Using mean-field theory, we have studied the effect of quantum transverse anisotropies with RKKY interaction on the multi-layer transition and magnetic properties of the spin-1 Blume-Capel model of a system formed by ...Using mean-field theory, we have studied the effect of quantum transverse anisotropies with RKKY interaction on the multi-layer transition and magnetic properties of the spin-1 Blume-Capel model of a system formed by two magnetic multi-layer materials, of different thicknesses, separated by a non-magnetic spacer of thickness M. It is found that the multilayer magnetic order-disorder transition temperature depends strongly on the value of the transverse anisotropy. The multilayer transition temperature decreases when increasing the transverse anisotropy. Furthermore, there exists a critical quantum transverse anisotropy △xL beyond which the separate transitions occur in the two magnetic layers. The critical transverse anisotropy AxL decreases （increases） on increasing the non-magnetic spacer of thickness M （on increasing the crystal field）, and AxL undergoes oscillations as a function of the Fermi level.展开更多
Understanding the quantum critical phenomena is one of the most important and challenging tasks in condensed matter physics and the two-impurity Anderson model(TIAM) is a good starting point for this exploration. To t...Understanding the quantum critical phenomena is one of the most important and challenging tasks in condensed matter physics and the two-impurity Anderson model(TIAM) is a good starting point for this exploration. To this end,we employ the algebraic equation of motion approach to calculate the TIAM and analytically obtain the explicit singleparticle impurity Green function under the soft cut-off approximation(SCA). This approach effectively incorporates the impurity spacing as an intrinsic parameter. By solving the pole equations of the Green function, we have, for the first time, qualitatively calculated the spectral weight functions of the corresponding low-energy excitations. We find that when the impurity spacing is less than one lattice distance, the dynamic Rudermann–Kittel–Kasuya–Yosida(RKKY) interaction effectively enters, resulting in a rapid increase in the spectral weights of the RKKY phase, which ultimately surpass those of the Kondo phase;while the spectral weights of the Kondo phase are strongly suppressed. From the perspective of spectral weights, we further confirm the existence of a crossover from the Kondo phase to the RKKY phase in the TIAM. Based on these results, the reasons for the phenomenon of the Kondo resonance splitting are also discussed.展开更多
Quantum critical phenomena in the quasi-one-dimensional limit remain an open issue.We report the uniaxial stress effect on the quasi-one-dimensional Kondo lattice CeCo_(2)Ga_(8) by electric transport and AC heat capac...Quantum critical phenomena in the quasi-one-dimensional limit remain an open issue.We report the uniaxial stress effect on the quasi-one-dimensional Kondo lattice CeCo_(2)Ga_(8) by electric transport and AC heat capacity measurements.CeCo_(2)Ga_(8) is speculated to sit in close vicinity but on the quantum-disordered side of a quantum critical point.Upon compressing the c axis,parallel to the Ce-Ce chain,the onset of coherent Kondo effect is enhanced.In contrast,the electronic specific heat diverges more rapidly at low temperature when the intra-chain distance is elongated by compressions along a or b axis.These results suggest that a tensile intra-chain strain(ε_(c)>0)pushes CeCo_(2)Ga_(8) closer to the quantum critical point,while a compressive intra-chain strain(ε_(c)<0)likely causes departure.Our work provides a rare paradigm of manipulation near a quantum critical point in a quasi-1D Kondo lattice by uniaxial stress,and paves the way for further investigations on the unique feature of quantum criticality in the quasi-1D limit.展开更多
We theoretically investigate a device consisting of two quantum dots （QDs） side-coupled to a quantum wire which has many physical ingredients of an artificial heavy fermion system. An extra parameter, the distance L...We theoretically investigate a device consisting of two quantum dots （QDs） side-coupled to a quantum wire which has many physical ingredients of an artificial heavy fermion system. An extra parameter, the distance L between the two QDs, is introduced and it plays an important role on the competition of the Kondo temperature and magnetic coupling. Three different phases are found： antiferromagnetic phase, Kondo phase with spin S = 1/2, and Kondo phase with S = 1, depending on the distance L, the magnetic properties are qualitatively different for different phases： conductance tends to the unitary value 2e2 /h; for the S ： the distance. coupling, and the Kondo temperature. Quantum transport for the S = 1 Kondo and the antiferromagnetic phases, the 1/2 Kondo phase the conductance is strongly dependent onthe distance.展开更多
