Frontiers of Physics

ISSN 2095-0462

ISSN 2095-0470(Online)

CN 11-5994/O4

邮发代号 80-965

2018 Impact Factor: 2.483

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Possible phase transition of anisotropic frustrated Heisenberg model at finite temperature
Ai-Yuan Hu, Lin Wen, Guo-Pin Qin, Zhi-Min Wu, Peng Yu, Yu-Ting Cui
Frontiers of Physics    2019, 14 (5): 53601-null.   https://doi.org/10.1007/s11467-019-0895-2
摘要   PDF (1645KB)

The frustrated spin-1/2 J1aJ1bJ2 antiferromagnet with anisotropy on the two-dimensional square lattice was investigated, where the parameters J1aand J1b represent the nearest neighbor exchanges and along the x and y directions, respectively. J2 represents the next-nearest neighbor exchange. The anisotropy includes the spatial and exchange anisotropies. Using the double-time Green’s function method, the effects of the interplay of exchanges and anisotropy on the possible phase transition of the Néel state and stripe state were discussed. Our results indicated that, in the case of anisotropic parameter 0≤η<1, the Néel and stripe states can exist and have the same critical temperature as long as J2 = J1b/2. Under such parameters, a first-order phase transformation between the Néel and stripe states can occur below the critical point. For J2J1b/2, our results indicate that the Néel and stripe states can also exist, while their critical temperatures differ. When J2>J1b/2, a first-order phase transformation between the two states may also occur. However, for J2<J1b/2, the Néel state is always more stable than the stripe state.

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Large magnetocaloric effect in van der Waals crystal CrBr3
Xiaoyun Yu, Xiao Zhang, Qi Shi, Shangjie Tian, Hechang Lei, Kun Xu, Hideo Hosono
Frontiers of Physics    2019, 14 (4): 43501-null.   https://doi.org/10.1007/s11467-019-0883-6
摘要   PDF (2503KB)

We study the magnetocaloric effect (MCE) in van der Waals (vdW) crystal CrBr3. Bulk CrBr3 exhibits a second-order paramagnetic-ferromagnetic phase transition with TC = 33 K. The maximum magnetic entropy change −ΔSM near TC is about 7.2 J·kg−1·K−1 with the maximum adiabatic temperature change ΔTmaxad = 2.37 K and the relative cooling power RCP= 191.5 J·kg−1 at μ0H = 5 T, all of which are remarkably larger than those in CrI3. These results suggest that the vdW crystal CrBr3 is a promising candidate for the low-dimensional magnetic refrigeration in low temperature region.

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Dynamical characteristic of measurement uncertainty under Heisenberg spin models with Dzyaloshinskii–Moriya interactions
Ying-Yue Yang, Wen-Yang Sun, Wei-Nan Shi, Fei Ming, Dong Wang, Liu Ye
Frontiers of Physics    2019, 14 (3): 31601-null.   https://doi.org/10.1007/s11467-018-0880-1
摘要   PDF (2112KB)

The dynamics of measurement’s uncertainty via entropy for a one-dimensional Heisenberg XY Z mode is examined in the presence of an inhomogeneous magnetic field and Dzyaloshinskii–Moriya (DM) interaction. It shows that the uncertainty of interest is intensively in connection with the filed’s temperature, the direction-oriented coupling strengths and the magnetic field. It turns out that the stronger coupling strengths and the smaller magnetic field would induce the smaller measurement’s uncertainty of interest within the current spin model. Interestingly, we reveal that the evolution of the uncertainty exhibits quite different dynamical behaviors in antiferromagnetic (Ji>0) and ferromagnetic (Ji<0) frames. Besides, an analytical solution related to the systematic entanglement (i.e., concurrence) is also derived in such a scenario. Furthermore, it is found that the DM-interaction is desirably working to diminish the magnitude of the measurement’s uncertainty in the region of high-temperature. Finally, we remarkably offer a resultful strategy to govern the entropy-based uncertainty through utilizing quantum weak measurements, being of fundamentally importance to quantum measurement estimation in the context of solid-state-based quantum information processing and computation.

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Bohm’s approach to quantum mechanics: Alternative theory or practical picture?
A. S. Sanz
Frontiers of Physics    2019, 14 (1): 11301-.   https://doi.org/10.1007/s11467-018-0853-4
摘要   PDF (7170KB)

Since its inception Bohmian mechanics has been generally regarded as a hidden-variable theory aimed at providing an objective description of quantum phenomena. To date, this rather narrow conception of Bohm’s proposal has caused it more rejection than acceptance. Now, after 65 years of Bohmian mechanics, should still be such an interpretational aspect the prevailing appraisal? Why not favoring a more pragmatic view, as a legitimate picture of quantum mechanics, on equal footing in all respects with any other more conventional quantum picture? These questions are used here to introduce a discussion on an alternative way to deal with Bohmian mechanics at present, enhancing its aspect as an efficient and useful picture or formulation to tackle, explore, describe and explain quantum phenomena where phase and correlation (entanglement) are key elements. This discussion is presented through two complementary blocks. The first block is aimed at briefly revisiting the historical context that gave rise to the appearance of Bohmian mechanics, and how this approach or analogous ones have been used in different physical contexts. This discussion is used to emphasize a more pragmatic view to the detriment of the more conventional hidden-variable (ontological) approach that has been a leitmotif within the quantum foundations. The second block focuses on some particular formal aspects of Bohmian mechanics supporting the view presented here, with special emphasis on the physical meaning of the local phase field and the associated velocity field encoded within the wave function. As an illustration, a simple model of Young’s two-slit experiment is considered. The simplicity of this model allows to understand in an easy manner how the information conveyed by the Bohmian formulation relates to other more conventional concepts in quantum mechanics. This sort of pedagogical application is also aimed at showing the potential interest to introduce Bohmian mechanics in undergraduate quantum mechanics courses as a working tool rather than merely an alternative interpretation.

