Periodic dynamics of fermionic superfluids in the BCS regime

Roy, Analabha; Dasgupta, Ranjan; Modak, S; Das, Arnab; Sengupta, K.

doi:10.1088/0953-8984/25/20/205703

Cited by 5 publications

(13 citation statements)

References 64 publications

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“…One of the key ingredients in these magnetic solids is the existence of a first-order magnetostructural phase transition which occurs not only in the Heusler alloys, which have been discussed here, but determines the physics in a series of other magnetic solids [74]. Strongly related to the martensitic/magnetostructural transition is the possibility of a kinetically arrested first-order transition which leads to a glass-like non-equilibrium phenomenon: a magnetic-cluster-spin glass has unequivocally been evidenced in Ni-Co-Mn-Sn Heusler alloy by small-angle neutron-scattering experiments [75].…”

Section: Discussionmentioning

confidence: 98%

Interacting magnetic cluster‐spin glasses and strain glasses in Ni–Mn based Heusler structured intermetallics

Entel

Gruner

Comtesse

et al. 2014

Physica Status Solidi (b)

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Magnetic Ni–Mn based Heusler intermetallics show complex magnetic behavior in connection with martensitic transformations (see, for instance, the phase diagram of Ni–Co–Mn–Sn on the right‐hand side). The cubic austenitic phase at high temperature shows long‐range ferromagnetic order which can considerably be weakened by the appearance of competing antiferromagnetic interactions which are induced by Mn excess and chemical disorder. With decreasing temperature a martensitic/magnetostructural transformation takes place from cubic to non‐modulated/modulated tetragonal/monoclinic or orthorhombic structure, where long‐range ferromagnetic order can no longer be maintained, leading to superparamagnetic behavior. At still lower temperatures superparamagnetism changes to superspin glass because of strong competition of ferromagnetic and antiferromagnetic interactions and chemical disorder. In addition, disorder and local structural distortions can lead to strain glass in austenite, as observed for some non‐magnetic martensitic systems. The magnetic intermetallics are of technological importance in view of their functional properties involving magnetic shape‐memory and exchange‐bias effects as well as magnetocaloric effects. The ‘ferroic cooling’ is of particular relevance since it avoids the use of ozone‐depleting and greenhouse chemicals compared with conventional fluid‐compression technology. Experimental phase diagram of Ni50−x Cox Mn39 Sn11 for 0≤x≤10. Here, TC is the Curie temperature of austenite; at TM the system transforms to paramagnetic martensite and at TS to superparamagnetic martensite (SPM) and then to superspin‐glass martensite (SSG) at TP. The possible strain‐glass phases (labeled by question marks) are predicted because of kinetic arrest phenomena and local distortions associated with the magnetostructural transition and ergodicity breaking by field‐cooling/zero‐field‐cooling experiments.

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Section: Discussionmentioning

confidence: 98%

Interacting magnetic cluster‐spin glasses and strain glasses in Ni–Mn based Heusler structured intermetallics

Entel

Gruner

Comtesse

et al. 2014

Physica Status Solidi (b)

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“…al. [23] have computed the response of the system as it evolves in time, demonstrating that the BCS self-consistency condition introduces nonlinearities in the dynamics and shapes the long-time behavior of the fermions subjected to the drive. If the system is started from the state in Eq.…”

Section: Satisfiesmentioning

confidence: 99%

“…al. [23] . The possibility of performing a linear stability analysis around a texture state similar to that by Volkov and Kogan as mentioned in the previous paragraph is a subject of future study.…”

Section: Satisfiesmentioning

confidence: 99%

“…3 but for the non-self-consistent dynamics. Reproduced from [23] with permission from the authors. τ z k (t).…”

Section: Satisfiesmentioning

confidence: 99%

“…This mini-review article contains results from [12,13,[21][22][23]. Section III contains material from [23] that was presented by the author at the 2012 National Conference on Nonlinear Systems and Dynamics (Quantum Chaos minisymposium), held at the Indian Institute of Science Education and Research (IISER), Pune, India.…”

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Nonequilibrium dynamics of ultracold Fermi superfluids

Roy

2013

Eur. Phys. J. Spec. Top.

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The aim of this mini review is to survey the literature on the study of nonequilibrium dynamics of Fermi superfluids in the BCS and BEC limits, both in the single channel and dual channel cases. The focus is on mean field approaches to the dynamics, with specific attention drawn to the dynamics of the Ginzburg-Landau order parameters of the Fermi and composite Bose fields, as well as on the microscopic dynamics of the quantum degrees of freedom. The two approaches are valid approximations in two different time scales of the ensuing dynamics. The system is presumed to evolve during and/or after a quantum quench in the parameter space. The quench can either be an impulse quench with virtually instantaneous variation, or a periodic variation between two values. The literature for the order parameter dynamics, described by the time-dependent Ginzburg-Landau equations, is reviewed, and the works of the author in this area highlighted. The mixed phase regime in the dual channel case is also considered, and the dual order parameter dynamics of Fermi-Bose mixtures reviewed. Finally, the nonequilibrium dynamics of the microscopic degrees of freedom for the superfluid is reviewed for the self-consistent and non self-consistent cases. The dynamics of the former can be described by the Bogoliubov de-Gennes equations with the equilibrium BCS gap equation continued in time and self -consistently coupled to the BdG dynamics. The latter is a reduced BCS problem and can be mapped onto the dynamics of Ising and Kitaev models. This article reviews the dynamics of both impulse quenches in the Feshbach detuning, as well as periodic quenches in the chemical potential, and highlights the author's contributions in this area of research. I. INTRODUCTIONStudies of the coherent quantum dynamics of closed many body systems have gained considerable interest in the last two decades. This interest has been brought about by such states becoming experimentally accessible using ultracold atoms, cooled to near absolute zero temperatures by the use of optical molasses [1] , evaporative cooling [2], laser culling [3] , cavity QED methods [4] , and other experimental techniques. The experimental realization of the Bose Einstein condensate by Cornell, Ketterle and Weiman in 1995 [2] , as well as the realization of the Bosonic Superfluid Mott-Insulator transition by Greiner et. al. in 2002 [5] (theoretically predicted by Jaksch et. al. in 1998 [6] ), motivated strong theoretical interest in the coherent dynamics of ultracold bosons. Previously, the regimes where fermionic coherent dynamics can be realized were unattainable in either solid state systems or with ultracold atoms. The difficulties for ultracold atoms were eventually circumvented by experiments performed over the first decade of the 21 st century. Studies of fermionic atoms gained momentum after these experiments realized pure fermionic BCS states [7] , as well as the BCS-BEC crossover that was predicted theoretically a decade earlier [8] . The formation of Fermi superfluids were realized ...

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