The transition energies, wavelengths and dipole oscillator strengths of 1s22p-1s2nd (3≤n≤9) for Mn22+ ion are calculated. The fine structure splittings of 1s2nd (n≤9) states for this ion are also evaluated. In calc...The transition energies, wavelengths and dipole oscillator strengths of 1s22p-1s2nd (3≤n≤9) for Mn22+ ion are calculated. The fine structure splittings of 1s2nd (n≤9) states for this ion are also evaluated. In calculating energy, the higher-order relativistic contribution is estimated under a hydrogenic approximation. The quantum defect of Rydberg series 1s2nd is determined according to the quantum defect theory. The results obtained in this paper excellently agree with the experi-mental data available in literatures.展开更多
The transition energies, wavelengths and dipole oscillator strengths of 1s^22p-1s^2nd （3 ≤ n ≤ 9） for Cr^21＋ ion are calculated. The fine structure splittings of 1s^2nd （n ≤ 9） states for this ion are also cal...The transition energies, wavelengths and dipole oscillator strengths of 1s^22p-1s^2nd （3 ≤ n ≤ 9） for Cr^21＋ ion are calculated. The fine structure splittings of 1s^2nd （n ≤ 9） states for this ion are also calculated. In calculating energy, we have estimated the higher-order relativistic contribution under a hydrogenic approximation. The quantum defect of Rydberg series 1s^2nd is determined according to the quantum defect theory. The results obtained in this paper excellently agree with the experimental data available in the literature. Combining the quantum defect theory with the discrete oscillator strengths, the discrete oscillator strengths for the transitions from initial state 1s^22p to highly excited 1s^2nd states （n ≥ 10） and the oscillator strength density corresponding to the bound-free transitions are obtained.展开更多
Assuming that the main variables in the life processes at the molecular level are the conforma- tion of biological macromolecules and their frontier electrons a formalism of quantum theory on conformation-electron sys...Assuming that the main variables in the life processes at the molecular level are the conforma- tion of biological macromolecules and their frontier electrons a formalism of quantum theory on conformation-electron system is proposed. Based on the quantum theory of conformation-electron system, the protein folding is regarded as a quantum transition between torsion states on polypep- tide chain, and the folding rate is calculated by nonadiabatic operator method. The rate calculation is generalized to the case of frequency variation in folding. An analytical form of protein folding rate formula is obtained, which can be served as a useful tool for further studying protein folding. The application of the rate theory to explain the protein folding experiments is briefly summarized. It includes the inertial moment dependence of folding rate, the unified description of two-state and multistate protein folding, the relationship of folding and unfolding rates versus denaturant concen- tration, the distinction between exergonic and endergonic foldings, the ultrafast and the downhill folding viewed from quantum folding theory, and, finally, the temperature dependence of folding rate and the interpretation of its non-Arrhenius behaviors. All these studies support the view that the protein folding is essentially a quantum transition between conformational states.展开更多
The emergence of exotic quantum phenomena in frustrated magnets is rapidly driving the development of quantum many-body physics,raising fundamental questions on the nature of quantum phase transitions.Here we unveil t...The emergence of exotic quantum phenomena in frustrated magnets is rapidly driving the development of quantum many-body physics,raising fundamental questions on the nature of quantum phase transitions.Here we unveil the behaviour of emergent symmetry involving two extraordinarily representative phenomena,i.e.,the deconfined quantum critical point(DQCP)and the quantum spin liquid(QSL)state.Via large-scale tensor network simulations,we study a spatially anisotropic spin-1/2 square-lattice frustrated antiferromagnetic(AFM)model,namely the J1x-J1y-J2 model,which contains anisotropic nearestneighbor couplings J1x,J1y and the next nearest neighbor coupling J2.For small J1y/J1x,by tuning J2,a direct continuous transition between the AFM and valence bond solid phase is observed.With growing J1y/J1x,a gapless QSL phase gradually emerges between the AFM and VBS phases.We observe an emergent O(4)symmetry along the AFM–VBS transition line,which is consistent with the prediction of DQCP theory.Most surprisingly,we find that such an emergent O(4)symmetry holds for the whole QSL–VBS transition line as well.These findings reveal the intrinsic relationship between the QSL and DQCP from categorical symmetry point of view,and strongly constrain the quantum field theory description of the QSL phase.The phase diagram and critical exponents presented in this paper are of direct relevance to future experiments on frustrated magnets and cold atom systems.展开更多
