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Yuheng Zhang - One of the best experts on this subject based on the ideXlab platform.
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Magnetic Polaron conduction in the colossal magnetoresistance material fe 1 x cd x cr 2 s 4
Physical Review B, 2004Co-Authors: Zhaorong Yang, Shun Tan, Xinyu Bao, Yuheng ZhangAbstract:The magnetotransport properties of the spinel ${\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Cd}}_{x}{\mathrm{Cr}}_{2}{\mathrm{S}}_{4}$ have been studied. We found that the Magnetic Polarons dominate the conduction at temperatures above the Curie temperature ${\mathrm{T}}_{c}.$ Upon substitution of Fe by Cd, the carrier density decreases, and the magnetoresistance increases. As a result, the Magnetic Polarons become more stable, in agreement with the theoretical predictions of Majumdar and Littlewood for the magnetoresistance in low carrier density ferromagnets. The evolution of Magnetic Polarons in ${\mathrm{CdCr}}_{2}{\mathrm{S}}_{4}$ has been studied with electron spin resonance (ESR) measurements. As the temperature increases, the peak-to-peak linewidth $\ensuremath{\Delta}{H}_{\mathrm{pp}}$ decreases in a broad temperature range, providing direct evidence for the existence of Magnetic Polarons. The analysis of the ESR spectra reveals the existence of two temperature scales, which are related to the evolution of the Magnetic Polarons. The first temperature, denoted as ${T}_{p},$ corresponds to the formation of Magnetic Polarons. The second temperature, denoted as ${T}^{*},$ can be related to the temperature where correlations among the Magnetic Polarons occur.
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Magnetic Polaron conductivity in fecr2s4 with the colossal magnetoresistance effect
Physical Review B, 2000Co-Authors: Zhaorong Yang, Shun Tan, Zhiwen Chen, Yuheng ZhangAbstract:The Magnetic and electrical transport properties of the colossal magnetoresistance material FeCr2S4 are studied. Low-temperature thermoelectric power and resistivity measurements indicate that Magnetic Polarons dominate the conduction behavior at temperatures above T-c(onset). The temperature dependence of the susceptibility chi, measured from 4.2 to 400 K, suggests that FeCr2S4 is ferriMagnetic. Then the micromagnetism of FeCr2S4 is further investigated by electron-spin-resonance measurements from 100 to 290 K, which reveal that the paraMagnetic-ferroMagnetic transition is incomplete and that a paraMagnetic phase coexists with a ferriMagnetic phase in a certain temperature range below T-c(onset). Accompanying the paraMagnetic-ferriMagnetic phase transition, Magnetic Polarons may delocalize gradually into the naked carriers. The resistivity in the presented temperature range can be described in terms of the two-fluid model concerning the coexistence of Magnetic Polarons and naked carriers.
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Magnetic Polaron conductivity in fecr 2 s 4 with the colossal magnetoresistance effect
Physical Review B, 2000Co-Authors: Zhaorong Yang, Shun Tan, Zhiwen Chen, Yuheng ZhangAbstract:The Magnetic and electrical transport properties of the colossal magnetoresistance material ${\mathrm{FeCr}}_{2}{\mathrm{S}}_{4}$ are studied. Low-temperature thermoelectric power and resistivity measurements indicate that Magnetic Polarons dominate the conduction behavior at temperatures above ${T}_{c}^{\mathrm{onset}}.$ The temperature dependence of the susceptibility \ensuremath{\chi}, measured from 4.2 to 400 K, suggests that ${\mathrm{FeCr}}_{2}{\mathrm{S}}_{4}$ is ferriMagnetic. Then the micromagnetism of ${\mathrm{FeCr}}_{2}{\mathrm{S}}_{4}$ is further investigated by electron-spin-resonance measurements from 100 to 290 K, which reveal that the paraMagnetic-ferriMagnetic transition is incomplete and that a paraMagnetic phase coexists with a ferriMagnetic phase in a certain temperature range below ${T}_{c}^{\mathrm{onset}}.$ Accompanying the paraMagnetic-ferriMagnetic phase transition, Magnetic Polarons may delocalize gradually into the naked carriers. The resistivity in the presented temperature range can be described in terms of the two-fluid model concerning the coexistence of Magnetic Polarons and naked carriers.
