In recent years, mteracting topological insulators have emerged as new frontiers in condensed matter physics, and the hotly studied topological Kondo insulator (TKI) is one of such prototypes. Although its zero-temper...In recent years, mteracting topological insulators have emerged as new frontiers in condensed matter physics, and the hotly studied topological Kondo insulator (TKI) is one of such prototypes. Although its zero-temperature ground-state has been widely investigated, the finite temperature physics on TKI is largely unknown. Here, we explore the finite temperature properties in a simplified model for TKI. namely the one-dimensional p-wave periodic Anderson model, with numerically exact determinant quantum Monte Carlo simulation. It is found that the topological Haldane phase established for groimdstate is still stable against small thermal fluctuation and its characteristic edge magnetization develops at low temperature. Such facts emphasize the robustness of (symmetry-protected) topological order against temperature effect, which always exists at real physical world. Moreover, we use the saturated low-T spin structure factor and the 1/T-law of susceptibility to detect the free edge spin moment, interestingly the low-temperature upturn behaxior of the latter one is similar to experimental finding in SniBg at T < 50 K. It implies that similar physical mechanism may work both for idealized models and realistic correlated electron materials.We have also identified an emergent energy scale Tcr. which signals a crossover into interesting low-T regime and seems to be the expected Ruderman-Kittel- Kasuya Yosida coupling. Finally, the collective Kondo screening effect has been examined and it is heavily reduced at boundary which may give a fruitful playground for novel physics beyond the wellestablished Haldane phase and topological band insulators.展开更多
By using Lanczos exact diagonalization and quantum Monte Carlo combined with stochastic analytic continuation,we study the dynamical properties of the S=1 antiferromagnetic Heisenberg chain with different strengths of...By using Lanczos exact diagonalization and quantum Monte Carlo combined with stochastic analytic continuation,we study the dynamical properties of the S=1 antiferromagnetic Heisenberg chain with different strengths of bond disorder.In the weak disorder region,we find weakly coupled bonds which can induce additional low-energy excitation below the one-magnon mode.As the disorder increases,the average Haldane gap closes at δ_(∆)~0.5 with more and more low-energy excitations coming out.After the critical disorder strength δ_(C)~1,the system reaches a random-singlet phase with prominent sharp peak atω=0 and broad continuum atω>0 of the dynamic spin structure factor.In addition,we analyze the distribution of random spin domains and numerically find three kinds of domains hosting effective spin-1/2 quanta or spin-1 sites in between.These“spins”can form the weakly coupled longrange singlets due to quantum fluctuation which contribute to the sharp peak atω=0.展开更多
By using the transfer matrix method,we discover three types of current,such as the 100%spinvalley polarized current,pure spin-valley current and pure charge current,in a two-terminal graphene system.These types of cur...By using the transfer matrix method,we discover three types of current,such as the 100%spinvalley polarized current,pure spin-valley current and pure charge current,in a two-terminal graphene system.These types of current can be obtained and mutually switched by modulating the parameters of the modified Haldane model(MHM).In our work,these types of current are driven by the thermal bias.Compared with this method of increasing the one-lead temperature(with a fixed temperature difference),the thermal currents can be more effectively strengthened by increasing the temperature difference(with a fixed one-lead temperature).In order to rapidly turn off these currents,we choose to enhance the intensity of the off-resonant circularly polarized light instead of canceling the temperature difference.These results indicate that the graphene system with the MHM has promising applications in the spin and valley caloritronics.展开更多
Absorption spectra of the mixed chain nickelates （（NdxY1-x）2BaNiO5 were measured for different x. Experimentally two evidences for the presence of non-equivalent rare-earth centers （NEREC） were found. First, the ...Absorption spectra of the mixed chain nickelates （（NdxY1-x）2BaNiO5 were measured for different x. Experimentally two evidences for the presence of non-equivalent rare-earth centers （NEREC） were found. First, the linewidths show a very strong broadening for x when the calculated distribution over NEREC is wide. Second, a compficated lineshape of the lowest-frequency line in the region of the 4I9/2→4I1/2 electronic lransition is in good agreement with statistics of NEREC. A simple modeling for the line broadening due to NEREC is suggested.展开更多
基金the National Natural Science Foundation of China under Grant Nos. 11325417, 11674139, and 11704166the Fundamental Research Funds for the Central Universities, Science Challenge Project under Grant No. JCKY2016212A502, SPC-Lab Research Fund (NO. XKFZ201605)the Foundation of LCP.