We investigate the effectiveness of entropic uncertainty, entanglement and steering in discerning quantum phase transitions(QPTs). Specifically, we observe significant fluctuations in entropic uncertainty as the drivi...We investigate the effectiveness of entropic uncertainty, entanglement and steering in discerning quantum phase transitions(QPTs). Specifically, we observe significant fluctuations in entropic uncertainty as the driving parameter traverses the phase transition point. It is observed that the entropic uncertainty, entanglement and quantum steering, based on the electron distribution probability, can serve as indicators for detecting QPTs. Notably, we reveal an intriguing anticorrelation relationship between entropic uncertainty and entanglement in the Aubry–André model. Moreover, we explore the feasibility of detecting a QPT when the period parameter is a rational number. These observations open up new and efficient avenues for probing QPTs.展开更多
Cooperative luminescence(CL)occurs in spectral regions in which single ions do not have energy levels.It was first observed more than 40 years ago,and all results reported so far are from a pair of ions.In this work,u...Cooperative luminescence(CL)occurs in spectral regions in which single ions do not have energy levels.It was first observed more than 40 years ago,and all results reported so far are from a pair of ions.In this work,upconverted CL of three Yb^(3+) ions was observed in the ultraviolet(UV)region under near-infrared(NIR)excitation.The UV CL intensity showed a cubic dependence on the NIR pump power,whereas the luminescence lifetime was nearly one-third the luminescence lifetime of single Yb^(3+) ions.The triplet CL(TCL)has a clear spectral structure,in which most emission peaks are consistent with the self-convoluted spectra from single Yb^(3+) ions.Blue shifts were observed for certain peaks,indicating complex interactions among the excited Yb^(3+) ions.The probability of the TCL process versus the average distances among three Yb^(3+) ions was derived via the first-and second-order corrections to the wave functions of lanthanide ions,indicating that the formation of Yb^(3+) clusters containing closely spaced ions favors the occurrence of the multi-ion interaction processes.Furthermore,the cooperative sensitization of one Gd^(3+) ion by four excited Yb^(3+) ions(Yb^(3+)-tetramer)was demonstrated experimentally,which exhibited a novel upconversion mechanism—cluster sensitization.Our results are intriguing for further exploring quantum transitions that simultaneously involve multiple ions.展开更多
Magnetic impurities in superconductors are of increasing interest due to emergent Yu-Shiba-Rusinov(YSR)states and Majorana zero modes for fault-tolerant quantum computation.However,a direct relationship between the YS...Magnetic impurities in superconductors are of increasing interest due to emergent Yu-Shiba-Rusinov(YSR)states and Majorana zero modes for fault-tolerant quantum computation.However,a direct relationship between the YSR multiple states and magnetic anisotropy splitting of quantum impurity spins remains poorly characterized.By using scanning tunneling microscopy,we systematically resolve individual transition-metal(Fe,Cr,and Ni)impurities induced YSR multiplets as well as their Zeeman effects in the K_(3)C_(60)superconductor.The YSR multiplets show identical d orbital-like wave functions that are symmetry-mismatched to the threefold K_(3)C_(60)(111)host surface,breaking point-group symmetries of the spatial distribution of YSR bound states in real space.Remarkably,we identify an unprecedented fermion-parity-preserving quantum phase transition between ground states with opposite signs of the uniaxial magnetic anisotropy that can be manipulated by an external magnetic field.These findings can be readily understood in terms of anisotropy splitting of quantum impurity spins,and thus elucidate the intricate interplay between the magnetic anisotropy and YSR multiplets.展开更多