Annabelle Bohrdt - One of the best experts on this subject based on the ideXlab platform.
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coupling a mobile hole to an antiferroMagnetic spin background transient dynamics of a Magnetic Polaron
Physical Review X, 2021Co-Authors: Lev Kendrick, Eugene Demler, Annabelle Bohrdt, Fabian Grusdt, Christie S Chiu, Justus Bruggenjurgen, Daniel Greif, Martin Lebrat, Markus GreinerAbstract:Using an optical lattice of cold atoms, quantum simulation of a single electron hole added to an antiferromagnet reveals how the hole alters the spin environment and how the spins slow down the hole.
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dynamical formation of a Magnetic Polaron in a two dimensional quantum antiferromagnet
New Journal of Physics, 2020Co-Authors: Annabelle Bohrdt, Fabian Grusdt, Michael KnapAbstract:We numerically study the real-time dynamics of a single hole created in the $t-J$ model on a square lattice. Initially, the hole spreads ballistically with a velocity proportional to the hopping matrix element. At intermediate to long times, the dimensionality as well as the spin background determine the hole dynamics. A hole created in the ground state of a two dimensional quantum antiferromagnet propagates again ballistically at long times but with a velocity proportional to the spin exchange coupling, showing the formation of a Magnetic Polaron. We provide an intuitive explanation of this dynamics in terms of a parton construction, which leads to a good quantitative agreement with the numerical simulations. In the limit of infinite temperature and no spin exchange couplings, the dynamics can be approximated by a quantum random walk on the Bethe lattice. Adding Ising interactions corresponds to an effective disordered potential, which can dramatically slow down the hole propagation, consistent with subdiffusive dynamics.
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coupling a mobile hole to an antiferroMagnetic spin background transient dynamics of a Magnetic Polaron
arXiv: Quantum Gases, 2020Co-Authors: Lev Kendrick, Eugene Demler, Annabelle Bohrdt, Fabian Grusdt, Christie S Chiu, Justus Bruggenjurgen, Daniel Greif, Martin Lebrat, Markus GreinerAbstract:Understanding the interplay between charge and spin and its effects on transport is a ubiquitous challenge in quantum many-body systems. In the Fermi-Hubbard model, this interplay is thought to give rise to Magnetic Polarons, whose dynamics may explain emergent properties of quantum materials such as high-temperature superconductivity. In this work, we use a cold-atom quantum simulator to directly observe the formation dynamics and subsequent spreading of individual Magnetic Polarons. Measuring the density- and spin-resolved evolution of a single hole in a 2D Hubbard insulator with short-range antiferroMagnetic correlations reveals fast initial delocalization and a dressing of the spin background, indicating Polaron formation. At long times, we find that dynamics are slowed down by the spin exchange time, and they are compatible with a Polaronic model with strong density and spin coupling. Our work enables the study of out-of-equilibrium emergent phenomena in the Fermi-Hubbard model, one dopant at a time.
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microscopic spinon chargon theory of Magnetic Polarons in the t j model
Physical Review B, 2019Co-Authors: Fabian Grusdt, Annabelle Bohrdt, Eugene DemlerAbstract:The interplay of spin and charge degrees of freedom, introduced by doping mobile holes into a Mott insulator with strong antiferroMagnetic (AFM) correlations, is at the heart of strongly correlated matter such as high-${T}_{c}$ cuprate superconductors. Here, we capture this interplay in the strong coupling regime and propose a trial wave function of mobile holes in an AFM. Our method provides a microscopic justification for a class of theories which describe doped holes moving in an AFM environment as mesonlike bound states of spinons and chargons. We discuss a model of such bound states from the perspective of geometric strings, which describe a fluctuating lattice geometry introduced by the fast motion of the chargon, relative to the spinon. This is demonstrated to give rise to short-range hidden string order, signatures of which have recently been revealed by ultracold atom experiments at elevated temperatures. We present evidence for such short-range hidden string correlations also at zero temperature by performing numerical density-matrix renormalization-group simulations. To test our microscopic approach, we calculate the ground-state energy and dispersion relation of a hole in an AFM, as well as the Magnetic Polaron radius, and obtain good quantitative agreement with advanced numerical simulations at strong coupling. We discuss extensions of our analysis to systems without long-range AFM order to systems with short-range Magnetic correlations.