文摘In recent years, mteracting topological insulators have emerged as new frontiers in condensed matter physics, and the hotly studied topological Kondo insulator (TKI) is one of such prototypes. Although its zero-temperature ground-state has been widely investigated, the finite temperature physics on TKI is largely unknown. Here, we explore the finite temperature properties in a simplified model for TKI. namely the one-dimensional p-wave periodic Anderson model, with numerically exact determinant quantum Monte Carlo simulation. It is found that the topological Haldane phase established for groimdstate is still stable against small thermal fluctuation and its characteristic edge magnetization develops at low temperature. Such facts emphasize the robustness of (symmetry-protected) topological order against temperature effect, which always exists at real physical world. Moreover, we use the saturated low-T spin structure factor and the 1/T-law of susceptibility to detect the free edge spin moment, interestingly the low-temperature upturn behaxior of the latter one is similar to experimental finding in SniBg at T < 50 K. It implies that similar physical mechanism may work both for idealized models and realistic correlated electron materials.We have also identified an emergent energy scale Tcr. which signals a crossover into interesting low-T regime and seems to be the expected Ruderman-Kittel- Kasuya Yosida coupling. Finally, the collective Kondo screening effect has been examined and it is heavily reduced at boundary which may give a fruitful playground for novel physics beyond the wellestablished Haldane phase and topological band insulators.
基金D.X.Y.,J.K.F,and J.H.H are supported by NKRDPC-2017YFA0206203,NKRDPC-2018YFA0306001,NSFC-11974432,GBABRF-2019A1515011337Shenzhen Institute for Quantum Science and Engineering,and Leading Talent Program of Guangdong Special Projects+1 种基金H.Q.W.is supported by NSFC-11804401the Fundamental Research Funds for the Central Universities,Sun Yat-sen University(Grant No.2021qntd27).
文摘By using Lanczos exact diagonalization and quantum Monte Carlo combined with stochastic analytic continuation,we study the dynamical properties of the S=1 antiferromagnetic Heisenberg chain with different strengths of bond disorder.In the weak disorder region,we find weakly coupled bonds which can induce additional low-energy excitation below the one-magnon mode.As the disorder increases,the average Haldane gap closes at δ_(∆)~0.5 with more and more low-energy excitations coming out.After the critical disorder strength δ_(C)~1,the system reaches a random-singlet phase with prominent sharp peak atω=0 and broad continuum atω>0 of the dynamic spin structure factor.In addition,we analyze the distribution of random spin domains and numerically find three kinds of domains hosting effective spin-1/2 quanta or spin-1 sites in between.These“spins”can form the weakly coupled longrange singlets due to quantum fluctuation which contribute to the sharp peak atω=0.
基金supported by the starting foundation of Guangxi University of Science and Technology(Grants No.21Z52)The support from the National Natural Science Foundation of China(No.11847301)the Natural Science Foundation of Chongqing(No.cstc2020jcyj-msxmX0860)are also appreciated。
文摘By using the transfer matrix method,we discover three types of current,such as the 100%spinvalley polarized current,pure spin-valley current and pure charge current,in a two-terminal graphene system.These types of current can be obtained and mutually switched by modulating the parameters of the modified Haldane model(MHM).In our work,these types of current are driven by the thermal bias.Compared with this method of increasing the one-lead temperature(with a fixed temperature difference),the thermal currents can be more effectively strengthened by increasing the temperature difference(with a fixed one-lead temperature).In order to rapidly turn off these currents,we choose to enhance the intensity of the off-resonant circularly polarized light instead of canceling the temperature difference.These results indicate that the graphene system with the MHM has promising applications in the spin and valley caloritronics.
基金supported by the Russian Foundation for Basic Research (08-02-00690-a)the Russian Academy of Sciences under the Prograof Basic Research
文摘Absorption spectra of the mixed chain nickelates （（NdxY1-x）2BaNiO5 were measured for different x. Experimentally two evidences for the presence of non-equivalent rare-earth centers （NEREC） were found. First, the linewidths show a very strong broadening for x when the calculated distribution over NEREC is wide. Second, a compficated lineshape of the lowest-frequency line in the region of the 4I9/2→4I1/2 electronic lransition is in good agreement with statistics of NEREC. A simple modeling for the line broadening due to NEREC is suggested.