We study the relationship between quench dynamics of entanglement and quantum phase transition in the antiferromagnetic Ising model with the Dzyaloshinskii–Moriya(DM)interaction by using the quantum renormalization-g...We study the relationship between quench dynamics of entanglement and quantum phase transition in the antiferromagnetic Ising model with the Dzyaloshinskii–Moriya(DM)interaction by using the quantum renormalization-group method and the definition of negativity.Two types of quench protocols(i)adding the DM interaction suddenly and(ii)rotating the spins around x axis are considered to drive the dynamics of the system,respectively.By comparing the behaviors of entanglement in both types of quench protocols,the effects of quench on dynamics of entanglement are studied.It is found that there is the same characteristic time at which the negativity firstly reaches its maximum although the system shows different dynamical behaviors.Especially,the characteristic time can accurately reflect the quantum phase transition from antiferromagnetic to saturated chiral phases in the system.In addition,the correlation length exponent can be obtained by exploring the nonanalytic and scaling behaviors of the derivative of the characteristic time.展开更多
Quantum anomalous Hall(QAH) insulators have excellent properties driven by fancy topological physics, but their practical application is greatly hindered by the observed temperature of liquid nitrogen, and the QAH ins...Quantum anomalous Hall(QAH) insulators have excellent properties driven by fancy topological physics, but their practical application is greatly hindered by the observed temperature of liquid nitrogen, and the QAH insulator with high Chern number is conducive to spintronic devices with lower energy consumption. Here, we find that monolayer Fe SIn is a good candidate for realizing the QAH phase;it exhibits a high magnetic transition temperature of 221 K and tunable C = ±2 with respect to magnetization orientation in the y–z plane. After the application of biaxial strain, the magnetic axis shifts from the x–y plane to the z direction, and the effect of the high C and ferromagnetic ground state on the stress is robust. Also, the effect of correlation U on C has been examined. These properties are rooted in the large size of the Fe atom that contributes to ferromagnetic kinetic exchange with neighboring Fe atoms. These findings demonstrate monolayer Fe SIn to be a major template for probing novel QAH devices at higher temperatures.展开更多
The REAgSb_(2)(RE = rare earth and Y) family has drawn considerable research interest because the two-dimensional Sb net in their crystal structures hosts topological fermions and hence rich topological properties. We...The REAgSb_(2)(RE = rare earth and Y) family has drawn considerable research interest because the two-dimensional Sb net in their crystal structures hosts topological fermions and hence rich topological properties. We report herein the magnetization and magnetotransport measurements of SmAgSb_(2) single crystal, which unveil very large magnetoresistance and high carrier mobility up to 6.2 × 10^(3)% and 5.58 × 10^(3)cm^(2)·V^(-1)·s^(-1), respectively. The analysis of both Shubnikov–de Haas and de Haas–van Alphen quantum oscillations indicates nontrivial Berry phases in the paramagnetic state while trivial Berry curvature in the antiferromagnetic state, indicating a topological phase transition induced by the antiferromagnetic order. It is also supported by the first-principles calculations. The results not only provide a new interesting topological material but also offer valuable insights into the correlation between magnetism and nontrivial topological states.展开更多
Based on the rapid experimental developments of circuit QED,we propose a feasible scheme to simulate the spin-boson model with superconducting circuits,which can be used to detect quantum Kosterlitz-Thouless(KT) phase...Based on the rapid experimental developments of circuit QED,we propose a feasible scheme to simulate the spin-boson model with superconducting circuits,which can be used to detect quantum Kosterlitz-Thouless(KT) phase transition.We design the spinboson model by using a superconducting phase qubit coupled to a semi-infinite transmission line,which is regarded as a bosonic reservoir with a continuum spectrum.By tuning the bias current or the coupling capacitance,the quantum KT transition can be directly detected through tomography measurement on the states of the phase qubit.We also estimate the experimental parameters using the numerical renormalization group method.展开更多
