Electrical Detection of Ferroelectric-like Metals through Nonlinear Hall Effect

Ferroelectric-like metals are a relatively rare class of materials that have ferroelectric-like distortion and metallic conductivity. LiOsO$_3$ is the first demonstrated and the most investigated ferroelectric-like metal. The presence of free carriers makes them difficult to be studied by traditional ferroelectric techniques. In this paper, using the symmetry analysis and first-principles calculations, we demonstrate that the ferroelectric-like transition of LiOsO$_3$ can be probed by a kind of electrical transport method based on nonlinear Hall effect. The Berry curvature dipole exists in the ferroelectric-like phase, and it can lead to a measurable nonlinear Hall conductance with a conventional experimental setup. However, the symmetry of the paraelectric-like phase LiOsO$_3$ vanishes the Berry curvature dipole. The Berry curvature dipole shows a strong dependence on the polar displacement, which might be helpful for the detection of polar order. The nonlinear Hall effect provides an effective method for the detection of phase transition in the study of the ferroelectric-like metals and promotes them to be applied in the ferroelectric-like electronic devices

Electrical detection of ferroelectriclike metals through the nonlinear Hall effect

Ferroelectriclike metals are a relatively rare class of materials that have ferroelectriclike distortion and metallic conductivity. LiOsO3 is the first demonstrated and the most investigated ferroelectriclike metal. The presence of free carriers makes them difficult to be studied by traditional ferroelectric techniques. In this paper, using symmetry analysis and first-principles calculations, we demonstrate that the ferroelectriclike transition of LiOsO3 can be probed by a kind of electrical transport method based on nonlinear Hall effect. The Berry curvature dipole exists in the ferroelectriclike phase and it can lead to a measurable nonlinear Hall conductance with a conventional experimental setup. However, the symmetry of the paraelectriclike phase LiOsO3 vanishes the Berry curvature dipole. The Berry curvature dipole shows a strong dependence on the polar displacement, which might be helpful for the detection of polar order. The nonlinear Hall effect provides an effective method for the detection of phase transition in the study of the ferroelectriclike metals and promotes them to be applied in ferroelectriclike electronic devices

Constraints on flavor-changing neutral-current HtqHtq couplings from the signal of tHtH associated production with QCD next-to-leading order accuracy at the LHC

We study a generic Higgs boson and a top quark associated production via model-independent flavor-changing neutral-current couplings at the LHC, including complete QCD next-to-leading order (NLO) corrections to the production and decay of the top quark and the Higgs boson. We find that QCD NLO corrections can increase the total production cross sections by about 48.9% and 57.9% for the $Htu$ and $Htc$ coupling induced processes at the LHC, respectively. After kinematic cuts are imposed on the decay products of the top quark and the Higgs boson, the QCD NLO corrections are reduced to 11% for the $Htu$ coupling induced process and almost vanish for the $Htc$ coupling induced process. Moreover, QCD NLO corrections reduce the dependence of the total cross sections on the renormalization and factorization scales. We also discuss signals of the $tH$ associated production with the decay mode t \rightarrow bl^{+}E \slash_{T}, H \rightarrow b\bar{b} and $t\bar{t}$ production with the decay mode \bar{t} \rightarrow H\bar{q}, t\rightarrow bl^{+}E \slash_{T}. Our results show that, in some parameter regions, the LHC may observe the above signals at the $5\sigma$ level. Otherwise, the upper limits on the FCNC $Htq$ couplings can be set.Comment: 28 pages, 14 figures, 5 tables; version published in PR

Amide Activation by Tf2O: Reduction of Amides to Amines by NaBH4 under Mild Conditions

An expeditious and practical method for the reduction of amides to amines is reported. The method is consisted of activation of amides with Tf2O followed by reduction with sodium borohydride in THF at room temperature. Various amides/lactams gave the corresponding amines in good to excellent yields, even with hindered amides and secondary amides. This method also presents other advantages such as TBDPS-group tolerance, short reaction time, simple workup and purification procedure.NSF of China [20832005]; National Basic Research Program (973 Program) of China [2010CB833200