SU(2) slave-boson formulation of spin nematic states in S=1/2 frustrated ferromagnets (2009)
Shindou, Ryuichi, Momoi, Tsutomu
An SU(2) slave boson formulation of bond-type spin nematic orders is developed in frustrated ferromagnets, where the spin nematic states are described as the resonating spin-triplet valence bond...
Disorder effect on 3-dimensional $Z_2$ quantum spin Hall systems (2008)
Shindou, Ryuichi, Murakami, Shuichi
In this paper, we studied the nonmagnetic disorder effects onto the quantum critical point (QCP) which intervenes an ordinary insulator and the 3-dimensional $Z_2$ quantum spin Hall insulator. The...
Gradient expansion approach to multiple-band Fermi liquids (2007)
Shindou, Ryuichi, Balents, Leon
Promoted by the recent progress of Berry phase physics in spin galvanomagnetic communities, we develop a systematic derivation of the reduced Keldysh equation (RKE) which captures the low-energy...
Characterization of two-dimensional fermionic insulating states (2007)
Shindou, Ryuichi, Imura, Ken-Ichiro, Ogata, Masao
Inspired by the duality picture between superconductivity and insulator in two spatial dimension, we conjecture that the order parameter, suitable for characterizing 2D fermionic insulating state, is...
Effective Hamiltonians for some highly frustrated magnets (2006)
Bergman, Doron L., Shindou, Ryuichi, Fiete, Gregory A., Balents, Leon
In prior work, the authors developed a method of degenerate perturbation theory about the Ising limit to derive an effective Hamiltonian describing quantum fluctuations in a half-polarized...
Degenerate perturbation theory of quantum fluctuations in a pyrochlore antiferromagnet (2006)
Bergman, Doron L., Shindou, Ryuichi, Fiete, Gregory A., Balents, Leon
We study the effect of quantum fluctuations on the half-polarized magnetization plateau of a pyrochlore antiferromagnet. We argue that an expansion around the easy axis limit is appropriate for...
Mechanisms of degeneracy breaking in pyrochlore antiferromagnets (2006)
Bergman, Doron L., Shindou, Ryuichi, Fiete, Gregory A., Balents, Leon
Motivated by the low temperature magnetization curves of several spinel chromites, we theoretically study classical mechanisms of degeneracy lifting in pyrochlore antiferromagnets. Our main focus is...
Artificial electric field in Fermi Liquids (2006)
Shindou, Ryuichi, Balents, Leon
Based on the Keldysh formalism, we derive an effective Boltzmann equation for a quasi-particle associated with a particular Fermi surface in an interacting Fermi liquid. This provides a many-body...
Quantum effects in a half-polarized pyrochlore antiferromagnet (2005)
Bergman, Doron L., Shindou, Ryuichi, Fiete, Gregory A., Balents, Leon
We study quantum effects in a spin-3/2 antiferromagnet on the pyrochlore lattice in an external magnetic field, focusing on the vicinity of a plateau in the magnetization at half the saturation...
Shindou, Ryuichi, Imura, Ken-Ichiro
Motivated by a recent proposal on the possibility of observing a monopole in the band structure, and by an increasing interest on the role of Berry phase in spintronics, we studied the adiabatic...
In this paper, we propose the quantum spin pumping in quantum spin systems where an applied electric field ($E$) and magnetic field ($H$) cause a finite spin gap to its critical ground state. When...
Geometrical aspects of Gigantic Magneto-Electric effect and Quantum Pump (2003)
Shindou, Ryuichi, Nagaosa, Naoto
We study the Magneto-Electric (ME) effect from the viewpoint of the Berry phase connection and quantum adiabatic charge transport (QAPT). The linear response theory for the electronic polarization...
Theory of Excitonic States in CaB6 (2002)
Murakami, Shuichi, Shindou, Ryuichi, Nagaosa, Naoto, Mishchenko, Andrei S.
We study the excitonic states in CaB6 in terms of the Ginzburg-Landau theory. By minimizing the free energy and by comparing with experimental results, we identify two possible ground states with...
Orbital ferromagnetism and anomalous Hall effect in antiferromagnets on distorted fcc lattice (2001)
Shindou, Ryuichi, Nagaosa, Naoto
The Berry phase due to the spin wavefunction gives rise to the orbital ferromagnetism and anomalous Hall effect in the non-coplanar antiferromagnetic ordered state on face centered cubic (fcc)...
Theory of Ferromagnetism in Ca1-xLaxB6 (2001)
Murakami, Shuichi, Shindou, Ryuichi, Nagaosa, Naoto, Mishchenko, Andrei S.
Novel ferromagnetism in Ca$_{1-x}$La$_{x}$B$_6$ is studied in terms of the Ginzburg-Landau theory for excitonic order parameters, taking into account symmetry of the wavefunctions. We found that the...