Spontaneous symmetry breaking(SSB)plays a central role in understanding a large variety of phenomena associated with phase transitions,such as superfluid and superconductivity.So far,the transition from a symmetric va...Spontaneous symmetry breaking(SSB)plays a central role in understanding a large variety of phenomena associated with phase transitions,such as superfluid and superconductivity.So far,the transition from a symmetric vacuum to a macroscopically ordered phase has been substantially explored.The process bridging these two distinct phases is critical to understanding how a classical world emerges from a quantum phase transition,but so far remains unexplored in experiment.We here report an experimental demonstration of such a process with a quantum Rabi model engineered with a superconducting circuit.We move the system from the normal phase to the superradiant phase featuring two symmetry-breaking field components,one of which is observed to emerge as the classical reality.The results demonstrate that the environment-induced decoherence plays a critical role in the SSB.展开更多
Biomass-H_(2)O gasification is a complex thermochemical reaction,including three processes of volatile removal:homogeneous/heterogeneous reforming,biochar gasification and etching.The rate-determining step is biochar-...Biomass-H_(2)O gasification is a complex thermochemical reaction,including three processes of volatile removal:homogeneous/heterogeneous reforming,biochar gasification and etching.The rate-determining step is biochar-H_(2)O gasification and etching so the DFT is carried out to see the catalytic role of different metal elements(K/Ni)in the zigzag biochar model.The calculation results show that the gasification of biochar-H_(2)O needs to go through four processes:dissociative adsorption of water,hydrogen transfer(hydrogen desorption,hydrogen atom transfer),carbon dissolution and CO desorption.The energy barrier indicated that the most significant step in reducing the activation energy of K is reflected in the hydrogen transfer step,which is reduced from 374.14 kJ/mol to 152.41 kJ/mol;the catalytic effect of Ni is mainly reflected in the carbon dissolution step,which is reduced from 122.34 kJ/mol to 84.8 kJ/mol.The existence of K causes the edge to have a stronger attraction to H and does not destroy theπbonds of biochar molecules.The destruction ofπbonds is mainly due to the role of H free radicals,while the destruction ofπbonds will lead to easier C-C bond rupture.Ni shows a strong attraction to O in OH,which forms strong Ni-O chemical bonds.Ni can also destroy the aromatic structure directly,making the gasification easier to happen.This study explored the catalytic mechanism of K/Ni on the biochar-H_(2)O gasification at the molecular level and looked forward to the potential synergy of K/Ni,laying a foundation for experimental research and catalyst design.展开更多
Herein,we propose an experimentally feasible scheme to show the quantum phase transition of the Jaynes-Cummings(JC)model by modulating the transition frequency of a two-level system in a quantum Rabi model with strong...Herein,we propose an experimentally feasible scheme to show the quantum phase transition of the Jaynes-Cummings(JC)model by modulating the transition frequency of a two-level system in a quantum Rabi model with strong coupling.By tuning the modulation frequency and amplitude,the ratio of the effective coupling strength of the rotating terms to the effective cavity(atomic transition)frequency can enter the deep-strong coupling regime,while the counter-rotating terms can be neglected.Thus,a deep-strong JC model is obtained.The ratio of the coupling strength to resonance frequencies in the deep-strong JC model is two orders of magnitude larger than the corresponding ratio in the original quantum Rabi model.Our scheme can be employed in atom-cavity resonance and off-resonance cases,and it is valid over a broad range.The nonzero average cavity photons of the ground state indicate the emergence of a quantum phase transition.Further,we demonstrate the dependence of the phase diagram on the atom-cavity detuning and modulation parameters.All the parameters used in our scheme are within the reach of current experimental technology.Our scheme provides a new mechanism for investigating the critical phenomena of finite-sized systems without requiring classical field limits,thereby opening a door for studying fundamental quantum phenomena occurring in the ultrastrong and even deep-strong coupling regimes.展开更多
基金the National Natural Science Foundation of China (Grant No. 10774063)
文摘The transition energies, wavelengths and dipole oscillator strengths of 1s22p-1s2nd (3≤n≤9) for Mn22+ ion are calculated. The fine structure splittings of 1s2nd (n≤9) states for this ion are also evaluated. In calculating energy, the higher-order relativistic contribution is estimated under a hydrogenic approximation. The quantum defect of Rydberg series 1s2nd is determined according to the quantum defect theory. The results obtained in this paper excellently agree with the experi-mental data available in literatures.
