Electron-phonon interactions and electron-electron correlations represent two crucial facets of condensed matter physics.For instance,in a half-filled spin-1/2 anti-ferromagnetic chain,the lattice dimerization induced...Electron-phonon interactions and electron-electron correlations represent two crucial facets of condensed matter physics.For instance,in a half-filled spin-1/2 anti-ferromagnetic chain,the lattice dimerization induced by electron-nucleus interaction can be intensified by onsite Coulomb repulsion,resulting in a spin-Peierls state.Through first-principles calculations and crystal structure prediction methods,we have identified that under mild pressures,potassium and ammonia can form stable compounds:R3m K(NH_(3))_(2),Pm3 m K(NH_(3))_(2),and Cm K_(2)(NH_(3))_(3).Our predictions suggest that the R3 m K(NH_(3))_(2)exhibits electride characteristics,marked by the formation of interstitial anionic electrons(IAEs)in the interlayer space.These IAEs are arranged in quasi-two-dimensional triangular arrays.With increasing pressure,the electronic van-Hove singularity shifts toward the Fermi level,resulting in an augmented density of states and the onset of both Peierls and magnetic instabilities.Analyzing these instabilities,we determine that the ground state of the R3 m K(NH_(3))_(2)is the dimerized P2_(1)/m phase with zigzag-type anti-ferromagnetic IAEs.This state can be described by the triangular-lattice antiferromagnetic Heisenberg model with modulated magnetic interactions.Furthermore,we unveil the coexistence and positive interplay between magnetic and Peierls instability,constituting a scenario of spin-Peierls instability unprecedented in realistic 2D materials,particularly involving IAEs.This work provides valuable insights into the coupling of IAEs with the adjacent lattice and their spin correlations in quantum materials.展开更多
The Peierls structural transition in quasi-one-dimensional organic crystals of TTF-TCNQ is investigated in the frame of a more complete physical model. The two most important electron-phonon interaction mechanisms are...The Peierls structural transition in quasi-one-dimensional organic crystals of TTF-TCNQ is investigated in the frame of a more complete physical model. The two most important electron-phonon interaction mechanisms are taken into account simultaneously. One is similar of that of deformation potential and the other is of polaron type. For simplicity, the 2D crystal model is considered. The renormalized phonon spectrum and the phonon polarization operator are calculated in the random phase approximation for different temperatures. The effects of interchain interaction on renormalized acoustic phonons and on the Peierls critical temperature are analyzed.展开更多
We investigate the metal-insulator transition in quasi-one-dimensional organic crystals of tetrathiotetracene-iodide, TTT2I3, in the 2D model. A crystal physical model is applied which takes into account two the most ...We investigate the metal-insulator transition in quasi-one-dimensional organic crystals of tetrathiotetracene-iodide, TTT2I3, in the 2D model. A crystal physical model is applied which takes into account two the most important hole-phonon interaction mechanisms. One is similar to that of deformation potential and the other is of polaron type. The scattering on defects is also considered and it is crucial for the explanation of the transition. The phonon polarization operator and the renormalized phonon spectrum are calculated in the random phase approximation for different temperatures applying the method of Green functions. We show that the transition is of Peierls type. The effect of lattice distortion on the dispersion of renormalized acoustic phonons is analyzed.展开更多
We show that,assisted by the Peierls transition of lattice,as a quasi-one dimensional(Q1D) tight binding system,a M¨obius molecular device can behave as a simple topological insulator.With the Peierls phase trans...We show that,assisted by the Peierls transition of lattice,as a quasi-one dimensional(Q1D) tight binding system,a M¨obius molecular device can behave as a simple topological insulator.With the Peierls phase transition to form a domain wall,the solitonary zero modes exist as the ground state of this electron-phonon hybrid system,which is protected by the Z_2 topology of the M¨obius strip.The robustness of the ground state prevents these degenerate zero modes from their energy spectrum splitting caused by any perturbation.展开更多
