Heat transport in spin-boson systems near the thermal equilibrium is systematically investigated. An asymptotically exact expression for the thermal conductance in a low-temperature regime wherein ...transport is described via a co-tunneling mechanism is derived. This formula predicts the power-law temperature dependence of thermal conductance ∝ T 2 s + 1 for a thermal environment of spectral density with the exponent s. An accurate numerical simulation is performed using the quantum Monte Carlo method, and these predictions are confirmed for arbitrary thermal baths. Our numerical calculation classifies the transport mechanism, and shows that the non-interacting-blip approximation quantitatively describes thermal conductance in the incoherent transport regime.
mVMC (many-variable Variational Monte Carlo) is an open-source software package based on the variational Monte Carlo method applicable for a wide range of Hamiltonians for interacting fermion ...systems. In mVMC, we introduce more than ten thousands variational parameters and simultaneously optimize them by using the stochastic reconfiguration (SR) method. In this paper, we explain basics and user interfaces of mVMC. By using mVMC, users can perform the calculation by preparing only one input file of about ten lines for widely studied quantum lattice models, and can also perform it for general Hamiltonians by preparing several additional input files. We show the benchmark results of mVMC for the Hubbard model, the Heisenberg model, and the Kondo-lattice model. These benchmark results demonstrate that mVMC provides ground-state and low-energy-excited-state wave functions for interacting fermion systems with high accuracy.
Program title: mVMC
Program Files doi:http://dx.doi.org/10.17632/xhgyp6ncvt.1
Licensing provisions: GNU General Public License version 3
Programming language: C
External routines/libraries: MPI, BLAS, LAPACK, Pfapack, ScaLAPACK (optional)
Nature of problem: Physical properties (such as the charge/spin structure factors) of strongly correlated electrons at zero temperature.
Solution method: Application software based on the variational Monte Carlo method for quantum lattice model such as the Hubbard model, the Heisenberg model and the Kondo model.
Unusual features: It is possible to perform the highly-accurate calculations for ground states in a wide range of theoretical Hamiltonians in quantum many-body systems. In addition to the conventional orders such as magnetic and/or charge orders, user can treat the anisotropic superconductivities within the same framework. This flexibility is the main advantage of mVMC.
General relations for nonequilibrium spin transport at a magnetic junction between a normal metal and a ferromagnetic insulator are derived from the quantum fluctuation theorem. They include the ...extended Onsager relations between the spin conductance and the spin-current noise that hold for nonequilibrium states driven by an external current. These relations are valid for a general setup of spin Hall magnetoresistance (SMR) when the main contribution is due to the interfacial spin conductance. Unidirectional spin Hall magnetoresistance (UMR) in insulating ferromagnetic junctions can be understood in a similar way. Therefore, our work can provide a comprehensive viewpoint for understanding of SMR and UMR in insulating ferromagnetic junctions. Our result also predicts relations for higher-order coefficients with respect to the external current in terms of higher-order cumulants in a unified framework.
•General relations were derived from the fluctuation theorem for nonequilibrium spin transport at a normal-metal/ferromagnetic-insulator interface.•The obtained formulas include the extended Onsager relation that holds between the spin conductance and the spin-current noise.•Our results will attribute to comprehension of the unidirectional spin Hall magnetoresistance in insulating ferromagnetic junctions.
Amyotrophic lateral sclerosis (ALS) has its onset in middle age and is a progressive disorder characterized by degeneration of motor neurons of the primary motor cortex, brainstem and spinal cord. ...Most cases of ALS are sporadic, but about 10% are familial. Genes known to cause classic familial ALS (FALS) are superoxide dismutase 1 (SOD1), ANG encoding angiogenin, TARDP encoding transactive response (TAR) DNA-binding protein TDP-43 (ref. 4) and fused in sarcoma/translated in liposarcoma (FUS, also known as TLS). However, these genetic defects occur in only about 20-30% of cases of FALS, and most genes causing FALS are unknown. Here we show that there are mutations in the gene encoding optineurin (OPTN), earlier reported to be a causative gene of primary open-angle glaucoma (POAG), in patients with ALS. We found three types of mutation of OPTN: a homozygous deletion of exon 5, a homozygous Q398X nonsense mutation and a heterozygous E478G missense mutation within its ubiquitin-binding domain. Analysis of cell transfection showed that the nonsense and missense mutations of OPTN abolished the inhibition of activation of nuclear factor kappa B (NF- B), and the E478G mutation revealed a cytoplasmic distribution different from that of the wild type or a POAG mutation. A case with the E478G mutation showed OPTN-immunoreactive cytoplasmic inclusions. Furthermore, TDP-43- or SOD1-positive inclusions of sporadic and SOD1 cases of ALS were also noticeably immunolabelled by anti-OPTN antibodies. Our findings strongly suggest that OPTN is involved in the pathogenesis of ALS. They also indicate that NF- B inhibitors could be used to treat ALS and that transgenic mice bearing various mutations of OPTN will be relevant in developing new drugs for this disorder.
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