superfluid Fermi gas. In the presence of a population imbalance (${N}_{\ensuremath{\uparrow}}>{N}_{\ensuremath{\downarrow}}$, where ${N}_{\ensuremath{\sigma}}$ is the number of Fermi atoms with pseudospin $\ensuremath{\sigma}=\ensuremath{\uparrow},\ensuremath{\downarrow}$), we show that nonmagnetic potential scatterers embedded in the system are magnetized in the sense that some of the excess spin-$\ensuremath{\uparrow}$ atoms are localized around them. They destroy the superfluid order parameter around them, as in the case of the magnetic impurity effect discussed in the superconductivity literature. This pair-breaking effect naturally leads to localized excited states below the superfluid excitation gap. To confirm our idea in a simple manner, we consider an attractive Fermi-Hubbard model within the mean-field theory at T=0T=0T=0. We determine consistent superfluid properties around a nonmagnetic impurity, such as the superfluid order parameter, local population imbalance, as well as the single-particle density of states, in the presence of a population imbalance. Since competition between superconductivity and magnetism is one of the most fundamental problems in condensed-matter physics, our results would be useful for the study of this important issue in cold Fermi gases.
The influence of a magnetic impurity on the elementary excitation spectrum of a two-dimensional Ising ferromagnet is investigated in a low transverse magnetic field. It is shown that in the case of a “ferromagnetic” impurity in a matrix of spin 1/2, from one to three local energy levels can be split off from the lower edge of the continuous spectrum of one-magnon states where the conditions for their existence impose quite strict constraints on the spin-Hamiltonian parameters. Three distinct spin configurations can be realized in the presence of an “antiferromagnetic” impurity in the crystal in the ground state. Single-magnon states of a ferromagnet are considered for those values of the spin-Hamiltonian parameters when two of them are realized. It is shown that from one to six local levels above or below the continuous spectrum band can appear, and their distance from the band edge can substantially exceed its width. Quasilocal energy levels originating within the continuous spectrum of the single-magnon states are also investigated.
Magnetic properties of two-dimensional (2D) spin-polarized Fermi gas with dipole-dipole interaction are studied in the presence of external magnetic field at zero temperature. Within perturbation theory and the second quantization formalism, the total energy is explicitly obtained as a function of three dimensionless parameters: the spin polarization, dipolar coupling, and Zeeman parameters. We examine the effects of these agents on the magnetic properties of 2D Fermi gas. The results show that an induced ferromagnetic phase transition is observed only for adequately large values of magnetic field. This paper offers two controllable factors to change the spin polarization of the system.
Abstract We investigate the formation of magnetic Bose polaron, an impurity atom dressed by spin-wave excitations, in a one-dimensional spinor Bose gas. Within an effective potential model, the impurity is strongly confined by the host excitations which can even overcome the impurity-medium repulsion leading to a self-localized quasi-particle state. The phase diagram of the attractive and self-bound repulsive magnetic polaron, repulsive non-magnetic (Fröhlich-type) polaron and impurity-medium phase-separation regimes is explored with respect to the Rabi-coupling between the spin components, spin–spin interactions and impurity-medium coupling. The residue of such magnetic polarons decreases substantially in both strong attractive and repulsive branches with strong impurity-spin interactions, illustrating significant dressing of the impurity. The impurity can be used to probe and maneuver the spin polarization of the magnetic medium while suppressing ferromagnetic spin–spin correlations. It is shown that mean-field theory fails as the spinor gas approaches immiscibility since the generated spin-wave excitations are prominent. Our findings illustrate that impurities can be utilized to generate controllable spin–spin correlations and magnetic polaron states which can be realized with current cold atom setups.
We investigate the nature of trions, pairing, and quantum phase transitions in one-dimensional strongly attractive three-component ultracold fermions in external fields. Exact results for the ground-state energy, critical fields, magnetization and phase diagrams are obtained analytically from the Bethe ansatz solutions. Driven by Zeeman splitting, the system shows exotic phases of trions, bound pairs, a normal Fermi liquid, and four mixtures of these states. Particularly, a smooth phase transition from a trionic phase into a pairing phase occurs as the highest hyperfine level separates from the two lower energy levels. In contrast, there is a smooth phase transition from the trionic phase into a normal Fermi liquid as the lowest level separates from the two higher levels.