arXiv subjects

Minh-Tien Tran

Publications and source records attributed to Minh-Tien Tran.

At least 19 recordsLinked to original sources

arXiv2026

BCS-BEC crossover of polaritonic condensates in mass-imbalanced semimetal/semiconductor microcavities

The impacts of the mass imbalance and Coulomb interaction on the complex phase structures of the polaritonic condensates and their Bardeen-Cooper-Schrieffer (BCS)--Bose-Einstein condensation (BEC) crossover in semiconductor and semimetal microcavities are investigated. In the framework of the unrestricted Hartree-Fock approximation, a two-band electron-hole model involving photon mode is analyzed by treating Coulomb attraction and light-matter coupling on equal footing. The single-particle spectral functions and the luminescence properties are then examined. In the semiconducting regime, a positive band gap stabilizes tightly bound excitons and yields predominantly BEC-type excitoniclike polaritonic condensates at low density, while increasing excitation density and reducing mass imbalance drives a continuous crossover toward BCS-type pairing with intermediate and photoniclike polaritonic character. In contrast, the semimetallic regime favors itinerant electron-hole pairing, with BCS-type condensates dominating and BEC excitoniclike coherence emerging only at sufficiently strong Coulomb interaction and large mass imbalance situations. The evolution of luminescence spectra provides clear spectroscopic signatures of these crossover phenomena, offering a unified framework for understanding and controlling polaritonic condensates in microcavity systems.

cond-mat.str-el↗

arXiv2025

Solvation enhances folding cooperativity and the topology dependence of folding rates in a lattice protein model

The aqueous solvent profoundly influences protein folding, yet its effects are relatively poorly understood. In this study, we investigate the impact of solvation on the folding of lattice proteins by using Monte Carlo simulations. The proteins are modelled as self-avoiding 27-mer chains on a cubic lattice, with compact native states and structure-based Gō potentials. Each residue that makes no contacts with other residues in a given protein conformation is assigned a solvation energy ε_s , representing its full exposure to the solvent. We find that a negative ε_s , indicating a favorable solvation, increases the cooperativity of the folding transition by lowering the free energy of the unfolded state, increasing the folding free energy barrier, and narrowing the folding routes. This favorable solvation also significantly improves the correlation between folding rates and the native topology, measured by the relative contact order. Our results suggest that Gō model may overestimate the importance of native interactions and a solvation potential countering the native bias can play a significant role. The solvation energy in our model can be related to the polar interaction between water and peptide groups in the protein backbone. It is therefore suggested that the solvation of peptide groups may significantly contribute to the exceptional folding cooperativity and the pronounced topology-dependence of folding rates observed in two-state proteins.

cond-mat.soft↗

arXiv2021

Topological Green function of interacting systems

We construct a Green function, which can identify the topological nature of interacting systems. It is equivalent to the single-particle Green function of effective non-interacting particles, the Bloch Hamiltonian of which is given by the inverse of the full Green function of the original interacting particles at zero frequency. The topological nature of the interacting insulators is originated from the coincidence of the poles and the zeros of the diagonal elements of the constructed Green function. The cross of the zeros in the momentum space closely relates to the topological nature of insulators. As a demonstration, using the zero's cross, we identify the topological phases of magnetic insulators, where both the ionic potential and the spin exchange between conduction electrons and magnetic moments are present together with the spin-orbital coupling. The topological phase identification is consistent with the topological invariant of the magnetic insulators. We also found an antiferromagnetic state with topologically breaking of the spin symmetry, where electrons with one spin orientation are in topological insulating state, while electrons with the opposite spin orientation are in topologically trivial one.

cond-mat.str-el↗

arXiv2020

Magnetic competition in topological kagome magnets

Magnetic competition in topological kagome magnets is studied by incorporating the spin-orbit coupling, the anisotropic Hund coupling and spin exchange into the kagome lattice. Using the Bogoliubov variational principle we find the stable phases at zero and finite temperatures. At zero temperature and in the strong Ising-Hund coupling regime, a magnetic tunability from the out-of-plane ferromagnetism (FM) to the in-plane antiferromagnetism (AFM) is achieved by a universal property of the critical in-plane Hund coupling. At two-thirds filling the phase transition from the out-of-plane FM to the in-plane AFM is accompanied by a topological transition from quantum anomalous Hall (QAH) to quantum anomalous spin Hall (QASH) effect. Nearby half filling a large anomalous Hall conductance is observed at the magnetic phase transition. At finite temperature the out-of-plane FM is stable until a crossing temperature, above which the in-plane AFM is stable, but the out-of-plane FM magnetization is still finite. This suggests a coexistence of these magnetic phases in a finite temperature range.