基金supported by the National Natural Science Foundation of China (Grant No 10774063)
文摘The transition energies, wavelengths and dipole oscillator strengths of 1s^22p-1s^2nd （3 ≤ n ≤ 9） for Cr^21＋ ion are calculated. The fine structure splittings of 1s^2nd （n ≤ 9） states for this ion are also calculated. In calculating energy, we have estimated the higher-order relativistic contribution under a hydrogenic approximation. The quantum defect of Rydberg series 1s^2nd is determined according to the quantum defect theory. The results obtained in this paper excellently agree with the experimental data available in the literature. Combining the quantum defect theory with the discrete oscillator strengths, the discrete oscillator strengths for the transitions from initial state 1s^22p to highly excited 1s^2nd states （n ≥ 10） and the oscillator strength density corresponding to the bound-free transitions are obtained.
文摘Assuming that the main variables in the life processes at the molecular level are the conforma- tion of biological macromolecules and their frontier electrons a formalism of quantum theory on conformation-electron system is proposed. Based on the quantum theory of conformation-electron system, the protein folding is regarded as a quantum transition between torsion states on polypep- tide chain, and the folding rate is calculated by nonadiabatic operator method. The rate calculation is generalized to the case of frequency variation in folding. An analytical form of protein folding rate formula is obtained, which can be served as a useful tool for further studying protein folding. The application of the rate theory to explain the protein folding experiments is briefly summarized. It includes the inertial moment dependence of folding rate, the unified description of two-state and multistate protein folding, the relationship of folding and unfolding rates versus denaturant concen- tration, the distinction between exergonic and endergonic foldings, the ultrafast and the downhill folding viewed from quantum folding theory, and, finally, the temperature dependence of folding rate and the interpretation of its non-Arrhenius behaviors. All these studies support the view that the protein folding is essentially a quantum transition between conformational states.
基金supported by the National Key R&D Program of China(2022YFA1403700)the National Natural Science Foundation of China(NSFC)and the Research Grants Council(RGC)Joint Research Scheme of the Hong Kong Research Grants Council(N-CUHK427/18)+4 种基金the National Natural Science Foundation of China(12141402)supported by the Science,Technology and Innovation Commission of Shenzhen Municipality(ZDSYS20190902092905285)Guangdong Basic and Applied Basic Research Foundation(2020B1515120100)Center for Computational Science and Engineering at Southern University of Science and Technology.S.S.G.was supported by the National Natural Science Foundation of China(11874078 and 11834014)the Dongguan Key Laboratory of Artificial Intelligence Design for Advanced Materials.
