$d$ band filling and magnetic phase separation in transition metal-doped Mn$_3$SnC

Orientation-dependent electric transport and band filling in hole co-doped epitaxial diamond films

Diamond, a well-known wide-bandgap insulator, becomes a low-temperature superconductor upon substitutional doping of carbon with boron. However, limited boron solubility and significant lattice disorder introduced by boron doping prevent attaining the theoretically-predicted high-temperature superconductivity. Here we present an alternative co-doping approach, based on the combination of ionic gating and boron substitution, in hydrogenated thin films epitaxially grown on (111)- and (110)-oriented single crystals. Gate-dependent electric transport measurements show that the effect of boron dopi…

掺杂有机超导体中的莫特物理

Mottness in a doped organic superconductor

本文通过压力调控掺杂有机超导体，发现超导增强与非费米液体行为共存，提出掺杂莫特绝缘体中强-弱关联间的量子相变图像。

Superconducting states of pure and doped graphene

We study the superconducting phases of the two-dimensional honeycomb lattice of graphene. We find two spin singlet pairing states, s-wave and an exotic $p+ip$ that is possible because of the special structure of the honeycomb lattice. At half filling, the $p+ip$ phase is gapless and superconductivity is a hidden order. We discuss the possibility of a superconducting state in metal coated graphene.

Filling dependence of the Mott transition in the degenerate Hubbard model

Describing the doped Fullerenes using a generalized Hubbard model, we study the Mott transition for different integer fillings of the t_1u band. We use the opening of the energy-gap E_g as a criterion for the transition. E_g is calculated as a function of the on-site Coulomb interaction U using fixed-node diffusion Monte Carlo. We find that for systems with doping away from half-filling the Mott transitions occurs at smaller U than for the half-filled system. We give a simple model for the doping dependence of the Mott transition.

掺杂费米哈伯德模型中金属-绝缘体交叉处热电输运系数的符号变化

Sign changes of the thermoelectric transport coefficient across the metal-insulator crossover in the doped Fermi Hubbard model

本研究通过量子蒙特卡罗模拟，发现掺杂费米哈伯德模型中塞贝克系数的额外符号变化由电荷隙控制，而非赝隙，且局域矩形成是异常热电输运的主要驱动因素。

Response of the lattice across the filling-controlled Mott metal-insulator transition of a rare earth titanate

The lattice response of a prototype Mott insulator, SmTiO3, to hole doping is investigated with atomic-scale spatial resolution. SmTiO3 films are doped with Sr on the Sm site with concentrations that span the insulating and metallic sides of the filling-controlled Mott metal-insulator transition (MIT). The GdFeO3-type distortions are investigated using an atomic resolution scanning transmission electron microscopy technique that can resolve small lattice distortions with picometer precision. We show that these distortions are gradually and uniformly reduced as the Sr concentration is increased…

Correlation effects on the doped triangular lattice in view of the physics of sodium-rich Na$_x$CoO$_2$

The peculiar correlation effects on the triangular lattice are studied by means of the rotationally invariant slave boson method in a cellular cluster approach. Hence nonlocal correlations are included in a short-range regime. Their impact for the single-band Hubbard model is studied at half filling, i.e., on the Mott transition, and with doping. Using the realistic band structure of Na$_x$CoO$_2$, we may also shed light on the cobaltate physics for $x$$\ge$1/3, with the in-plane transition from antiferromagnetic tendencies towards the onset of ferromagnetism for a finite Hubbard $U$.

Two Aspects of the Mott-Hubbard Transition in Cr-doped V_2O_3

The combination of bandstructure theory in the local density approximation with dynamical mean field theory was recently successfully applied to V$_2$O$_3$ -- a material which undergoes the f amous Mott-Hubbard metal-insulator transition upon Cr doping. The aim of this sh ort paper is to emphasize two aspects of our recent results: (i) the filling of the Mott-Hubbard gap with increasing temperature, and (ii) the peculiarities of the Mott-Hubbard transition in this system which is not characterized by a diver gence of the effective mass for the $a_{1g}$-orbital.

Band filling and interband scattering effects in MgB$_2$: C vs Al doping

We argue, based on band structure calculations and Eliashberg theory, that the observed decrease of $T_c$ of Al and C doped MgB$_2$ samples can be understood mainly in terms of a band filling effect due to the electron doping by Al and C. A simple scaling of the electron-phonon coupling constant $λ$ by the variation of the density of states as function of electron doping is sufficient to capture the experimentally observed behavior. Further, we also explain the long standing open question of the experimental observation of a nearly constant $π$ gap as function of doping by a compensation of th…

Robust superconductivity near constant temperature in rubidium-doped C$_{60}$

To establish the doping-dependent phase diagram in alkali-metal doped C$_{60}$, we synthesize Rb-doped C$_{60}$ samples with different stoichiometries by using the improved wet-chemistry technique. The doping levels determined from the Raman scattering spectra often show the appearance of three electrons corresponding to the band filling of three for the synthesized compounds no matter matter what dopants are used. The multiple phase coexistence with the unique Rb$_{3}$C$_{60}$ is identified from the refined x-ray diffraction patterns. The phase fraction of Rb$_{3}$C$_{60}$ is found to behave …

三层Hubbard模型中1/3填充附近超导电性的电子-空穴不对称性的涨落交换研究

Fluctuation exchange study on the electron-hole asymmetry of the superconductivity across 1/3 filling in the trilayer Hubbard model

利用涨落交换近似研究三层Hubbard模型，发现当在位U较小时超导近似电子-空穴对称，而U较大时出现不对称，空穴掺杂更有利于超导，归因于能带的不对称重整化。

单层 1T-TaSe$_{2-x}$Te$_{x}$ 中的自掺杂平带与自旋三重态超导性

Self-doped flat band and spin-triplet superconductivity in monolayer 1T-TaSe$_{2-x}$Te$_{x}$

理论研究表明，单层 1T-TaSe$_{2-x}$Te$_{x}$ 中 Te 配体取代可使费米能级平带自掺杂，并在磁性金属区间诱导 f 波与两类手征 p 波自旋三重态超导相。