cond-mat.str-el↗

arXiv2020

Impact of magnetic dopants on magnetic and topological phases in magnetic topological insulators

A topological insulator doped with random magnetic impurities is studied. The system is modelled by the Kane-Mele model with a random spin exchange between conduction electrons and magnetic dopants. The dynamical mean field theory for disordered systems is used to investigate the electron dynamics. The magnetic long-range order and the topological invariant are calculated within the mean field theory. They reveal a rich phase diagram, where different magnetic long-range orders such as antiferromagnetic or ferromagnetic one can exist in the metallic or insulating phases, depending on electron and magnetic impurity fillings. It is found that insulator only occurs at electron half filling, quarter filling and when electron filling is equal to magnetic impurity filling. However, non-trivial topology is observed only in half-filling antiferromagnetic insulator and quarter-filling ferromagnetic insulator. At electron half filling, the spin Hall conductance is quantized and it is robust against magnetic doping, while at electron quarter filling, magnetic dopants drive the ferromagnetic topological insulator to ferromagnetic metal. The quantum anomalous Hall effect is observed only at electron quarter filling and dense magnetic doping.

cond-mat.str-el↗

arXiv2019

Fractionalization of long-range ordered states in a Falicov-Kimball model

A Falicov-Kimball model which thermodynamically reduces the local Coulomb interaction of particles to attraction or repulsion is studied within the dynamical mean-field theory. In the strong interaction regime a fractionalization of particles into charge and spin objects, the physical properties of which are different from the whole particles, is observed in both high- and low-temperature phases. At high temperature and strong interaction the single-particle density of states opens an excitation gap, but the charge compressibility and the spin susceptibility exhibit the features of gapless excitations. The low-temperature phase has a long-range order, and the single-particle spectra are always gapped, while the charge and spin excitations are gapless in the strong interaction regime. In the fractionalized long-range ordered phase both the charge compressibility and the spin susceptibility are universal scaling functions of temperature.

cond-mat.str-el↗

arXiv2018

Selective Kondo strong coupling in magnetic impurity flat-band lattices

The periodic Anderson impurity model on the Lieb lattice is studied by the slave-boson mean-field approximation in the strong interaction limit. The electron structure of conduction electrons on the Lieb lattice features both the band flatness and soft gap at low energy. With these features conduction electrons can form both the soft-gap and the molecular Kondo singlets with the magnetic impurities, and this leads to a competition between the soft-gap and the molecular Kondo effects in the lattice. We find a selective Kondo strong coupling, where at selected sites the magnetic impurities are strongly coupled to conduction electrons, and at the remaining sites they are decoupled from the lattice. The selective Kondo strong coupling occurs between the full local moment and the full strong coupling regimes, and it yields an effective lattice depletion. At low temperature the selection of the Kondo strong coupling is dominant at those lattice sites, where the local density of states of conduction electrons exhibits the flat-band feature, independently of the impurity parameters. Rich phase diagrams for different model parameters are obtained.

cond-mat.str-el↗

arXiv2018

Molecular Kondo effect in flat-band lattices

The Kondo effect of a single magnetic impurity embedded in the Lieb lattice is studied by the numerical renormalization group. When the band flatness is present in the local density of states, it quenches the participation of all dispersive electrons in the Kondo singlet formation, and reduces the many-body Kondo problem to a two-electron molecular Kondo problem. The two-electron analog of the many-body Kondo singlet, a quantum entanglement of two spins, is stable at low temperature, and the impurity contributions to thermodynamical and dynamical quantities are qualitatively different from that obtained in the conventional Kondo effect in systems without flat bands. The existence conditions of the molecular Kondo effect in narrow band systems are also discussed.