We have analyzed magnetic order in the one-dimensional Kondo lattice with classical localized spins.To identify relevant low-energy configurations,we combine the exact diagonalization of the electronic system with a d...We have analyzed magnetic order in the one-dimensional Kondo lattice with classical localized spins.To identify relevant low-energy configurations,we combine the exact diagonalization of the electronic system with a dissipative evolution,described by the Landau–Lifshitz-Gilbert equation.We find that spiral states always relax into a more complex form of noncollinear order,characterized by a periodic modulation of the relative angles between neighboring spins.A finite-size scaling analysis shows that the amplitude of the modulation and the gain in free energy remain finite in the thermodynamic limit.Importantly,the wavelength of the modulation is determined by the Fermi wavevector of the unperturbed spiral.This suggests that complex noncollinear order originates from an instability of the unperturbed spirals,which,in the presence of a weak pairing term,may hinder topological superconductivity.Our final phase diagram is obtained by comparing the modulated spiral states with various complex collinear configurations proposed in the literature.展开更多
The topological insulators Bi_(2-x)Fe_(x)Se_(3-x)S_(x) have been investigated by the dc-magnetization,magnetotransport and angle resolved photoemission spectroscopy(ARPES)techniques.With doping of Fe and S,a negative ...The topological insulators Bi_(2-x)Fe_(x)Se_(3-x)S_(x) have been investigated by the dc-magnetization,magnetotransport and angle resolved photoemission spectroscopy(ARPES)techniques.With doping of Fe and S,a negative giant magneto-resistance(MR)is observed for parallel electric and magnetic fields(H||E).The MR behavior at lower magnetic field can be explained with the semi-classical theory whereas the MR behavior at higher field has been attributed to the axial anomaly.Interestingly,the system reached to the quantum limit at low magnetic field(~4.5T).The magnetic ordering can be explained with the presence of both the RKKY(surface)and van-Vleck(bulk)interaction.The ARPES study reveals that a surface gap is suppressed when the magnetic ordering changes from ferromagnetic to anti-ferromagnetic ordering.The ARPES study and the appearance of quantum oscillations(SdH)in the resistivity pattern reveal that the topological surface property is preserved with the co-doping of Fe and S.展开更多
文摘Using mean-field theory, we have studied the effect of quantum transverse anisotropies with RKKY interaction on the multi-layer transition and magnetic properties of the spin-1 Blume-Capel model of a system formed by two magnetic multi-layer materials, of different thicknesses, separated by a non-magnetic spacer of thickness M. It is found that the multilayer magnetic order-disorder transition temperature depends strongly on the value of the transverse anisotropy. The multilayer transition temperature decreases when increasing the transverse anisotropy. Furthermore, there exists a critical quantum transverse anisotropy △xL beyond which the separate transitions occur in the two magnetic layers. The critical transverse anisotropy AxL decreases （increases） on increasing the non-magnetic spacer of thickness M （on increasing the crystal field）, and AxL undergoes oscillations as a function of the Fermi level.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11974420)。
文摘Understanding the quantum critical phenomena is one of the most important and challenging tasks in condensed matter physics and the two-impurity Anderson model(TIAM) is a good starting point for this exploration. To this end,we employ the algebraic equation of motion approach to calculate the TIAM and analytically obtain the explicit singleparticle impurity Green function under the soft cut-off approximation(SCA). This approach effectively incorporates the impurity spacing as an intrinsic parameter. By solving the pole equations of the Green function, we have, for the first time, qualitatively calculated the spectral weight functions of the corresponding low-energy excitations. We find that when the impurity spacing is less than one lattice distance, the dynamic Rudermann–Kittel–Kasuya–Yosida(RKKY) interaction effectively enters, resulting in a rapid increase in the spectral weights of the RKKY phase, which ultimately surpass those of the Kondo phase;while the spectral weights of the Kondo phase are strongly suppressed. From the perspective of spectral weights, we further confirm the existence of a crossover from the Kondo phase to the RKKY phase in the TIAM. Based on these results, the reasons for the phenomenon of the Kondo resonance splitting are also discussed.