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Lattice quantum chromodynamics and baryon-baryon interactions
Tetsuo Hatsuda
Frontiers of Physics    2018, 13 (6): 132105-.   https://doi.org/10.1007/s11467-018-0829-4
摘要   PDF (2012KB)

After briefly reviewing the theoretical concepts and numerical methods in lattice QCD, recent simulation results of the hadron masses and hadron interactions with nearly physical quark masses are presented. Special emphasis is placed on the baryon-baryon interactions on the basis of the HAL QCD method where the integro-differential equation for the equal-time Nambu–Bethe–Salpeter amplitude plays a key role to bridge a gap between the multi-baryon correlation and the scattering observable such as the phase shift.

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Logic Bell state concentration with parity check measurement
Jiu Liu, Lan Zhou, Wei Zhong, Yu-Bo Sheng
Frontiers of Physics    2019, 14 (2): 21601-.   https://doi.org/10.1007/s11467-018-0866-z
摘要   PDF (3241KB)

Logic qubit plays an important role in current quantum communication. In this paper, we propose an efficient entanglement concentration protocol (ECP) for a new kind of logic Bell state, where the logic qubit is the concatenated Greenber–Horne–Zeilinger (C-GHZ) state. Our ECP relies on the nondemolition polarization parity check (PPC) gates constructed with cross-Kerr nonlinearity, and can distill one pair of maximally entangled logic Bell state from two same pairs of less-entangled logic Bell states. Benefit from the nondemolition PPC gates, the concentrated maximally entangled logic Bell state can be remained for further application. Moreover, our ECP can be repeated to further concentrate the less-entangled logic Bell state. By repeating the ECP, the total success probability can be effectively increased. Based on above features, this ECP may be useful in future long-distance quantum communication.

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Thermoelectricity in B80-based single-molecule junctions: First-principles investigation
Ying-Xiang Zhen, Ming Yang, Rui-Ning Wang
Frontiers of Physics    2019, 14 (2): 23603-.   https://doi.org/10.1007/s11467-018-0865-0
摘要   PDF (1506KB)

Thermoelectricity is a thermorelated property that is of great importance in single-molecule junctions. The electrical conductance (σ), electron-derived thermal conductance (κel) and Seebeck coefficient (S) of B80-based single-molecule junctions are investigated by using density functional theory in combination with non-equilibrium Green’s function. When the distance between the left/right electrodes is 11.4 Å, the relationship between σ and κel obeys the Wiedemann–Franz law very well because of the strong hybridization between B80 molecular orbitals and the surface states of Au electrodes. Furthermore, the calculated Lorenz number is close to the famous value in metal or degenerate semiconductors. In addition, S is only –19.09 μV/K at 300 K, thus leading to the smaller electron’s thermoelectric figure of merit (ZelT = S2σT/κel). Interestingly, the strain and chemical potential can modulate B80-based single-molecule junctions from n-type to p-type when the compressive strain reaches –0.6 Å or the chemical potential shifts to –0.16 eV. This might be attributed that S reflects the asymmetry in the electrical conductance with respect to the chemical potential and is proportional to the slopes of the transmission spectrum.

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Practical pulse engineering: Gradient ascent without matrix exponentiation
Gaurav Bhole, Jonathan A. Jones
Frontiers of Physics    2018, 13 (3): 130312-.   https://doi.org/10.1007/s11467-018-0791-1
摘要   PDF (140KB)

Since 2005, there has been a huge growth in the use of engineered control pulses to perform desired quantum operations in systems such as nuclear magnetic resonance quantum information processors. These approaches, which build on the original gradient ascent pulse engineering algorithm, remain computationally intensive because of the need to calculate matrix exponentials for each time step in the control pulse. In this study, we discuss how the propagators for each time step can be approximated using the Trotter–Suzuki formula, and a further speedup achieved by avoiding unnecessary operations. The resulting procedure can provide substantial speed gain with negligible costs in the propagator error, providing a more practical approach to pulse engineering.

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Dynamics of coherence-induced state ordering under Markovian channels
Long-Mei Yang, Bin Chen, Shao-Ming Fei, Zhi-Xi Wang
Frontiers of Physics    2018, 13 (5): 130310-.   https://doi.org/10.1007/s11467-018-0780-4
摘要   PDF (6459KB)

We study the dynamics of coherence-induced state ordering under incoherent channels, particularly four specific Markovian channels: amplitude damping channel, phase damping channel, depolarizing channel and bit flit channel for single-qubit states. We show that the amplitude damping channel, phase damping channel, and depolarizing channel do not change the coherence-induced state ordering by l1 norm of coherence, relative entropy of coherence, geometric measure of coherence, and Tsallis relative α-entropies, while the bit flit channel does change for some special cases.

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