cond-mat.str-el↗

arXiv2016

Metallic ferromagnetism-insulating charge order transition in doped manganites

We show that an interplay of double exchange and impurity randomness can explain the competition between metal-ferromagnetic and insulating charge ordered states in doped manganites. The double exchange is simplified in the Ising type, whereas the randomness is modeled by the Falicov-Kimball binary distribution. The combined model is considered in a framework of dynamical mean-field theory. Using the Kubo-Greenwood formalism, the transport coefficients are explicitly expressed in terms of single particle spectral functions. Dividing the system into two sublattices we have pointed out a direct calculation to the checkerboard charge order parameter and the magnetizations. Numerical results show us that the checkerboard charge order can settle inside the ferromagnetic state at low temperature. An insulator-metal transition is also found at the point of the checkerboard charge order-ferromagnetic transition.

cond-mat.str-el↗

arXiv2015

Mott transitions in a three-component Falicov-Kimball model: A slave boson mean-field study

Metal-insulator transitions in a three-component Falicov-Kimball model are investigated within the Kotliar-Ruckenstein slave boson mean-field approach. The model describes a mixture of two interacting fermion atom species loaded into an optical lattice at ultralow temperature. One species is two-component atoms, which can hop in the optical lattice, and the other is single-component atoms, which are localized. Different correlation-driven metal-insulator transitions are observed depending on the atom filling conditions and local interactions. These metal-insulator transitions are classified by the band renormalization factors and the double occupancies of the atom species. The filling conditions and the critical value of the local interactions for these metal-insulator transitions are also analytically established. The obtained results not only are in good agreement with the dynamical mean-field theory for the three-component Falicov-Kimball model but also clarify the nature and properties of the metal-insulator transitions in a simple physics picture.

cond-mat.str-el↗

arXiv2015

Spin dynamics in paramagnetic diluted magnetic semiconductors

Microscopic properties of low-energy spin dynamics in diluted magnetic semiconductor are addressed in a framework of the Kondo lattice model including random distribution of magnetic dopants. Based on the fluctuation-dissipation theorem, we derive an explicit dependence of the spin diffusion coefficient on the single-particle Green function which is directly evaluated by dynamical mean-field theory. In the paramagnetic state, the magnetic scattering has been manifested to suppress spin diffusion. In agreement with other ferromagnet systems, we also point out that the spin diffusion in diluted magnetic semiconductors at small carrier concentration displays a monotonic $1/T$-like temperature dependence. By investigating the spin diffusion coefficient on a wide range of the model parameters, the obtained results have provided a significant scenario to understand the spin dynamics in the paramagnetic diluted magnetic semiconductors.

cond-mat.str-el↗

arXiv2015

The Kondo effect revisited: RG-improved perturbation theory based on the Schwinger-boson representation

Resorting to the Schwinger-boson representation for the description of a localized magnetic-impurity state, we develop an RG-improved (renormalization group) perturbation theory for the Kondo effect. This Schwinger-boson based RG-improved perturbation theory covers the whole temperature range from a decoupled local moment state to a local Fermi-liquid state through the crossover temperature regime, shown from the specific heat and spin susceptibility of the magnetic impurity. The Schwinger-boson based RG-improved perturbation theory makes the strong coupling fixed point at IR (infrared) accessible from the gaussian one at UV (ultraviolet) within the perturbation framework, regarded to be complementary to the Schwinger-boson based NCA (non-crossing approximation) self-consistent theory [Phys. Rev. Lett. {\bf 96}, 016601 (2006)]. The existence of the perturbatively accessible strong coupling fixed point implies the nature on the statistics of spinons, not determined by hands but chosen by the nature of strongly coupled systems.

cond-mat.str-el↗

arXiv2015

Mass-imbalance induced metal-insulator transition in a three-component Hubbard model

The effects of mass imbalance in a three-component Hubbard model are studied by the dynamical mean-field theory combined with exact diagonalization. The model describes a fermion-fermion mixture of two different particle species with a mass imbalance. One species is two-component fermion particles, and the other is single-component ones. The local interaction between particle species is considered isotropically. It is found that the mass imbalance can drive the mixture from insulator to metal. The insulator-metal transition is a species-selective-like transition of lighter mass particles and occurs only at commensurate particle densities and moderate local interactions. For weak and strong local interactions the mass imbalance does not change the ground state of the mixture.

cond-mat.str-el↗

arXiv2013

Correlation-driven phase transition in a Chern insulator

The phase transition driven by electron correlations in a Chern insulator is investigated within the dynamical mean-field theory. The Chern insulator is described by the Haldane model and the electron correlations are incorporated by introducing the short-range interaction between the itinerant electrons and localized fermions. In the preservation of the inversion symmetry, the electron correlations drive the system from the Chern insulator to a renormalized pseudogap metal, and then to the topologically trivial Mott insulator. When the inversion symmetry is broken, a charge ordering and a nontrivial Chern topological invariant coexist.