Fabian Grusdt - One of the best experts on this subject based on the ideXlab platform.
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coupling a mobile hole to an antiferroMagnetic spin background transient dynamics of a Magnetic Polaron
Physical Review X, 2021Co-Authors: Lev Kendrick, Eugene Demler, Annabelle Bohrdt, Fabian Grusdt, Christie S Chiu, Justus Bruggenjurgen, Daniel Greif, Martin Lebrat, Markus GreinerAbstract:Using an optical lattice of cold atoms, quantum simulation of a single electron hole added to an antiferromagnet reveals how the hole alters the spin environment and how the spins slow down the hole.
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dynamical formation of a Magnetic Polaron in a two dimensional quantum antiferromagnet
New Journal of Physics, 2020Co-Authors: Annabelle Bohrdt, Fabian Grusdt, Michael KnapAbstract:We numerically study the real-time dynamics of a single hole created in the $t-J$ model on a square lattice. Initially, the hole spreads ballistically with a velocity proportional to the hopping matrix element. At intermediate to long times, the dimensionality as well as the spin background determine the hole dynamics. A hole created in the ground state of a two dimensional quantum antiferromagnet propagates again ballistically at long times but with a velocity proportional to the spin exchange coupling, showing the formation of a Magnetic Polaron. We provide an intuitive explanation of this dynamics in terms of a parton construction, which leads to a good quantitative agreement with the numerical simulations. In the limit of infinite temperature and no spin exchange couplings, the dynamics can be approximated by a quantum random walk on the Bethe lattice. Adding Ising interactions corresponds to an effective disordered potential, which can dramatically slow down the hole propagation, consistent with subdiffusive dynamics.
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coupling a mobile hole to an antiferroMagnetic spin background transient dynamics of a Magnetic Polaron
arXiv: Quantum Gases, 2020Co-Authors: Lev Kendrick, Eugene Demler, Annabelle Bohrdt, Fabian Grusdt, Christie S Chiu, Justus Bruggenjurgen, Daniel Greif, Martin Lebrat, Markus GreinerAbstract:Understanding the interplay between charge and spin and its effects on transport is a ubiquitous challenge in quantum many-body systems. In the Fermi-Hubbard model, this interplay is thought to give rise to Magnetic Polarons, whose dynamics may explain emergent properties of quantum materials such as high-temperature superconductivity. In this work, we use a cold-atom quantum simulator to directly observe the formation dynamics and subsequent spreading of individual Magnetic Polarons. Measuring the density- and spin-resolved evolution of a single hole in a 2D Hubbard insulator with short-range antiferroMagnetic correlations reveals fast initial delocalization and a dressing of the spin background, indicating Polaron formation. At long times, we find that dynamics are slowed down by the spin exchange time, and they are compatible with a Polaronic model with strong density and spin coupling. Our work enables the study of out-of-equilibrium emergent phenomena in the Fermi-Hubbard model, one dopant at a time.