A charge density wave(CDW)ground state is observed in polycrystalline Cu_(2)Se below 125 K,which corresponds to an energy gap of 40.9 meV and an electron-phonon coupling constant of 0.6.Due to the polycrystalline stru...A charge density wave(CDW)ground state is observed in polycrystalline Cu_(2)Se below 125 K,which corresponds to an energy gap of 40.9 meV and an electron-phonon coupling constant of 0.6.Due to the polycrystalline structure,the Peierls transition process has been expanded to a wide temperature range from 90 K to 160 K.The Hall carrier concentration shows a continuous decrease from 2.1×10^(20)to 1.6×10^(20)cm^(-3)in the temperature range from 160 K to 90 K,while almost unchanged above 160 K and below 90 K.After entering the CDW ground state,a wave-like fluctuation was observed in theI-Vcurve near 50 K,which exhibits a periodic negative differential resistivity in an applied electric field due to the current.We also investigated the doping effect of Zn,Ni,and Te on the CDWground state.Both Zn and Ni doped Cu_(2)Se show a CDW character with increased energy gap and electron-phonon coupling constant,but no notable Peierls transition was observed in Te doped Cu_(2)Se.Similar wave-likeI-Vcurve was also seen in Cu_(1.98)Zn_(0.02)Se near 40 K.The regular fluctuation in the dcI-Vcurve was not magnetic field sensitive,but temperature and sample size sensitive.展开更多
The Peierls structural transition in the TTT<sub>2</sub>I<sub>3</sub> (tetrathiotetracene-iodide) crystal, for different values of carrier concentration is studied in 3D approximation. A crysta...The Peierls structural transition in the TTT<sub>2</sub>I<sub>3</sub> (tetrathiotetracene-iodide) crystal, for different values of carrier concentration is studied in 3D approximation. A crystal physical model is applied that considers two of the most important hole-phonon interactions. The first interaction describes the deformation potential and the second one is of polaron type. In the presented physical model, the interaction of carriers with the structural defects is taken into account. This is crucial for the explanation of the transition. The renormalized phonon spectrum is calculated in the random phase approximation for different temperatures applying the method of Green functions. The renormalized phonon frequencies for different temperatures are presented in two cases. In the first case the interaction between TTT chains is neglected. In the second one, this interaction is taken into account. Computer simulations for the 3D physical model of the TTT<sub>2</sub>I<sub>3</sub> crystal are performed for different values of dimensionless Fermi momentum <em>k</em><sub>F</sub>, that is determined by variation of carrier concentration. It is shown that the transition is of Peierls type and strongly depends on iodine concentration. Finally, the Peierls critical temperature was determined.展开更多
基金financial support from the National Key R&D Program of China(2022YFA1403201)the National Natural Science Foundation of China(12125404,11974162,and 11834006)the Fundamental Research Funds for the Central Universities。
文摘Electron-phonon interactions and electron-electron correlations represent two crucial facets of condensed matter physics.For instance,in a half-filled spin-1/2 anti-ferromagnetic chain,the lattice dimerization induced by electron-nucleus interaction can be intensified by onsite Coulomb repulsion,resulting in a spin-Peierls state.Through first-principles calculations and crystal structure prediction methods,we have identified that under mild pressures,potassium and ammonia can form stable compounds:R3m K(NH_(3))_(2),Pm3 m K(NH_(3))_(2),and Cm K_(2)(NH_(3))_(3).Our predictions suggest that the R3 m K(NH_(3))_(2)exhibits electride characteristics,marked by the formation of interstitial anionic electrons(IAEs)in the interlayer space.These IAEs are arranged in quasi-two-dimensional triangular arrays.With increasing pressure,the electronic van-Hove singularity shifts toward the Fermi level,resulting in an augmented density of states and the onset of both Peierls and magnetic instabilities.Analyzing these instabilities,we determine that the ground state of the R3 m K(NH_(3))_(2)is the dimerized P2_(1)/m phase with zigzag-type anti-ferromagnetic IAEs.This state can be described by the triangular-lattice antiferromagnetic Heisenberg model with modulated magnetic interactions.Furthermore,we unveil the coexistence and positive interplay between magnetic and Peierls instability,constituting a scenario of spin-Peierls instability unprecedented in realistic 2D materials,particularly involving IAEs.This work provides valuable insights into the coupling of IAEs with the adjacent lattice and their spin correlations in quantum materials.
