573 citations · 1.3k across the 33 of their papers we have counts for
33 papers
Quantum Criticality in Open Quantum Spin Chains with Nonreciprocity
Samuel E. Begg, Ryo Hanai
We investigate the impact of nonreciprocity on universality and critical phenomena in open quantum interacting many-body systems. Nonreciprocal open quantum systems often have an e…
Squeezing stationary distributions of stochastic chemical reaction systems
Yuji Hirono, Ryo Hanai
Stochastic modeling of chemical reaction systems based on master equations has been an indispensable tool in physical sciences. In the long-time limit, the properties of these syst…
Non-reciprocal frustration: time crystalline order-by-disorder phenomenon and a spin-glass-like state
Ryo Hanai
Active systems are comprised of constituents with interactions that are generically non-reciprocal in nature. Such non-reciprocity often gives rise to situations where conflicting…
Exceptional points in nonlinear and stochastic dynamics
Cheyne Weis, Michel Fruchart, Ryo Hanai +3
We study a class of bifurcations generically occurring in dynamical systems with non-mutual couplings ranging from models of coupled neurons to predator-prey systems and non-linear…
Proposed Fermi-surface reservoir-engineering and application to realizing unconventional Fermi superfluids
Taira Kawamura, Ryo Hanai, Yoji Ohashi
We theoretically propose an idea based on reservoir engineering to process the structure of a Fermi edge to split into multiple Fermi edges, so as to be suitable for the state whic…
Proposed Fermi-surface reservoir-engineering and application to realizing unconventional Fermi superfluids in a driven-dissipative non-equilibrium Fermi gas
Taira Kawamura, Ryo Hanai, Yoji Ohashi
We develop a theory to describe the dynamics of a driven-dissipative many-body Fermi system, to pursue our proposal to realize exotic quantum states based on reservoir engineering.…
Intrinsic mechanisms for drive-dependent Purcell decay in superconducting quantum circuits
Ryo Hanai, Alexander McDonald, Aashish Clerk
We develop a new approach to understanding intrinsic mechanisms that cause the -decay rate of a multi-level superconducting qubit to depend on the photonic population of a cou…
Non-equilibrium stationary states of quantum non-Hermitian lattice models
Alexander McDonald, Ryo Hanai, Aashish A. Clerk
We show how generic non-Hermitian tight-binding lattice models can be realized in an unconditional, quantum-mechanically consistent manner by constructing an appropriate open quant…
Non-reciprocal phase transitions
Michel Fruchart, Ryo Hanai, Peter B. Littlewood +1
Out of equilibrium, the lack of reciprocity is the rule rather than the exception. Non-reciprocal interactions occur, for instance, in networks of neurons, directional growth of in…
Direct observation of the quantum-fluctuation driven amplitude mode in a microcavity polariton condensate
Mark Steger, Ryo Hanai, Alexander Orson Edelman +7
The Higgs amplitude mode is a collective excitation studied and observed in a broad class of matter, including superconductors, charge density waves, antiferromagnets, 3He p-wave s…
Non-equilibrium strong-coupling theory for a driven-dissipative ultracold Fermi gas in the BCS-BEC crossover region
Taira Kawamura, Ryo Hanai, Daichi Kagamihara +2
We theoretically investigate strong-coupling properties of an ultracold Fermi gas in the BCS-BEC crossover regime in the non-equilibrium steady state, being coupled with two fermio…
Critical fluctuations at a many-body exceptional point
Ryo Hanai, Peter B. Littlewood
Critical phenomena arise ubiquitously in various context of physics, from condensed matter, high energy physics, cosmology, to biological systems, and consist of slow and long-dist…
Non-Hermitian phase transition from a polariton Bose-Einstein condensate to a photon laser
