Ahmet Nihat Berker

Berker, Ahmet Nihat

Name Variants

Nihat Berker A.
BERKER, Ahmet Nihat
Ahmet Nihat, Berker
Berker,Ahmet Nihat
Berker, AHMET NIHAT
A. Berker
B.,Ahmet Nihat
Berker,A.N.
Berker, A.
Berker, Ahmet Nihat
Berker N.
Ahmet Nihat Berker
Ahmet Nihat BERKER
Berker, A. N.
B., Ahmet Nihat
AHMET NIHAT BERKER
A. N. Berker
BERKER, AHMET NIHAT
Berker A.
Berker, A. Nihat

Job Title

Prof. Dr.

Email Address

nihatberker@khas.edu.tr

ORCID ID

0000-0002-5172-2172

Scopus Author ID

6701401118

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Scholarly Output

27

Articles

27

Citation Count

0

Supervised Theses

0 Scholarly Output Search Results

Now showing 1 - 10 of 27

Citation Count: 8
First-order to second-order phase transition changeover and latent heats of q-state Potts models in d=2,3 from a simple Migdal-Kadanoff adaptation
(Amer Physical Soc, 2022) Devre, H. Yagiz; Berker, A. Nihat
The changeover from first-order to second-order phase transitions in q-state Potts models is obtained at q(c) = 2 in spatial dimension d = 3 and essentially at q(c) = 4 in d = 2, using a physically intuited simple adaptation of the Migdal-Kadanoff renormalization-group transformation. This simple procedure yields the latent heats at the first-order phase transitions. In both d = 2 and 3, the calculated phase transition temperatures, respectively compared with the exact self-duality and Monte Carlo results, are dramatically improved. The method, when applied to a slab of finite thickness, yields dimensional crossover.
Citation Count: 3
Electric-field induced phase transitions in capillary electrophoretic systems
(Aip Publishing, 2021) Kaygusuz, Hakan; Erim, F. Bedia; Berker, A. Nihat
The movement of particles in a capillary electrophoretic system under electroosmotic flow was modeled using Monte Carlo simulation with the Metropolis algorithm. Two different cases with repulsive and attractive interactions between molecules were taken into consideration. Simulation was done using a spin-like system, where the interactions between the nearest and second closest neighbors were considered in two separate steps of the modeling study. A total of 20 different cases with different rates of interactions for both repulsive and attractive interactions were modeled. The movement of the particles through the capillary is defined as current. At a low interaction level between molecules, a regular electroosmotic flow is obtained; on the other hand, with increasing interactions between molecules, the current shows a phase transition behavior. The results also show that a modular electroosmotic flow can be obtained for separations by tuning the ratio between molecular interactions and electric field strength.
Citation Count: 0
Metastable Potts droplets
(AMER PHYSICAL SOC, 2021-03) Artun, E. Can; Berker, A. Nihat
The existence and limits of metastable droplets have been calculated using finite-system renormalization-group theory, for q-state Potts models in spatial dimension d = 3. The dependence of the droplet critical sizes on magnetic field, temperature, and number of Potts states q has been calculated. The same method has also been used for the calculation of hysteresis loops across first-order phase transitions in these systems. The hysteresis loop sizes and shapes have been deduced as a function of magnetic field, temperature, and number of Potts states q. The uneven appearance of asymmetry in the hysteresis loop branches has been noted. The method can be extended to criticality and phase transitions in metastable phases, such as in surface-adsorbed systems and water.
Citation Count: 0
Axial, planar-diagonal, body-diagonal fields on the cubic-spin spin glass in d=3: A plethora of ordered phases under finite fields
(Amer Physical Soc, 2024) Artun, E. Can; Sarman, Deniz; Berker, A. Nihat
A nematic phase, previously seen in the d = 3 classical Heisenberg spin-glass system, occurs in the n-component cubic-spin spin-glass system, between the low-temperature spin-glass phase and the hightemperature disordered phase, for number of spin components n >= 3, in spatial dimension d = 3, thus constituting a liquid-crystal phase in a dirty (quenched-disordered) magnet. Furthermore, under application of a variety of uniform magnetic fields, a veritable plethora of phases is found. Under uniform magnetic fields, 17 different phases and two spin-glass phase diagram topologies (meaning the occurrences and relative positions of the many phases), qualitatively different from the conventional spin-glass phase diagram topology, are seen. The chaotic rescaling behaviors and their Lyapunov exponents are calculated in each of these spin-glass phase diagram topologies. These results are obtained from renormalization-group calculations that are exact on the d = 3 hierarchical lattice and, equivalently, approximate on the cubic spatial lattice. Axial, planar-diagonal, or body-diagonal finite-strength uniform fields are applied to n = 2 and 3 component cubic-spin spin-glass systems in d=3.
Citation Count: 1
Metastable Reverse-Phase Droplets Within Ordered Phases: Renormalization-Group Calculation of Field and Temperature Dependence of Limiting Size
(AMER PHYSICAL SOC, 2020) Eren, Ege; Berker, A. Nihat