文摘The Peierls structural transition in quasi-one-dimensional organic crystals of TTF-TCNQ is investigated in the frame of a more complete physical model. The two most important electron-phonon interaction mechanisms are taken into account simultaneously. One is similar of that of deformation potential and the other is of polaron type. For simplicity, the 2D crystal model is considered. The renormalized phonon spectrum and the phonon polarization operator are calculated in the random phase approximation for different temperatures. The effects of interchain interaction on renormalized acoustic phonons and on the Peierls critical temperature are analyzed.
文摘We investigate the metal-insulator transition in quasi-one-dimensional organic crystals of tetrathiotetracene-iodide, TTT2I3, in the 2D model. A crystal physical model is applied which takes into account two the most important hole-phonon interaction mechanisms. One is similar to that of deformation potential and the other is of polaron type. The scattering on defects is also considered and it is crucial for the explanation of the transition. The phonon polarization operator and the renormalized phonon spectrum are calculated in the random phase approximation for different temperatures applying the method of Green functions. We show that the transition is of Peierls type. The effect of lattice distortion on the dispersion of renormalized acoustic phonons is analyzed.
基金Supported by the National Natural Science Foundation of China under Grant No.11504241the Natural Science Foundation of Shenzhen University under Grant No.201551
文摘We show that,assisted by the Peierls transition of lattice,as a quasi-one dimensional(Q1D) tight binding system,a M¨obius molecular device can behave as a simple topological insulator.With the Peierls phase transition to form a domain wall,the solitonary zero modes exist as the ground state of this electron-phonon hybrid system,which is protected by the Z_2 topology of the M¨obius strip.The robustness of the ground state prevents these degenerate zero modes from their energy spectrum splitting caused by any perturbation.
基金This work is supported by“Solid State Solar-Thermal Energy Conversion Center(S3TEC)”an Energy Frontier Research Center funded by the U.S.Department of Energy,Office of Science,Office of Basic Energy Science under award number DE-SC0001299/DEFG02-09ER46577(Z.F.R.).C.O.wishes to thank Robert D.Farrell,S.J.for editing the MS and the Trustees of Boston College for their financial support.
文摘A charge density wave(CDW)ground state is observed in polycrystalline Cu_(2)Se below 125 K,which corresponds to an energy gap of 40.9 meV and an electron-phonon coupling constant of 0.6.Due to the polycrystalline structure,the Peierls transition process has been expanded to a wide temperature range from 90 K to 160 K.The Hall carrier concentration shows a continuous decrease from 2.1×10^(20)to 1.6×10^(20)cm^(-3)in the temperature range from 160 K to 90 K,while almost unchanged above 160 K and below 90 K.After entering the CDW ground state,a wave-like fluctuation was observed in theI-Vcurve near 50 K,which exhibits a periodic negative differential resistivity in an applied electric field due to the current.We also investigated the doping effect of Zn,Ni,and Te on the CDWground state.Both Zn and Ni doped Cu_(2)Se show a CDW character with increased energy gap and electron-phonon coupling constant,but no notable Peierls transition was observed in Te doped Cu_(2)Se.Similar wave-likeI-Vcurve was also seen in Cu_(1.98)Zn_(0.02)Se near 40 K.The regular fluctuation in the dcI-Vcurve was not magnetic field sensitive,but temperature and sample size sensitive.
文摘The Peierls structural transition in the TTT<sub>2</sub>I<sub>3</sub> (tetrathiotetracene-iodide) crystal, for different values of carrier concentration is studied in 3D approximation. A crystal physical model is applied that considers two of the most important hole-phonon interactions. The first interaction describes the deformation potential and the second one is of polaron type. In the presented physical model, the interaction of carriers with the structural defects is taken into account. This is crucial for the explanation of the transition. The renormalized phonon spectrum is calculated in the random phase approximation for different temperatures applying the method of Green functions. The renormalized phonon frequencies for different temperatures are presented in two cases. In the first case the interaction between TTT chains is neglected. In the second one, this interaction is taken into account. Computer simulations for the 3D physical model of the TTT<sub>2</sub>I<sub>3</sub> crystal are performed for different values of dimensionless Fermi momentum <em>k</em><sub>F</sub>, that is determined by variation of carrier concentration. It is shown that the transition is of Peierls type and strongly depends on iodine concentration. Finally, the Peierls critical temperature was determined.