文摘Quantum critical phenomena in the quasi-one-dimensional limit remain an open issue.We report the uniaxial stress effect on the quasi-one-dimensional Kondo lattice CeCo_(2)Ga_(8) by electric transport and AC heat capacity measurements.CeCo_(2)Ga_(8) is speculated to sit in close vicinity but on the quantum-disordered side of a quantum critical point.Upon compressing the c axis,parallel to the Ce-Ce chain,the onset of coherent Kondo effect is enhanced.In contrast,the electronic specific heat diverges more rapidly at low temperature when the intra-chain distance is elongated by compressions along a or b axis.These results suggest that a tensile intra-chain strain(ε_(c)>0)pushes CeCo_(2)Ga_(8) closer to the quantum critical point,while a compressive intra-chain strain(ε_(c)<0)likely causes departure.Our work provides a rare paradigm of manipulation near a quantum critical point in a quasi-1D Kondo lattice by uniaxial stress,and paves the way for further investigations on the unique feature of quantum criticality in the quasi-1D limit.
基金supported by National Science Foundation of China under Grant Nos.10974236 and 11074174
文摘We theoretically investigate a device consisting of two quantum dots （QDs） side-coupled to a quantum wire which has many physical ingredients of an artificial heavy fermion system. An extra parameter, the distance L between the two QDs, is introduced and it plays an important role on the competition of the Kondo temperature and magnetic coupling. Three different phases are found： antiferromagnetic phase, Kondo phase with spin S = 1/2, and Kondo phase with S = 1, depending on the distance L, the magnetic properties are qualitatively different for different phases： conductance tends to the unitary value 2e2 /h; for the S ： the distance. coupling, and the Kondo temperature. Quantum transport for the S = 1 Kondo and the antiferromagnetic phases, the 1/2 Kondo phase the conductance is strongly dependent onthe distance.
基金support from the Innovation Program for Quantum Science and Technology under Grant No.2021ZD0301602the National Science Association Funds under Grant No.U2230402+2 种基金supported by FCT-Portugal(PR)the Quant ERA II project‘DQUANT:A Dissipative Quantum Chaos perspective on Near-Term Quantum Computing’via Grant Agreement No.101017733support from FCTPortugal through Grant No.UID/CTM/04540/2020。
文摘We have analyzed magnetic order in the one-dimensional Kondo lattice with classical localized spins.To identify relevant low-energy configurations,we combine the exact diagonalization of the electronic system with a dissipative evolution,described by the Landau–Lifshitz-Gilbert equation.We find that spiral states always relax into a more complex form of noncollinear order,characterized by a periodic modulation of the relative angles between neighboring spins.A finite-size scaling analysis shows that the amplitude of the modulation and the gain in free energy remain finite in the thermodynamic limit.Importantly,the wavelength of the modulation is determined by the Fermi wavevector of the unperturbed spiral.This suggests that complex noncollinear order originates from an instability of the unperturbed spirals,which,in the presence of a weak pairing term,may hinder topological superconductivity.Our final phase diagram is obtained by comparing the modulated spiral states with various complex collinear configurations proposed in the literature.
基金Authors are grateful to CIF,IIT(BHU)for providing magnetic measurement facility.The ARPES measurements were performed with the approval of the Proposal Assessing Committee of the Hiroshima Synchrotron Radiation Center(Proposal Numbers:18AG029 and 18BG031).
文摘The topological insulators Bi_(2-x)Fe_(x)Se_(3-x)S_(x) have been investigated by the dc-magnetization,magnetotransport and angle resolved photoemission spectroscopy(ARPES)techniques.With doping of Fe and S,a negative giant magneto-resistance(MR)is observed for parallel electric and magnetic fields(H||E).The MR behavior at lower magnetic field can be explained with the semi-classical theory whereas the MR behavior at higher field has been attributed to the axial anomaly.Interestingly,the system reached to the quantum limit at low magnetic field(~4.5T).The magnetic ordering can be explained with the presence of both the RKKY(surface)and van-Vleck(bulk)interaction.The ARPES study reveals that a surface gap is suppressed when the magnetic ordering changes from ferromagnetic to anti-ferromagnetic ordering.The ARPES study and the appearance of quantum oscillations(SdH)in the resistivity pattern reveal that the topological surface property is preserved with the co-doping of Fe and S.