文摘The emergence of exotic quantum phenomena in frustrated magnets is rapidly driving the development of quantum many-body physics,raising fundamental questions on the nature of quantum phase transitions.Here we unveil the behaviour of emergent symmetry involving two extraordinarily representative phenomena,i.e.,the deconfined quantum critical point(DQCP)and the quantum spin liquid(QSL)state.Via large-scale tensor network simulations,we study a spatially anisotropic spin-1/2 square-lattice frustrated antiferromagnetic(AFM)model,namely the J1x-J1y-J2 model,which contains anisotropic nearestneighbor couplings J1x,J1y and the next nearest neighbor coupling J2.For small J1y/J1x,by tuning J2,a direct continuous transition between the AFM and valence bond solid phase is observed.With growing J1y/J1x,a gapless QSL phase gradually emerges between the AFM and VBS phases.We observe an emergent O(4)symmetry along the AFM–VBS transition line,which is consistent with the prediction of DQCP theory.Most surprisingly,we find that such an emergent O(4)symmetry holds for the whole QSL–VBS transition line as well.These findings reveal the intrinsic relationship between the QSL and DQCP from categorical symmetry point of view,and strongly constrain the quantum field theory description of the QSL phase.The phase diagram and critical exponents presented in this paper are of direct relevance to future experiments on frustrated magnets and cold atom systems.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12075001 and 12175001)Anhui Provincial Key Research and Development Plan(Grant No.2022b13020004)the Fund of CAS Key Laboratory of Quantum Information(Grant No.KQI201701)。
文摘We investigate the effectiveness of entropic uncertainty, entanglement and steering in discerning quantum phase transitions(QPTs). Specifically, we observe significant fluctuations in entropic uncertainty as the driving parameter traverses the phase transition point. It is observed that the entropic uncertainty, entanglement and quantum steering, based on the electron distribution probability, can serve as indicators for detecting QPTs. Notably, we reveal an intriguing anticorrelation relationship between entropic uncertainty and entanglement in the Aubry–André model. Moreover, we explore the feasibility of detecting a QPT when the period parameter is a rational number. These observations open up new and efficient avenues for probing QPTs.
基金This work was supported by the National Natural Science Foundation of China(Grants 61178073,11274139,61222508 and 61275189).
文摘Cooperative luminescence(CL)occurs in spectral regions in which single ions do not have energy levels.It was first observed more than 40 years ago,and all results reported so far are from a pair of ions.In this work,upconverted CL of three Yb^(3+) ions was observed in the ultraviolet(UV)region under near-infrared(NIR)excitation.The UV CL intensity showed a cubic dependence on the NIR pump power,whereas the luminescence lifetime was nearly one-third the luminescence lifetime of single Yb^(3+) ions.The triplet CL(TCL)has a clear spectral structure,in which most emission peaks are consistent with the self-convoluted spectra from single Yb^(3+) ions.Blue shifts were observed for certain peaks,indicating complex interactions among the excited Yb^(3+) ions.The probability of the TCL process versus the average distances among three Yb^(3+) ions was derived via the first-and second-order corrections to the wave functions of lanthanide ions,indicating that the formation of Yb^(3+) clusters containing closely spaced ions favors the occurrence of the multi-ion interaction processes.Furthermore,the cooperative sensitization of one Gd^(3+) ion by four excited Yb^(3+) ions(Yb^(3+)-tetramer)was demonstrated experimentally,which exhibited a novel upconversion mechanism—cluster sensitization.Our results are intriguing for further exploring quantum transitions that simultaneously involve multiple ions.
基金financially supported by the National Key Research and Development Program of China(2022YFA1403100,2017YFA0304600)the National Natural Science Foundation of China(12141403,52388201)+1 种基金the Suzhou Science and Technology Program(SJC2021009)Nano-X from the Suzhou Institute of Nano-Tech and Nano-Bionics(SINANO),the Chinese Academy of Sciences.
文摘Magnetic impurities in superconductors are of increasing interest due to emergent Yu-Shiba-Rusinov(YSR)states and Majorana zero modes for fault-tolerant quantum computation.However,a direct relationship between the YSR multiple states and magnetic anisotropy splitting of quantum impurity spins remains poorly characterized.By using scanning tunneling microscopy,we systematically resolve individual transition-metal(Fe,Cr,and Ni)impurities induced YSR multiplets as well as their Zeeman effects in the K_(3)C_(60)superconductor.The YSR multiplets show identical d orbital-like wave functions that are symmetry-mismatched to the threefold K_(3)C_(60)(111)host surface,breaking point-group symmetries of the spatial distribution of YSR bound states in real space.Remarkably,we identify an unprecedented fermion-parity-preserving quantum phase transition between ground states with opposite signs of the uniaxial magnetic anisotropy that can be manipulated by an external magnetic field.These findings can be readily understood in terms of anisotropy splitting of quantum impurity spins,and thus elucidate the intricate interplay between the magnetic anisotropy and YSR multiplets.