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microscopic spinon chargon theory of Magnetic Polarons in the t j model
Physical Review B, 2019Co-Authors: Fabian Grusdt, Annabelle Bohrdt, Eugene DemlerAbstract:The interplay of spin and charge degrees of freedom, introduced by doping mobile holes into a Mott insulator with strong antiferroMagnetic (AFM) correlations, is at the heart of strongly correlated matter such as high-${T}_{c}$ cuprate superconductors. Here, we capture this interplay in the strong coupling regime and propose a trial wave function of mobile holes in an AFM. Our method provides a microscopic justification for a class of theories which describe doped holes moving in an AFM environment as mesonlike bound states of spinons and chargons. We discuss a model of such bound states from the perspective of geometric strings, which describe a fluctuating lattice geometry introduced by the fast motion of the chargon, relative to the spinon. This is demonstrated to give rise to short-range hidden string order, signatures of which have recently been revealed by ultracold atom experiments at elevated temperatures. We present evidence for such short-range hidden string correlations also at zero temperature by performing numerical density-matrix renormalization-group simulations. To test our microscopic approach, we calculate the ground-state energy and dispersion relation of a hole in an AFM, as well as the Magnetic Polaron radius, and obtain good quantitative agreement with advanced numerical simulations at strong coupling. We discuss extensions of our analysis to systems without long-range AFM order to systems with short-range Magnetic correlations.
D R Yakovlev - One of the best experts on this subject based on the ideXlab platform.
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Magnetic Polaron on dangling bond spins in cdse colloidal nanocrystals
Nature Nanotechnology, 2017Co-Authors: Louis Biadala, D R Yakovlev, Elena V Shornikova, A V Rodina, Benjamin Siebers, Tangi Aubert, Michel Nasilowski, Zeger HensAbstract:Non-Magnetic colloidal nanostructures can demonstrate Magnetic properties typical for diluted Magnetic semiconductors because the spins of dangling bonds at their surface can act as the localized spins of Magnetic ions. Here we report the observation of dangling-bond Magnetic Polarons (DBMPs) in 2.8-nm diameter CdSe colloidal nanocrystals (NCs). The DBMP binding energy of 7 meV is measured from the spectral shift of the emission lines under selective laser excitation. The Polaron formation at low temperatures occurs by optical orientation of the dangling-bond spins (DBSs) that result from dangling-bond-assisted radiative recombination of spin-forbidden dark excitons. Modelling of the temperature dependence of the DBMP-binding energy and emission intensity shows that the DBMP is composed of a dark exciton and about 60 DBSs. The exchange integral of one DBS with the electron confined in the NC is ∼0.12 meV. NonMagnetic colloidal nanocrystals demonstrate Magnetic properties due to spins of dangling bonds at their surface resulting in formation of dangling-bond Magnetic Polarons.
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exciton Magnetic Polaron in cdmnse cdmgse quantum wells
Physica Status Solidi B-basic Solid State Physics, 2010Co-Authors: T Godde, I I Reshina, S V Ivanov, I A Akimov, D R Yakovlev, M BayerAbstract:We study exciton Magnetic Polaron (EMP) formation in (Cd,Mn)Se/(Cd,Mg)Se diluted Magnetic semiconductor quantum wells (QWs) using time-resolved photoluminescence (PL). Magnetic field dependence of the transients allows us to separate the non-Magnetic and Magnetic contributions of the exciton localization. We find binding energy of 18 meV and formation time of 500 ps for the EMP. We propose that long Polaron formation time is related to auto-localization process, accompanied with the squeezing of the heavy-hole envelope wave function. This conclusion is supported by a strong reduction of the exciton radiative lifetime from 600 to 200 ps with increase of Magnetic field.
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two dimensional exciton Magnetic Polaron in cdte cd1 xmnxte quantum well structures
Solid State Communications, 1992Co-Authors: D R Yakovlev, W Ossau, G Landwehr, R N Bicknelltassius, A Waag, S Schmeusser, I N UraltsevAbstract:Abstract We report the first investigation of two-dimensional Magnetic Polarons formed from excitons localized in very thin nonMagnetic CdTe quantum wells confined by Cd1−xMnxTe diluted-Magnetic-semiconductor barriers. Analysis of the Stokes shift of the exciton luminescence peak under resonance excitation, which is a dramatically decreasing function of temperature and Magnetic field, allows us to determine the Magnetic Polaron energy. The Polaron energy measured as a function of quantum well width is found to be 25 meV in a 6 A thick quantum well and to vanish in wells thicker than 30 A.
Zhaorong Yang - One of the best experts on this subject based on the ideXlab platform.
