How can plot with this specific option design? and if possible be better?

i want plot my phase portrait with this option and better of this if have any design please upload it

%% LGH Phase Portrait (Unperturbed) - Eq.(38) of the paper
% dU/dxi = phi
% dphi/dxi = (alpha^2*U - beta*U^3)/(1 - eps^2)
% First integral (Hamiltonian) Eq.(39) used for level curves.

clear; clc; close all;

%% Parameters (change these)
alpha = 1;        % alpha (paper uses alpha as parameter)
beta  = 1;        % beta
epsi  = 0.5;      % epsilon  (NOTE: avoid epsi^2 = 1)

den = (1 - epsi^2);
if abs(den) < 1e-12
    error('Choose epsilon such that 1 - epsilon^2 ~= 0');
end

%% Phase-plane grid
Umin = -3; Umax = 3;
Pmin = -3; Pmax = 3;   % P stands for phi

n = 35;
[U, P] = meshgrid(linspace(Umin,Umax,n), linspace(Pmin,Pmax,n));

dU = P;
dP = (alpha^2.*U - beta.*U.^3)/den;

%% Plot vector field (quiver) + streamlines
figure('Color','w'); hold on; box on;
quiver(U, P, dU, dP, 'AutoScale','on');
xlabel('U(\xi)'); ylabel('\phi(\xi)');
title('LGH Phase Portrait (Unperturbed)');

% Streamlines (optional but nice)
startU = linspace(Umin,Umax,10);
startP = linspace(Pmin,Pmax,10);
[sU, sP] = meshgrid(startU, startP);
streamline(U, P, dU, dP, sU(:), sP(:));

%% Equilibrium points from the paper
% E1=(0,0), E2=(sqrt(alpha/beta),0), E3=(-sqrt(alpha/beta),0)  (for beta>0)
plot(0,0,'ko','MarkerFaceColor','k','MarkerSize',6);

if beta > 0 && alpha/beta > 0
    ueq = sqrt(alpha/beta);
    plot( ueq, 0,'ko','MarkerFaceColor','k','MarkerSize',6);
    plot(-ueq, 0,'ko','MarkerFaceColor','k','MarkerSize',6);
end

%% Hamiltonian level curves (Eq. 39) to mimic the paper portraits
% H(U,phi) = phi^2/2 + beta*U^4/(4(1-eps^2)) - alpha^2*U^2/(2(1-eps^2)) + alpha^4/(4*beta*(1-eps^2)) = h
% (The constant shift does not change the shape; still we include it.)

H = 0.5*P.^2 + (beta.*U.^4)./(4*den) - (alpha^2.*U.^2)./(2*den) + (alpha^4)./(4*beta*den);

% Choose energy levels (you can edit these)
levels = [-2 -1 -0.5 0 0.5 1 2];
contour(U, P, H, levels, 'LineWidth', 1.2);

axis([Umin Umax Pmin Pmax]);
grid on;
hold off;

%% Example trajectories using ode45
% Provide some initial conditions and integrate forward/backward in xi
figure('Color','w'); hold on; box on;
contour(U, P, H, levels, 'LineWidth', 1.2);
xlabel('U(\xi)'); ylabel('\phi(\xi)');
title('Trajectories on Hamiltonian Level Curves');

f = @(xi,y) [ y(2);
              (alpha^2*y(1) - beta*y(1)^3)/den ];

xiSpanF = [0 50];
xiSpanB = [0 -50];

ICs = [ -2  0.5;
        -1  1.5;
         1  1.0;
         2 -0.5 ];

for k = 1:size(ICs,1)
    y0 = ICs(k,:)';
    [~,Yf] = ode45(f, xiSpanF, y0);
    [~,Yb] = ode45(f, xiSpanB, y0);
    plot(Yf(:,1), Yf(:,2), 'LineWidth', 1.5);
    plot(Yb(:,1), Yb(:,2), 'LineWidth', 1.5);
end

plot(0,0,'ko','MarkerFaceColor','k','MarkerSize',6);
if beta > 0 && alpha/beta > 0
    ueq = sqrt(alpha/beta);
    plot( ueq, 0,'ko','MarkerFaceColor','k','MarkerSize',6);
    plot(-ueq, 0,'ko','MarkerFaceColor','k','MarkerSize',6);
end

axis([Umin Umax Pmin Pmax]);
grid on;
hold off;

[dpb]

..."with this option..."

You neglected to tell us what "specific option" is...

If you nean to replicate the posted figure from the paper, it looks as though all that would be would be to use

subplot(1,3,i)

for i=1:3, creating each in turn.

[salim]

@dpb i want the design not make them 3 subplots i need the design of phase portrait!

[Star Strider]

Isn't it already a phase portrait? (Am I missing something?)