scholarly journals UNCONVENTIONAL BOSE–EINSTEIN CONDENSATIONS BEYOND THE "NO-NODE" THEOREM

2009 ◽  
Vol 23 (01) ◽  
pp. 1-24 ◽  
Author(s):  
CONGJUN WU
Keyword(s):  
Time Reversal ◽  
Einstein Condensation ◽  
Time Reversal Symmetry ◽  
Many Body ◽  
New States ◽  
Break Time ◽  
Spin Texture ◽  
Bose Einstein ◽  
Complex Valued ◽  
State Wavefunctions

Feynman's "no-node" theorem states that the conventional many-body ground state wavefunctions of bosons in the coordinate representation are positive definite. This implies that time-reversal symmetry cannot be spontaneously broken. In this article, we review our progress in studying a class of new states of unconventional Bose–Einstein condensations beyond this paradigm. These states can either be the long-lived metastable states of ultracold bosons in high orbital bands in optical lattices as a result of the "orbital Hund's rule" interaction, or the ground states of spinful bosons with spin-orbit coupling linearly dependent on momentum. In both cases, Feynman's argument does not apply. The resultant many-body wavefunctions are complex-valued and thus break time-reversal symmetry spontaneously. Exotic phenomena in these states include the Bose–Einstein condensation at nonzero momentum, the ordering of orbital angular momentum moments, the half-quantum vortex, and the spin texture of skyrmions.

EXCITONS IN A HIGH MAGNETIC FIELD

1996 ◽  
Vol 10 (07) ◽  
pp. 729-775 ◽  
Author(s):  
ANDREI V. KOROLEV ◽  
MICHAEL A. LIBERMAN
Keyword(s):  
Magnetic Field ◽  
Binding Energy ◽  
High Magnetic Field ◽  
Bose Condensate ◽  
Einstein Condensation ◽  
Interacting Electrons ◽  
New States ◽  
The Stability ◽  
Bose Einstein ◽  
Quantization Representation

A high magnetic field, such that the distance between the Landau levels exceeds the binding energy of an exciton, gives an opportunity to create various new states of matter, i.e. exciton crystal, molecular compexes, Bose–Einstein condensation an exciton gas in a semiconductor, depending on the dimensionality of the system. We consider the problem of excitonic interaction in a semiconductor in its multi-electron formulation, starting from the second-quantization representation of the Hamiltonian of interacting electrons and holes in a high magnetic field. A system of excitons in its ground state in a high magnetic field is similar to a weakly non-ideal Bose gas; whereas the excited states may be strongly bounded. It is shown that different types of exciton complexes in a quasi-one-dimensional semiconductor quantum wire, from crystals to molecular chains, can be obtained both by varying the direction and intensity of the magnetic field and by changing the exciton density. The existence and the stability of the Bose condensate in a bulk semiconductor due to an essential decrease of the interaction between excitons and an increase of their binding energy in a high magnetic field are established at a high density of excitons. Existence of the built-in condensate of excitons in a broad density range significantly changes the excitation spectrum of coupled excitons and photons in a high magnetic field and results in a number of interesting optical phenomena.

ANTHONY LEGGETT: FEENBERG MEDALIST 1999 CONDENSED MATTER AS A TEST-BED FOR FUNDAMENTAL QUANTUM MECHANICS

2001 ◽  
Vol 15 (10n11) ◽  
pp. 1305-1311 ◽  
Author(s):  
C. E. CAMPBELL ◽  
J. W. CLARK ◽  
E. KROTSCHECK ◽  
L. P. PITAEVSKII
Keyword(s):  
Quantum Coherence ◽  
High Temperature Superconductivity ◽  
Einstein Condensation ◽  
Test Bed ◽  
Many Body ◽  
Atomic Systems ◽  
Liquid Theory ◽  
Macroscopic Quantum Coherence ◽  
Key Aspects ◽  
Bose Einstein

The Eugene Feenberg Medal is awarded to Anthony J. Leggett in recognition of his seminal contributions to Many-Body Physics, including the explanation of the remarkable properties of superfluid 3 He in the millikelvin regime, important results in Fermi-liquid theory applied to metals, fundamental new insights into macroscopic quantum coherence, elucidation of key aspects of high-temperature superconductivity, and pioneering studies of the implications of Bose-Einstein condensation in atomic systems.

Spin-Polarized Quantum Fluids and Solids

MRS Bulletin ◽  
1993 ◽  
Vol 18 (8) ◽  
pp. 38-43
Author(s):  
Kevin S. Bedell ◽  
Isaac F. Silvera ◽  
Neil S. Sullivan
Keyword(s):  
Magnetic Ordering ◽  
Quantum Fluids ◽  
Einstein Condensation ◽  
Many Body ◽  
Spin Polarized ◽  
Many Body Systems ◽  
The Rich ◽  
Bose Einstein ◽  
Physical Phenomena

The spin-polarized phases of the quantum fluids and solids, liquid 3He, solid 3He, and spin-aligned hydrogen have generated considerable excitement over the past fifteen years. The introduction of high magnetic fields (B ∼ 10–30 T) in conjunction with low temperatures (T ≲ 100 mK) has given rise to opportunities for exploring some of the new phases predicted for these materials. There is a broad range of physical phenomena that can be accessed in this regime of parameter space—unconventional superfluidity, unusual magnetic ordering, Bose-Einstein condensation and Kosterlitz-Thouless transitions, to name a few. This is most surprising since this plethora of complicated states of matter are present in some of the most uncomplicated materials. The rich variety of phases found in these materials are all examples of collective phenomena of quantum many-body systems, and they serve as prototypes for developing an understanding of magnetism and order/disorder processes in other systems, and for the design and characterization of new materials.

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