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Register a new userHigh-spin to low-spin and orbital polarization transitions in multiorbital Mott systems
التحولات من الدوران العالي إلى الدوران المنخفض والتشديد الأوربيتي في النظم الموت المتعددة المناطق
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نحن ندرس تداخل التفرع المجال البلوري وربط هند في نموذج مؤثر بطريقتين المضمنة الفيزياء الأساسية للأنظمة مع إثنين من الإشعاعات أو الثقوب في غشاء e_g. نحن نستخدم الحقل المتحرك الموحد الموجز مع محلل عقار حديث الذي يمكنه الوصول إلى ربطات قوية ودرجات حرارة منخفضة. يتم حساب ملء المراكز الأوربيتالية ومواقع حدود المرحلة كدالة من الانزعاج الكولومبي والربط التبادل والتفرع المجال البلوري. نجد أن الربط هند يمكن أن يدفع النظام إلى مجال مغناطيسي موت جديد مع تحسس الأوربيتال الصفر. بعيدا عن الملء النصفي، يمكن للتفرع المجال البلوري أن يؤدي إلى حالة موت أوربيتالية محددة.
We study the interplay of crystal field splitting and Hund coupling in a two-orbital model which captures the essential physics of systems with two electrons or holes in the e_g shell. We use single site dynamical mean field theory with a recently developed impurity solver which is able to access strong couplings and low temperatures. The fillings of the orbitals and the location of phase boundaries are computed as a function of Coulomb repulsion, exchange coupling and crystal field splitting. We find that the Hund coupling can drive the system into a novel Mott insulating phase with vanishing orbital susceptibility. Away from half-filling, the crystal field splitting can induce an orbital selective Mott state.
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We study the thermally driven spin state transition in a two-orbital Hubbard model with crystal field splitting, which provides a minimal description of the physics of LaCoO3. We employ the dynamical mean-field theory with quantum Monte-Carlo impurity solver. At intermediate temperatures we find a spin disproportionated phase characterized by checkerboard order of sites with small and large spin moments. The high temperature transition from the disproportionated to a homogeneous phase is accompanied by vanishing of the charge gap. With the increasing crystal-field splitting the temperature range of the disproportionated phase shrinks and eventually disappears completely.
Spin textures in k-space arising from spin-orbit coupling in non-centrosymmetric crystals find numerous applications in spintronics. We present a mechanism that leads to appearance of k-space spin texture due to spontaneous symmetry breaking driven by electronic correlations. Using dynamical mean-field theory we show that doping a spin-triplet excitonic insulator provides a means of creating new thermodynamic phases with unique properties. The numerical results are interpreted using analytic calculations within a generalized double-exchange framework.
The orbital-selective Mott phase (OSMP) of multiorbital Hubbard models has been extensively analyzed before using static and dynamical mean-field approximations. In parallel, the properties of Block states (antiferromagnetically coupled ferromagnetic spin clusters) in Fe-based superconductors have also been much discussed. The present effort uses numerically exact techniques in one-dimensional systems to report the observation of Block states within the OSMP regime, connecting two seemingly independent areas of research, and providing analogies with the physics of Double-Exchange models.
We examine finite-temperature phase transitions in the two-orbital Hubbard model with different bandwidths by means of the dynamical mean-field theory combined with the continuous-time quantum Monte Carlo method. It is found that there emerges a peculiar slope-reversed first-order Mott transition between the orbital-selective Mott phase and the Mott insulator phase in the presence of Ising-type Hunds coupling. The origin of the slope-reversed phase transition is clarified by the analysis of the temperature dependence of the energy density. It turns out that the increase of Hunds coupling lowers the critical temperature of the slope-reversed Mott transition. Beyond a certain critical value of Hunds coupling the first-order transition turns into a finite-temperature crossover. We also reveal that the orbital-selective Mott phase exhibits frozen local moments in the wide orbital, which is demonstrated by the spin-spin correlation functions.
We analyze the electronic properties of interacting crystal field split three band systems. Using a rotationally invariant slave boson approach we analyze the behavior of the electronic mass renormalization as a function of the intralevel repulsion $U$, the Hunds coupling $J$, the crystal field splitting, and the number of electrons per site $n$. We first focus on the case in which two of the bands are identical and the levels of the third one are shifted by $Delta>0$ with respect to the former. We find an increasing quasiparticle mass differentiation between the bands, for system away from half-filling ($n=3$), as the Hubbard interaction $U$ is increased. This leads to orbital selective Mott transitions where either the higher energy band (for $4>n>3$) or the lower energy degenerate bands ($2<n<3$) become insulating for $U$ larger than a critical interaction $U_{c}(n)$. Away from the half-filled case $|n-3|gtrsim 0.3$ there is a wide range of parameters for $U<U_c(n)$ where the system presents a Hunds metal phase with the physics dominated by the local high spin multiplets. Finally, we study the fate of the $n=2$ Hunds metal as the energy splitting between orbitals is increased for different possible crystal distortions. We find a strong sensitivity of the Hunds metal regime to crystal fields due to the opposing effects of $J$ and the crystal field splittings on the charge distribution between the bands.
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