Spin-neutral currents for spintronics

Electric currents carrying a net spin polarization are widely used in spintronics, whereas globally spin-neutral currents are expected to play no role in spin-dependent phenomena. Here we show that, in contrast to this common expectation, spin-independent conductance in compensated antiferromagnets and normal metals can be efficiently exploited in spintronics, provided their magnetic space group symmetry supports a non-spin-degenerate Fermi surface. Due to their momentum-dependent spin polarization, such antiferromagnets can be used as active elements in antiferromagnetic tunnel junctions (AFMTJs) and produce a giant tunneling magnetoresistance (TMR) effect. Using RuO2 as a representative compensated antiferromagnet exhibiting spin-independent conductance along the [001] direction but a non-spin-degenerate Fermi surface, we design a RuO2/TiO2/RuO2 (001) AFMTJ, where a globally spin-neutral charge current is controlled by the relative orientation of the Néel vectors of the two RuO2 electrodes, resulting in the TMR effect as large as ~500%. These results are expanded to normal metals which can be used as a counter electrode in AFMTJs with a single antiferromagnetic layer or other elements in spintronic devices. Our work uncovers an unexplored potential of the materials with no global spin polarization for utilizing them in spintronics.

A three Higgs doublet model with symmetry-suppressed flavour changing neutral currents

We construct a three-Higgs doublet model with a flavour non-universal U(1) × ℤ2 symmetry. That symmetry induces suppressed flavour-changing interactions mediated by neutral scalars. New scalars with masses below the TeV scale can still successfully negotiate the constraints arising from flavour data. Such a model can thus encourage direct searches for extra Higgs bosons in the future collider experiments, and includes a non-trivial flavour structure.

Deuteron disintegration by reactor antineutrinos

The existence of a new interaction involving the electron neutrino and the nucleons, which has received a convincing confirmation through a good agreement between the theoretical and experimental results concerning all observable processes with solar neutrinos, should also inevitably manifest itself in the deuteron disintegration by the neutral currents of reactor antineutrinos. The special attention is drawn to the problem of finding the neutron registration efficiency, discussed in the preparation of the experiment at the Sudbury Neutrino Observatory and in a number of special studies. Lessons are noted that can be learned from three long-standing experiments on the deuteron disintegration by reactor neutrinos.

Time-delayed electrons from neutral currents at the LHC

We investigate long-lived particles (LLPs) produced in pair from neutral currents and decaying into a displaced electron plus two jets at the LHC, utilizing the proposed minimum ionizing particle timing detector at CMS. We study two benchmark models: the R-parity-violating supersymmetry with the lightest neutralinos being the lightest supersymmetric particle and two different U(1) extensions of the standard model with heavy neutral leptons (HNLs). The light neutralinos are produced from the standard model Z-boson decays via small Higgsino components, and the HNLs arise from decays of a heavy gauge boson, Z′. By simulating the signal processes at the HL-LHC with the center-of-mass energy $$ \sqrt{s} $$ s = 14 TeV and integrated luminosity of 3 ab−1, our analyses indicate that the search strategy based on a timing trigger and the final state kinematics has the potential to probe the parameter space that is complementary to other traditional LLP search strategies such as those based on the displaced vertex.

Generic one-loop matching conditions for rare meson decays

Leptonic and semileptonic meson decays that proceed via flavour-changing neutral currents provide excellent probes of physics of the standard model and beyond. We present explicit results for the Wilson coefficients of the weak effective Lagrangian for these decays in any perturbative model in which these processes proceed via one-loop contributions. We explicitly show that our results are finite and gauge independent, and provide Mathematica code that implements our results in an easily usable form.