基金Project supported by the National Natural Science Foundation of China(Grant No.11675090)the Natural Science Foundation of Shandong Provincie,China(Grant No.ZR2022MA041)。
文摘We study the relationship between quench dynamics of entanglement and quantum phase transition in the antiferromagnetic Ising model with the Dzyaloshinskii–Moriya(DM)interaction by using the quantum renormalization-group method and the definition of negativity.Two types of quench protocols(i)adding the DM interaction suddenly and(ii)rotating the spins around x axis are considered to drive the dynamics of the system,respectively.By comparing the behaviors of entanglement in both types of quench protocols,the effects of quench on dynamics of entanglement are studied.It is found that there is the same characteristic time at which the negativity firstly reaches its maximum although the system shows different dynamical behaviors.Especially,the characteristic time can accurately reflect the quantum phase transition from antiferromagnetic to saturated chiral phases in the system.In addition,the correlation length exponent can be obtained by exploring the nonanalytic and scaling behaviors of the derivative of the characteristic time.
基金Project supported by the National Natural Science Foundation of China (Grant No. 52173283)the Taishan Scholar Program of Shandong Province,China (Grant No. ts20190939)the Independent Cultivation Program of Innovation Team of Jinan City (Grant No. 2021GXRC043)。
文摘Quantum anomalous Hall(QAH) insulators have excellent properties driven by fancy topological physics, but their practical application is greatly hindered by the observed temperature of liquid nitrogen, and the QAH insulator with high Chern number is conducive to spintronic devices with lower energy consumption. Here, we find that monolayer Fe SIn is a good candidate for realizing the QAH phase;it exhibits a high magnetic transition temperature of 221 K and tunable C = ±2 with respect to magnetization orientation in the y–z plane. After the application of biaxial strain, the magnetic axis shifts from the x–y plane to the z direction, and the effect of the high C and ferromagnetic ground state on the stress is robust. Also, the effect of correlation U on C has been examined. These properties are rooted in the large size of the Fe atom that contributes to ferromagnetic kinetic exchange with neighboring Fe atoms. These findings demonstrate monolayer Fe SIn to be a major template for probing novel QAH devices at higher temperatures.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12004405,12334008,and 12374148)the Double First-Class Initiative Fund of Shanghai Tech University+2 种基金the Analytical Instrumentation Center of Shanghai Tech University(Grant No.SPST-AIC10112914)the research fund from the Shanghai Sailing Program(Grant No.23YF1426900)the fund from the National Key R&D Program of China(Grant Nos.2022YFA1402702 and 2021YFA1401600)。
文摘The REAgSb_(2)(RE = rare earth and Y) family has drawn considerable research interest because the two-dimensional Sb net in their crystal structures hosts topological fermions and hence rich topological properties. We report herein the magnetization and magnetotransport measurements of SmAgSb_(2) single crystal, which unveil very large magnetoresistance and high carrier mobility up to 6.2 × 10^(3)% and 5.58 × 10^(3)cm^(2)·V^(-1)·s^(-1), respectively. The analysis of both Shubnikov–de Haas and de Haas–van Alphen quantum oscillations indicates nontrivial Berry phases in the paramagnetic state while trivial Berry curvature in the antiferromagnetic state, indicating a topological phase transition induced by the antiferromagnetic order. It is also supported by the first-principles calculations. The results not only provide a new interesting topological material but also offer valuable insights into the correlation between magnetism and nontrivial topological states.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11004065,11104057 and 11125417)the Natural Science Foundation of Guangdong Province (Grant No.10451063101006312)+1 种基金the State Key Program for Basic Research of China(Grant No. 2011CB922104)the GRF and CRF of the RGC of Hong Kong
文摘Based on the rapid experimental developments of circuit QED,we propose a feasible scheme to simulate the spin-boson model with superconducting circuits,which can be used to detect quantum Kosterlitz-Thouless(KT) phase transition.We design the spinboson model by using a superconducting phase qubit coupled to a semi-infinite transmission line,which is regarded as a bosonic reservoir with a continuum spectrum.By tuning the bias current or the coupling capacitance,the quantum KT transition can be directly detected through tomography measurement on the states of the phase qubit.We also estimate the experimental parameters using the numerical renormalization group method.
