| Autor: |
J H Zou, T Liu, M Feng, W L Yang, C Y Chen, J Twamley |
| Jazyk: |
angličtina |
| Rok vydání: |
2013 |
| Předmět: |
|
| Zdroj: |
New Journal of Physics, Vol 15, Iss 12, p 123032 (2013) |
| Druh dokumentu: |
article |
| ISSN: |
1367-2630 |
| DOI: |
10.1088/1367-2630/15/12/123032 |
| Popis: |
Quantum phase transitions (QPTs) describe when a many-body quantum system displays non-analytic behavior associated with a discontinuous change in a property of the ground state as a parameter is varied. The QPT in prototypical Dicke model is difficult to reach experimentally as the spin–field coupling strength must be quite large. In this work we describe a new model—the off-resonant Tavis–Cummings model where we drive the common mode, and discover a new type of QPT at quite low coupling strengths which are comparable with the geometric mean of the atomic and field detunings $\lambda \sim \lambda _{\mathrm { c}}\equiv \sqrt {\Delta _{\mathrm { a}}\Delta _{\mathrm { c}}}$ . Through analytic methods we demonstrate this QPT for both finite and infinite numbers of spins and show that |〈 J _x ( J _z )〉|/( N /2) ∼ | λ / λ _c − 1| ^γ ^x_x ^( ^γ ^z_z ^) and 〈 a ^† a 〉/ N ∼ | λ / λ _c − 1| ^γ ^a_a for λ ⩾ λ _c , with critical exponents γ _x ≈ 1/2, γ _z ≈ 1 and γ _a ≈ 1. We show that this QPT can be immediately observed by laboratory cavity-QED setups such as Bose–Einstein condensate in optical cavity and superconducting circuit-QED as well as a line of trapped ultracold ions. |
| Databáze: |
Directory of Open Access Journals |
| Externí odkaz: |
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