Ryo Hanai, Alexander Edelman, Yoji Ohashi +1
We propose a novel mechanism for a nonequilibrium phase transition in a -broken phase of an electron-hole-photon system, from a Bose-Einstein condensate of polaritons to a ph…
Photoluminescence and gain/absorption spectra of a driven-dissipative electron-hole-photon condensate
Ryo Hanai, Peter B. Littlewood, Yoji Ohashi
We investigate theoretically nonequilibrium effects on photoluminescence and gain/absorption spectra of a driven-dissipative exciton-polariton condensate, by employing the combined…
Pseudogap regime of a two-dimensional uniform Fermi gas
Morio Matsumoto, Ryo Hanai, Daisuke Inotani +1
We investigate pseudogap phenomena in a two-dimensional Fermi gas. Including pairing fluctuations within a self-consistent -matrix approximation, we determine the pseudogap temp…
Spin susceptibility and effects of a harmonic trap in the BCS-BEC crossover regime of an ultracold Fermi gas
Hiroyuki Tajima, Ryo Hanai, Yoji Ohashi
We theoretically investigate magnetic properties of a trapped ultracold Fermi gas. Including pairing fluctuations within the framework of an extended -matrix approximation (ETMA…
Single-particle Excitations and Effects of Hetero-pairing Fluctuations in a Bose-Fermi Mixture with a Feshbach Resonance
Digvijay Kharga, Daisuke Inotani, Ryo Hanai +1
We theoretically investigate normal-state properties of a gas mixture of single-component bosons and fermions with a hetero-nuclear Feshbach resonance. Including strong hetero-pair…
Strong-coupling corrections to ground-state properties of a superfluid Fermi gas
Hiroyuki Tajima, Pieter van Wyk, Ryo Hanai +4
We theoretically present an economical and convenient way to study ground-state properties of a strongly interacting superfluid Fermi gas. Our strategy is that complicated strong-c…
Local Photoemission Spectra and Effects of Spatial Inhomogeneity in the BCS-BEC Crossover Regime of a Trapped Ultracold Fermi Gas
Miki Ota, Hiroyuki Tajima, Ryo Hanai +2
We theoretically investigate single particle excitations in the BCS (Bardeen-Cooper-Schrieffer)-BEC (Bose-Einstein-Condensation) crossover regime of an ultracold Fermi gas. Includi…
Pseudogap phenomena near the BKT transition of a two-dimensional ultracold Fermi gas in the crossover region
Morio Matsumoto, Ryo Hanai, Daisuke Inotani +1
We investigate strong-coupling properties of a two-dimensional ultracold Fermi gas in the normal phase. In the three-dimensional case, it has been shown that the so-called pseudoga…
Triplet pair amplitude in a trapped -wave superfluid Fermi gas with broken spin rotation symmetry. II. Three dimensional continuum case
Daisuke Inotani, Ryo Hanai, Yoji Ohashi
We extend our recent work [Y. Endo et. al., Phys. Rev. 92, 023610 (2015)] for a parity-mixing effect in a model two-dimensional lattice fermions to a realistic three-dimensional ul…
Dynamical instability of a driven-dissipative electron-hole condensate in the BCS-BEC-crossover region
Ryo Hanai, Peter B. Littlewood, Yoji Ohashi
We present a stability analysis on a driven-dissipative electron-hole condensate in the BCS (Bardeen-Cooper-Schrieffer)-BEC (Bose-Einstein-condensation)-crossover region. Extending…
Specific heat and effects of pairing fluctuations in the BCS-BEC crossover regime of an ultracold Fermi gas
Pieter van Wyk, Hiroyuki Tajima, Ryo Hanai +1
We investigate the specific heat at constant volume in the BCS (Bardeen-Cooper-Schrieffer)-BEC (Bose-Einstein condensation) crossover regime of an ultracold Fermi gas above t…
Spin susceptibility and effects of inhomogeneous strong pairing fluctuations in a trapped ultracold Fermi gas
Hiroyuki Tajima, Ryo Hanai, Yoji Ohashi
We theoretically investigate magnetic properties of a unitary Fermi gas in a harmonic trap. Including strong pairing fluctuations within the framework of an extended -matrix app…