Metastable reverse-phase droplets are calculated by renormalization-group theory by evaluating the magnetization of a droplet under magnetic field, matching the boundary condition with the reverse phase and noting whether the reverse-phase magnetization sustains. The maximal metastable droplet size and the discontinuity across the droplet boundary are thus calculated as a function of temperature and magnetic field for the Ising model in three dimensions. The method also yields hysteresis loops for finite systems, as function of temperature and system size.
Citation Count: 9
Devil's Staircase Continuum in the Chiral Clock Spin Glass With Competing Ferromagnetic-Antiferromagnetic and Left-Right Chiral Interactions
(Amer Physical Soc., 2017) Caglar, Tolga; Berker, A. Nihat
The chiral clock spin-glass model with q = 5 states with both competing ferromagnetic-antiferromagnetic and left-right chiral frustrations is studied in d = 3 spatial dimensions by renormalization-group theory. The global phase diagram is calculated in temperature antiferromagnetic bond concentration p random chirality strength and right-chirality concentration c. The system has a ferromagnetic phase a multitude of different chiral phases a chiral spin-glass phase and a critical (algebraically) ordered phase. The ferromagnetic and chiral phases accumulate at the disordered phase boundary and form a spectrum of devil's staircases where different ordered phases characteristically intercede at all scales of phase-diagram space. Shallow and deep reentrances of the disordered phase bordered by fragments of regular and temperature-inverted devil's staircases are seen. The extremely rich phase diagrams are presented as continuously and qualitatively changing videos.
Citation Count: 3
Frustrated Potts Model: Multiplicity Eliminates Chaos Via Reentrance
(Amer Physical Soc, 2020) Türkoğlu, Alpar; Berker, A. Nihat
The frustrated q-state Potts model is solved exactly on a hierarchical lattice, yielding chaos under rescaling, namely, the signature of a spin-glass phase, as previously seen for the Ising (q = 2) model. However, the ground-state entropy introduced by the (q > 2)-state antiferromagnetic Potts bond induces an escape from chaos as multiplicity q increases. The frustration versus multiplicity phase diagram has a reentrant (as a function of frustration) chaotic phase.
Citation Count: 11
Phase Transitions Between Different Spin-Glass Phases and Between Different Chaoses in Quenched Random Chiral Systems
(Amer Physical Soc., 2017) Çağlar, Tolga; Berker, A. Nihat
The left-right chiral and ferromagnetic-antiferromagnetic double-spin-glass clock model with the crucially even number of states q = 4 and in three dimensions d = 3 has been studied by renormalization-group theory. We find for the first time to our knowledge four spin-glass phases including conventional chiral and quadrupolar spin-glass phases and phase transitions between spin-glass phases. The chaoses in the different spin-glass phases and in the phase transitions of the spin-glass phases with the other spin-glass phases with the non-spin-glass ordered phases and with the disordered phase are determined and quantified by Lyapunov exponents. It is seen that the chiral spin-glass phase is the most chaotic spin-glass phase. The calculated phase diagram is also otherwise very rich including regular and temperature-inverted devil's staircases and reentrances.
Citation Count: 6
Lower Critical Dimension of the Random-Field Xy Model and the Zero-Temperature Critical Line
(Amer Physical Soc, 2022) Akin, Kutay; Berker, A. Nihat
The random-field XY model is studied in spatial dimensions d = 3 and 4, and in between, as the limit q -> infinity of the q-state clock models, by the exact renormalization-group solution of the hierarchical lattice or, equivalently, the Migdal-Kadanoff approximation to the hypercubic lattices. The lower critical dimension is determined between 3.81 < d(c) < 4. When the random field is scaled with q, a line segment of zero-temperature criticality is found in d = 3. When the random field is scaled with q(2), a universal phase diagram is found at intermediate temperatures in d = 3.
Citation Count: 1
Spin-S Spin-Glass Phases in the D=3 Ising Model
(Amer Physical Soc, 2021) Artun, E. Can; Berker, A. Nihat
All higher-spin (s >= 1/2) Ising spin glasses are studied by renormalization-group theory in spatial dimension d = 3, exactly on a d = 3 hierarchical model and, simultaneously, by the Migdal-Kadanoff approximation on the cubic lattice. The s-sequence of global phase diagrams, the chaos Lyapunov exponent, and the spin-glass runaway exponent are calculated. It is found that, in d = 3, a finite-temperature spin-glass phase occurs for all spin values, including the continuum limit of s -> infinity. The phase diagrams, with increasing spin s, saturate to a limit value. The spin-glass phase, for all s, exhibits chaotic behavior under rescalings, with the calculated Lyapunov exponent of lambda = 1.93 and runaway exponent of y(R) = 0.24, showing simultaneous strong-chaos and strong-coupling behavior. The ferromagnetic-spin-glass and spin-glass-antiferromagnetic phase transitions occurring, along their whole length, respectively at p(t) = 0.37 and 0.63 are unaffected by s, confirming the percolative nature of this phase transition.