cond-mat.str-el↗

arXiv2013

Mott transitions in three-component Falicov-Kimball model

Metal-insulator transitions are studied within a three-component Falicov-Kimball model which mimics a mixture of one-component and two-component fermionic particles with local repulsive interactions in optical lattices. Within the model the two-component fermionic particles are able to hop in the lattice, while the one-component fermionic particles are localized. The model is studied by using the dynamical mean-field theory with exact diagonalization. Its homogeneous solutions establish Mott transitions for both commensurate and incommensurate fillings between one third and two thirds. At commensurate one third and two thirds fillings the Mott transition occurs for any density of hopping particles, while at incommensurate fillings the Mott transition can occur only for density one half of hopping particles. At half filling, depending on the repulsive interactions the reentrant effect of the Mott insulator is observed. As increasing local interaction of hopping particles, the first insulator-metal transition is continuous, whereas the second metal-insulator transition is discontinuous. The second metal-insulator transition crosses a finite region where both metallic and insulating phase coexist. At third filling the Mott transition is established only for strong repulsive interactions. A phase separation occurs together with the phase transition.

cond-mat.str-el↗

arXiv2011

A phase diagram for a topological Kondo insulating system

The discovery of topological insulators in non-interacting electron systems has motivated the community to search such topological states of matter in correlated electrons both theoretically and experimentally. In this paper we investigate a phase diagram for a topological Kondo insulating system, where an emergent "spin"-dependent Kondo effect gives rise to an inversion for heavy-fermion bands, responsible for a topological Kondo insulator. Resorting to the U(1) slave-boson mean-field analysis, we uncover an additional phase transition inside the Kondo insulating state in two dimensions, which results from the appearance of the topological Kondo insulator. On the other hand, we observe that the Kondo insulating state is distinguished into three insulating phases in three dimensions, identified with the weak topological Kondo insulator, the strong topological Kondo insulator, and the normal Kondo insulator, respectively, and classified by Z$_{2}$ topological indices. We discuss the possibility of novel quantum criticality between the fractionalized Fermi liquid and the topological Kondo insulator, where the band inversion occurs with the formation of the heavy-fermion band at the same time.

cond-mat.str-el↗

arXiv2011

Preformed heavy-electrons at the Quantum Critical Point in heavy fermion compounds

The existence of multiple energy scales is regarded as a signature of the Kondo breakdown mechanism for explaining the quantum critical behavior of certain heavy fermion compounds, like YbRh$_{2}$Si$_{2}$. The nature of the intermediate state between the heavy Fermi liquid and the quantum critical region, however, remains elusive. In this study we suggest an incoherent heavy-fermion scenario, where inelastic scattering with novel soft modes of the dynamical exponent $z = 3$ gives rise to non-Fermi liquid physics for thermodynamics and transport despite the formation of the heavy-fermion band. We discuss a crossover from $z = 3$ to $z = 1$ for quantum phase fluctuations.

cond-mat.str-el↗

arXiv2011

Competition between Kondo and RKKY correlations in the presence of strong randomness

We propose that competition between Kondo and magnetic correlations results in a novel universality class for heavy fermion quantum criticality in the presence of strong randomness. Starting from an Anderson lattice model with disorder, we derive an effective local field theory in the dynamical mean-field theory (DMFT) approximation, where randomness is introduced into both hybridization and Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions. Performing the saddle-point analysis in the U(1) slave-boson representation, we reveal its phase diagram which shows a quantum phase transition from a spin liquid state to a local Fermi liquid phase. In contrast with the clean limit of the Anderson lattice model, the effective hybridization given by holon condensation turns out to vanish, resulting from the zero mean value of the hybridization coupling constant. However, we show that the holon density becomes finite when variance of hybridization is sufficiently larger than that of the RKKY coupling, giving rise to the Kondo effect. On the other hand, when the variance of hybridization becomes smaller than that of the RKKY coupling, the Kondo effect disappears, resulting in a fully symmetric paramagnetic state, adiabatically connected with the spin liquid state of the disordered Heisenberg model. ......

cond-mat.str-el↗