基金supported by the National Natural Science Foundation of China(Grant Nos.11874114,12274080,and 11875108)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0300200)。
文摘Spontaneous symmetry breaking(SSB)plays a central role in understanding a large variety of phenomena associated with phase transitions,such as superfluid and superconductivity.So far,the transition from a symmetric vacuum to a macroscopically ordered phase has been substantially explored.The process bridging these two distinct phases is critical to understanding how a classical world emerges from a quantum phase transition,but so far remains unexplored in experiment.We here report an experimental demonstration of such a process with a quantum Rabi model engineered with a superconducting circuit.We move the system from the normal phase to the superradiant phase featuring two symmetry-breaking field components,one of which is observed to emerge as the classical reality.The results demonstrate that the environment-induced decoherence plays a critical role in the SSB.
基金Sponsored by the National Natural Science Foundation of China(Grant No.52276180)the Natural Science Foundation of Heilongjiang Province(Grant No.YQ2022E026).
文摘Biomass-H_(2)O gasification is a complex thermochemical reaction,including three processes of volatile removal:homogeneous/heterogeneous reforming,biochar gasification and etching.The rate-determining step is biochar-H_(2)O gasification and etching so the DFT is carried out to see the catalytic role of different metal elements(K/Ni)in the zigzag biochar model.The calculation results show that the gasification of biochar-H_(2)O needs to go through four processes:dissociative adsorption of water,hydrogen transfer(hydrogen desorption,hydrogen atom transfer),carbon dissolution and CO desorption.The energy barrier indicated that the most significant step in reducing the activation energy of K is reflected in the hydrogen transfer step,which is reduced from 374.14 kJ/mol to 152.41 kJ/mol;the catalytic effect of Ni is mainly reflected in the carbon dissolution step,which is reduced from 122.34 kJ/mol to 84.8 kJ/mol.The existence of K causes the edge to have a stronger attraction to H and does not destroy theπbonds of biochar molecules.The destruction ofπbonds is mainly due to the role of H free radicals,while the destruction ofπbonds will lead to easier C-C bond rupture.Ni shows a strong attraction to O in OH,which forms strong Ni-O chemical bonds.Ni can also destroy the aromatic structure directly,making the gasification easier to happen.This study explored the catalytic mechanism of K/Ni on the biochar-H_(2)O gasification at the molecular level and looked forward to the potential synergy of K/Ni,laying a foundation for experimental research and catalyst design.
基金supported by the National Natural Science Foundation of China(Grant No.12075083)。
文摘Herein,we propose an experimentally feasible scheme to show the quantum phase transition of the Jaynes-Cummings(JC)model by modulating the transition frequency of a two-level system in a quantum Rabi model with strong coupling.By tuning the modulation frequency and amplitude,the ratio of the effective coupling strength of the rotating terms to the effective cavity(atomic transition)frequency can enter the deep-strong coupling regime,while the counter-rotating terms can be neglected.Thus,a deep-strong JC model is obtained.The ratio of the coupling strength to resonance frequencies in the deep-strong JC model is two orders of magnitude larger than the corresponding ratio in the original quantum Rabi model.Our scheme can be employed in atom-cavity resonance and off-resonance cases,and it is valid over a broad range.The nonzero average cavity photons of the ground state indicate the emergence of a quantum phase transition.Further,we demonstrate the dependence of the phase diagram on the atom-cavity detuning and modulation parameters.All the parameters used in our scheme are within the reach of current experimental technology.Our scheme provides a new mechanism for investigating the critical phenomena of finite-sized systems without requiring classical field limits,thereby opening a door for studying fundamental quantum phenomena occurring in the ultrastrong and even deep-strong coupling regimes.