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Magnetic Polaron conduction in the colossal magnetoresistance material fe 1 x cd x cr 2 s 4
Physical Review B, 2004Co-Authors: Zhaorong Yang, Shun Tan, Xinyu Bao, Yuheng ZhangAbstract:The magnetotransport properties of the spinel ${\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Cd}}_{x}{\mathrm{Cr}}_{2}{\mathrm{S}}_{4}$ have been studied. We found that the Magnetic Polarons dominate the conduction at temperatures above the Curie temperature ${\mathrm{T}}_{c}.$ Upon substitution of Fe by Cd, the carrier density decreases, and the magnetoresistance increases. As a result, the Magnetic Polarons become more stable, in agreement with the theoretical predictions of Majumdar and Littlewood for the magnetoresistance in low carrier density ferromagnets. The evolution of Magnetic Polarons in ${\mathrm{CdCr}}_{2}{\mathrm{S}}_{4}$ has been studied with electron spin resonance (ESR) measurements. As the temperature increases, the peak-to-peak linewidth $\ensuremath{\Delta}{H}_{\mathrm{pp}}$ decreases in a broad temperature range, providing direct evidence for the existence of Magnetic Polarons. The analysis of the ESR spectra reveals the existence of two temperature scales, which are related to the evolution of the Magnetic Polarons. The first temperature, denoted as ${T}_{p},$ corresponds to the formation of Magnetic Polarons. The second temperature, denoted as ${T}^{*},$ can be related to the temperature where correlations among the Magnetic Polarons occur.
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Magnetic Polaron conductivity in fecr2s4 with the colossal magnetoresistance effect
Physical Review B, 2000Co-Authors: Zhaorong Yang, Shun Tan, Zhiwen Chen, Yuheng ZhangAbstract:The Magnetic and electrical transport properties of the colossal magnetoresistance material FeCr2S4 are studied. Low-temperature thermoelectric power and resistivity measurements indicate that Magnetic Polarons dominate the conduction behavior at temperatures above T-c(onset). The temperature dependence of the susceptibility chi, measured from 4.2 to 400 K, suggests that FeCr2S4 is ferriMagnetic. Then the micromagnetism of FeCr2S4 is further investigated by electron-spin-resonance measurements from 100 to 290 K, which reveal that the paraMagnetic-ferroMagnetic transition is incomplete and that a paraMagnetic phase coexists with a ferriMagnetic phase in a certain temperature range below T-c(onset). Accompanying the paraMagnetic-ferriMagnetic phase transition, Magnetic Polarons may delocalize gradually into the naked carriers. The resistivity in the presented temperature range can be described in terms of the two-fluid model concerning the coexistence of Magnetic Polarons and naked carriers.
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Magnetic Polaron conductivity in fecr 2 s 4 with the colossal magnetoresistance effect
Physical Review B, 2000Co-Authors: Zhaorong Yang, Shun Tan, Zhiwen Chen, Yuheng ZhangAbstract:The Magnetic and electrical transport properties of the colossal magnetoresistance material ${\mathrm{FeCr}}_{2}{\mathrm{S}}_{4}$ are studied. Low-temperature thermoelectric power and resistivity measurements indicate that Magnetic Polarons dominate the conduction behavior at temperatures above ${T}_{c}^{\mathrm{onset}}.$ The temperature dependence of the susceptibility \ensuremath{\chi}, measured from 4.2 to 400 K, suggests that ${\mathrm{FeCr}}_{2}{\mathrm{S}}_{4}$ is ferriMagnetic. Then the micromagnetism of ${\mathrm{FeCr}}_{2}{\mathrm{S}}_{4}$ is further investigated by electron-spin-resonance measurements from 100 to 290 K, which reveal that the paraMagnetic-ferriMagnetic transition is incomplete and that a paraMagnetic phase coexists with a ferriMagnetic phase in a certain temperature range below ${T}_{c}^{\mathrm{onset}}.$ Accompanying the paraMagnetic-ferriMagnetic phase transition, Magnetic Polarons may delocalize gradually into the naked carriers. The resistivity in the presented temperature range can be described in terms of the two-fluid model concerning the coexistence of Magnetic Polarons and naked carriers.